essay vitamins

Essay on Vitamins

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100 Words Essay on Vitamins

What are vitamins.

Vitamins are tiny helpers in our body that make sure we stay healthy. They help our body grow, heal, and even turn food into energy. We need to eat foods that have vitamins because our body cannot make enough of them on its own.

Types of Vitamins

There are two main types of vitamins: fat-soluble and water-soluble. Fat-soluble vitamins, like A, D, E, and K, get stored in our body’s fat. Water-soluble vitamins, like C and all the B vitamins, need to be taken in every day because our body doesn’t store them.

Why Vitamins Matter

Vitamins are essential for keeping our body working properly. They help us see in the dark, fight off colds, and keep our bones strong. Without enough vitamins, our body can get sick and not work the way it should.

250 Words Essay on Vitamins

What are vitamins.

Vitamins are a group of nutrients that our body needs to function properly. They help us to utilize the food we eat, turn food into energy, keep our immune system healthy, and protect cells from being damaged. Vitamins are classified as either water-soluble or fat-soluble. Water-soluble vitamins (vitamin C and B vitamins) are not stored in the body and need to be consumed daily. Fat-soluble vitamins (vitamins A, D, E, and K) are stored in the liver and fat tissues and can be stored for long periods.

Where can we find Vitamins?

What happens if we don’t get enough vitamins.

If we don’t get enough vitamins, we can develop vitamin deficiency diseases. For example, vitamin C deficiency can cause scurvy, vitamin D deficiency can cause rickets, and vitamin A deficiency can cause night blindness. Vitamin deficiency diseases can be serious, so it is essential to make sure we get enough vitamins from our diet.

Vitamins are essential nutrients that our body needs to function properly. We can get vitamins from a variety of foods, and it is essential to eat a variety of foods to make sure we get all the vitamins our body needs.

500 Words Essay on Vitamins

Vitamins are substances that our bodies need to function properly. They help us grow, develop, and stay healthy. Vitamins can be found in the foods we eat. There are two main types of vitamins: water-soluble vitamins and fat-soluble vitamins.

Water-Soluble Vitamins

Water-soluble vitamins are vitamins that dissolve in water. They include vitamin C and the B vitamins. Water-soluble vitamins are not stored in the body, so we need to eat foods that contain them every day.

Fat-Soluble Vitamins

Fat-soluble vitamins are vitamins that dissolve in fat. They include vitamins A, D, E, and K. Fat-soluble vitamins are stored in the body, so we do not need to eat foods that contain them every day.

Functions of Vitamins

Sources of vitamins.

The best way to get vitamins is to eat a healthy diet that includes a variety of foods. Fruits, vegetables, and whole grains are all good sources of vitamins. Meat, fish, and eggs are also good sources of vitamins.

Vitamin Deficiency

A vitamin deficiency is a condition that occurs when the body does not get enough of a particular vitamin. Vitamin deficiencies can be caused by a number of factors, including a poor diet, certain medical conditions, and medications. Vitamin deficiencies can lead to a variety of health problems, including fatigue, weakness, and skin problems.

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This chapter is going to explain a part of the nutrients the human body needs. They are organic compounds called vitamins. Those compounds will be clarified, as well as their benefits, deficiencies, chemical structure, and why the body needs them crucially. Vitamins is an exceptionally vital recognized name required in certain amounts in the body, some of them exist as a complicated natural compounds found in herbal meals. It plays a key function in regular metabolism, the absence of which in the diet causes deficiency and several diseases. Vitamins are differentiated from the trace elements, also found in the weight-reduction plan in small quantities for health, growth, replica, and other crucial metabolism.

water-soluble vitamins
fat-soluble vitamins

Author Information

Mohanad mousa kareem *.

Department of Chemistry, College of Science, University of Babylon, Iraq

Majid S. Jabir

Division of Biotechnology, Department of Applied Science, University of Technology, Iraq

*Address all correspondence to: [email protected]

1. Introduction

The human body is a magnificent machine, and to function well, the body needs certain supplements. Vitamins are one of the most essential elements for the body. There are nutrients that the body can make on its own, and there are others that the body is not able to make. Vitamins are one of the nutrients that the body is unable to make, so they must be consumed from aliments. Vitamins are an organic molecule, which is an essential micronutrient that an organism needs for its metabolism to function. They are divided into two groups, fat-soluble vitamins and water-soluble vitamins. The first group contains vitamins A, D, E, and K, while the second consists of thiamin (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), pyridoxal, pyridoxamine, pyridoxine (B6), biotin-cobalamin (B12), folic acid, and ascorbic acid [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ].

2. Fat-soluble vitamins

They are a type that is absorbed well into the blood stream via fatty nourishments and are stored in limited amounts; they can be easy to separate and disposed out from the body through urine [ 8 , 9 , 10 ].

2.1 Vitamin A

Vitamin A is a yellow viscous liquid alicyclic alcohol C 20 H 30 O that contains one more double bond in a molecule than vitamin A1 and is less active biologically in mammals and that occurs especially in the liver oil of freshwater fish. It consists of three biologically active molecules, retinol, retinal (retinaldehyde), and retinoic acid, all derived from the plant precursor molecule, β-carotene ( Figure 1 ) [ 11 , 12 ].

Types of vitamin A.

Retinol also functions in the synthesis of certain glycoproteins and mucopolysaccharides necessary for mucous production and normal growth regulation. Retinol is the predominant, active form of vitamin A found in the blood. Retinyl palmitate is the storage form of the vitamin [ 13 ].

This vitamin is important to the body for playing an effective role in growth and development, the visual system, immunity, and reproduction as well as supplying epithelial cellular integrity. Most of the vitamin A is stored in the liver in the form of retinyl esters. Sources of vitamin A vary from vegetables to fruits and are found in animal-sourced foods, such as eggs, oily fish, liver, cheese, and butter. The lack of this vitamin can leave severe effects on the function of the body such as night blindness, decreased resistance to infections, and extremely dry skin, hair, or nails. Just deficiency can be harmful; the overuse of vitamin A can be toxic and lead to hypervitaminosis. An average dose of this vitamin needed for the body is 0.7 mg for men and 0.6 mg for women on a daily diet. Women who have been through menopause and older men, who are more at risk of osteoporosis, should avoid having more than 1.5 mg of vitamin A per day from food and supplements [ 7 , 13 , 14 ].

2.2 Vitamin D

Vitamin D is a steroid vitamin, which promotes the intestinal absorption and metabolism of calcium and phosphorus. There are two main types of vitamin D, Vitamin D 2 , which is synthesized by plants and is not created by the human body. Vitamin D 3 , which is made in large amounts in the skin when daylight strikes uncovered skin. Moreover, it can be ingested from animal sources. As well as there other types like ergosterol, dehydrocholesterol, and the biologically active form of the hormone 1,25-dihydroxy vitamin D 3 termed calcitriol.

Vitamin D is not active itself (it is a prohormone); it is modified to yield biologically active forms, such as calcitriol. Calcitriol (derived from vitamin D) is a transcription factor, influencing expression of proteins involved in calcium absorption and transport [ 15 , 16 , 17 ] ( Figure 2 ).

Types of vitamin D.

Vitamin D is required to maintain normal blood levels of calcium and phosphate, which in turn is needed for the normal mineralization of the bone, muscle contraction, nerve conduction, general cellular function in all cells of the body and supporting lung function, and cardiovascular health. It may also protect against a range of diseases and conditions, such as type 1 diabetes. Vitamin D also modulates the transcription of cell cycle proteins, which decrease cell proliferation and increase cell differentiation of a number of specialized cells of the body (e.g., osteoclastic precursors, enterocytes, and keratinocytes). This property may explain the actions of vitamin D in bone resorption, intestinal calcium transport, and skin. Vitamin D also possesses immunomodulatory properties that may alter responses to infections in vivo. These cell-differentiating and immunomodulatory properties underlie the reason why vitamin D derivatives now are in use successfully in the treatment of psoriasis and other skin disorders. Oily fish, such as salmon, sardines, herring, and mackerel, contain a fair amount of vitamin D as well as red meat, liver, egg yolks, and fortified foods, such as most fat spreads and some breakfast cereals. Another source of vitamin D is dietary supplements [ 15 , 16 , 17 , 18 ].

The simplest way to get all the vitamin D the body needs is from direct sunlight. The absence of this very vitamin in an adult daily diet can result in hypovitaminosis D, which leads to loss of bone density, which can contribute to osteoporosis and fractures (broken bones). In children, a severe vitamin D deficiency can cause delays in growth as well as rickets, a disease where the bones become soft and bend. Furthermore, vitamin D deficiency has been in link with several cancers, type 1 diabetes, multiple sclerosis, high blood pressure, and thyroid problems. A daily dose of vitamin D 1000 IU should prevent very low vitamin D levels and should be sufficient to help most aging adults get the benefit [ 17 , 18 , 19 ].

2.3 Vitamin E

Vitamin E is a major lipid-soluble antioxidant in the cell’s antioxidant defense system and is exclusively obtained from the diet. The term “vitamin E” refers to a family of eight naturally occurring homologs synthesized by plants from homogentisic acid. All are derivatives of 6-chromanol and differ in the number and position of methyl groups on the ring structure known as tocopherols ( Figure 3 ) [ 20 ].

This particular vitamin plays a huge role in protecting cell membranes and other fat-soluble parts of the body (LDL cholesterol) from oxidation; it also may reduce the risk of heart disease, discourage development of some types of cancer, promote normal growth and development, and promote normal red blood cell formation. It can also act as an anti-blood clotting agent and plays some role in the body’s ability to process glucose. In addition, it is recognized to aid the process of wound healing. This vitamin is found in wheat germ oil, vegetable oils, nuts and seeds, whole grains, and egg yolk, in addition to leafy green vegetables [ 21 , 22 ].

Vitamin E is mainly stored in the liver before released into the blood stream for use. Vitamin E is essential to the central nervous system. It is among the body’s main antioxidants, and a deficiency results in oxidative stress, which can lead to muscle weakness. A deficiency can cause certain neurons, called the Purkinje neurons, to break down, harming their ability to transmit signals, which causes walking difficulties. Numbing and tingling also is a sign of deficiency, and the damage to nerve fibers can prevent the nerves from transmitting signals correctly, resulting in these sensations, which is also called peripheral neuropathy. The deficiency can also cause weakness of light receptors in the retina and other cells in the eye, and this can lead to loss of vision over time as well as immune system problems. The recommended daily dosage of this vitamin for males is 30 IU and for females 24 IU [ 22 , 23 , 24 ].

2.4 Vitamin K

Vitamin K refers to a group of chemically similar fat-soluble compounds called naphthoquinones: vitamin K1 (phytonadione) is found in plants and is the primary source of vitamin K for humans through dietary consumption, vitamin K2 compounds (menaquinones) are made by bacteria in the human gut, and vitamin K3 (menadione) is a water-soluble preparation available for adults only ( Figure 4 ). Vitamin K is necessary for the liver to produce the coagulation factors II, VII, IX, and X as well as the clotting factors protein C, protein S, and protein Z [ 25 , 26 ].

Types of vitamin K.

The body needs vitamin K to produce prothrombin, a protein and clotting factor that is important in blood clotting and bone metabolism. Vitamin K1, or phylloquinone, comes from plants. It is the main type of dietary vitamin K. A lesser source is vitamin K2, or menaquinones, which occurs in some animal-based and fermented foods. The body is in need for both types of vitamin K to produce prothrombin, a protein that plays crucial roles in blood clotting, bone metabolism, and heart health. Vitamin K also helps facilitate energy production in the mitochondria of cells. Vitamin K has antioxidant properties. It protects cellular membranes from damage due to excess free radicals, in a process known as peroxidation. It is in use in synthesizing gamma-carboxyglutamate, a posttranslationally modified amino acid in prothrombin. Green vegetables contain the highest amounts of vitamin K like kale, spinach, turnip greens, collards, and green leaf lettuce vegetables, but there are many other good sources like fish, liver, meat, eggs, and cereals (contain smaller amounts). Vitamin K is made as well by the bacteria in the lower intestinal tract. Vitamin K deficiency is very rare. It occurs when the body does not properly absorb the vitamin from the intestinal tract. Vitamin K deficiency can also occur after long-term treatment with antibiotics. In adults, primary vitamin K-deficient states that manifest as bleeding are almost unknown, except when the absorption of the vitamin is impaired, resulting in an underlying pathology. Vitamin K deficiency bleeding is a problem that occurs in some newborns. It happens during the first few days of life. This condition used to be named hemorrhagic disease of the newborn. About toxicity, natural vitamin K seems free of toxic side effects. This apparent safety is designated out by the common clinical administration of phylloquinone at doses of 10–20 mg or greater. The recommended daily dosage for male adults is 120 mcg and for female adults is 90 mcg [ 26 , 27 , 28 , 29 ].

3. Water-soluble vitamins

3.1 thiamin (b1).

Thiamin is one of the B vitamins. The B vitamins are a group of water-soluble vitamins that are part of many of the chemical reactions in the body. It plays a role by producing energy from carbohydrates and helping in proper nerve function as well as stabilizing the appetite and promoting growth and good muscle tone. It is also involved in the flow of electrolytes into and out of muscle and nerve cells. Thiamin is rapidly converted to its active form, thiamin pyrophosphate (TPP) ( Figure 5 ), in the brain and liver by specific enzymes, thiamine phosphotransferase [ 30 , 31 ].

Types of vitamin B1.

There are many natural ways to add thiamine-rich foods to an everyday diet. Food sources of thiamine include beef, liver, dried milk, nuts, oats, oranges, pork, eggs, seeds, legumes, peas, and yeast. Foods also are fortified with thiamine. Some foods that are fortified with B1 are rice, pasta, breads, cereals, and flour. The relieving thing about thiamin is that it’s non-toxic even at high dosage. However, the deficiency can be worrying because it leads to loss of appetite, weakness, and tiredness. Also causes insomnia, loss of weight, in addition to depression and gastrointestinal problems. Moreover, the deficiency leads to neurological problems and beriberi, which is a muscle atrophy. Furthermore, we must mention Wernicke-Korsakoff syndrome, which is a disease most commonly found in chronic alcoholics due to their poor dietetic lifestyles. A recommended daily dosage of thiamin for body requirement is 1.0–1.5 mg for normal adults [ 32 , 33 , 34 ].

3.2 Riboflavin (B2)

Vitamin B2 is an organic compound that is not stored by the body except in insignificant amounts. It must be replenished daily. It is the precursor of coenzymes flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) ( Figure 6 ). The enzymes that require FMN or FAD and FADH 2 as cofactors are termed flavoproteins. Several flavoproteins also contain metal ions, termed metalloflavoproteins. It contributes in energy production carbohydrate, fat, and protein metabolism and also in the formation of antibodies and red blood cells, not to mention respiration and maintenance of good vision and alleviating skin, nails, and hair, plus improving eye fatigue [ 35 , 36 , 37 ].

Types of vitamin B2.

Riboflavin decomposes when exposed to visible light. This characteristic can lead to riboflavin deficiencies in newborns treated for hyperbilirubinemia by phototherapy. Sources of riboflavin are present in large amounts in meat, fish, eggs, vegetables, dairy foods, and grain products. The deficiency of B2 is common due to poor diet. The resulting side effects of the deficiency of riboflavin are itching, burning eyes, cracks and sores in mouth and lips. In addition to bloodshot eyes, dermatitis, oily skin, and digestive disturbances. Moreover, normocytic anemia is associated with pure red cytoplasia of the bone marrow. The toxicity of this vitamin is not an issue due to limited intestinal absorption. The required daily dosage of B2 for adolescent and adults is 1.0–1.3 mg [ 10 , 37 , 38 ].

3.3 Niacin (B3)

Niacin (nicotinic acid and nicotinamide), or known as vitamin B3, is required for the synthesis of the active forms of vitamin B3, nicotinamide adenine dinucleotide (NAD+), and nicotinamide adenine dinucleotide phosphate (NADP+). Both NAD+ and NADP+, also known as NADPH (reduced form), function as cofactors for numerous dehydrogenases ( Figure 7 ) [ 38 , 39 ].

Structures of NADH, NAD + , NADPH, and NADP + .

Niacin is an essential nutrient required for normal metabolism, energy production, maintenance of skin and tongue, and also improvement of circulation and maintenance of nervous system as well as the health of the digestive tract. This vitamin is divided into two types, nicotinic acid and niacinamide (nicotinamide) ( Figure 8 ). It helps build proteins in the skin and lock in moisture to prevent environmental damage. The use is frequent in cosmetics and personal care products due to its wonderful effectiveness and treatments to skin and hair flaws and problems. It is important to mention that niacin is highly toxic in large doses and can lead to no good; doses of only 50–100 mg nicotinic acid can cause dilation of blood vessels and potentially painful tingling (“niacin flush”), diarrhea, nausea, vomiting, and long-term liver damage. In spite of the danger, nicotonic acid regulates the cholesterol with the assistance of inositol hexaniacinate, which is a supplement that regulates cholesterol without high toxicity. Nicotinamide is nearly always safe to take, although a few cases of liver damage have been in report due to doses of over 1000 mg/day [ 10 , 39 ].

Types of B3.

This vitamin is consumed through meat like liver, fish, and pork and peanuts, whole wheat, brown rice, mushrooms, and vegetables like green peas and potatoes, as well as fruits that are enriched in B3 like avocado. Deficiency can lead to pellagra, which is a dangerous disease. The symptoms are marked by dementia, diarrhea, and dermatitis, also known as “the three Ds.” If left untreated, pellagra can be fatal. Besides pellagra, deficiency causes gastrointestinal disturbance, loss of appetite, headache, insomnia, and mental depression. Moreover, it can be the reason of fatigue, aches, pains, nervousness, and irritability. The recommended daily dosage of a stable diet for vitamin B3 is 16 mg/day for males +14 years and for females +14 years 14 mg/day [ 39 , 40 , 41 ].

3.4 Pantothenic acid (B5)

Pantothenic acid ( Figure 9 ) is vitamin B5. The word pantothenic comes from the Greek “pantou,” meaning everywhere. Nearly all foods contain small quantities of pantothenic acid. It is one of the eight water-soluble B vitamins, which enables the body to break down carbohydrates into glucose to produce energy and to make red blood cells. This acid is formed from ß-alanine and pantoic acid. Pantothenic acid is required for the synthesis of coenzyme A (CoA) and component of the acyl carrier protein (ACP) domain of fatty acid synthase, in addition to its need for the metabolism of carbohydrate by the TCA cycle and all fats and proteins [ 38 , 42 ].

Vitamin B5.

Moreover, vitamin B5 also takes action in converting food into glucose, synthesizing cholesterol and forming sex and stress-related hormones in the adrenal glands. In addition, vitamin B5 helps maintain healthy skin, hair, eyes, and digestive system and also assists the body in using other vitamins. Furthermore, it can be in use for skin care as some studies have shown that vitamin B5 works as a moisturizer on the skin and enhances the healing process of skin wounds and acne. In addition, some studies suggest that vitamin B5 intake can help lower cholesterol and levels of blood triglycerides or fats. Almost all plant- and animal-based foods contain pantothenic acid in varying amounts, though food processing can cause a significant loss. Vitamin B5 is mainly found in members of the cabbage family, poultry, white and sweet potatoes, whole-grain cereals, and yeast, in addition to milk, lentils, and legumes. Deficiency is rare but can cause symptoms like headache, fatigue, irritability, impaired muscle coordination, gastrointestinal problems, and paresthesia, which is a tingling and numbing feeling in the feet, hands, legs, and other parts of the body. The recommended daily intake for this acid is 1.7–5.0 mg; large doses of pantothenic acid do not cause symptoms, other than possible diarrhea [ 43 , 44 ].

3.5 Pyridoxal, pyridoxamine, and pyridoxine (B6)

Pyridoxine is one of the vitamin B6 groups which also includes pyridoxal and pyridoxamine; all three compounds are efficiently converted by pyridoxal kinase to the biologically active form of vitamin B6, which is pyridoxal phosphate ( Figure 10 ). Pyridoxal phosphate functions as a coenzyme, a substance that enhances the action of an enzyme and thereby helps catalyze and speed a biochemical reaction [ 38 , 45 ].

Types of vitamin B6.

Vitamin B6 is important to the body for it plays a huge role in the production of red blood cells, the conversion of tryptophan to niacin (B3), and the immunity and nervous system functions. Moreover, it reduces muscle spasms, cramps, and numbness as well as maintains a proper balance of sodium and phosphorus in the body. Good sources of this vitamin is just like most other vitamins, it can be found in whole-grain cereals, eggs, vegetables, soya beans, peanuts, milk, and potatoes as well as meat like poultry, pork, and fish. The risks of the deficiency are rare but can lead to nervousness, insomnia, loss of muscle control, muscle weakness, and arm and leg cramps, in addition to water retention and skin lesions. The recommended daily dosage of this vitamin is 1.4 mg a day for men and 1.2 mg a day for women [ 38 , 45 , 46 ].

3.6 Biotin-cobalamin (B12)

Biotin is a water-soluble B-complex vitamin that helps the body metabolize proteins and process glucose. Biotin is also known as vitamin B7 or vitamin H ( Figure 11 ). It is also involved in the metabolism of fatty acids, a type of molecule found in fats and oils and leucine, an essential amino acid that humans cannot synthesize [ 46 ].

Vitamin B12 (biotin).

Biotin has a number of benefits to the human body like lowering cholesterol, regulating blood sugar, improving the skin health, as well as strengthening hair and nails. A research has found that biotin can treat multiple sclerosis, a serious disease that affects the central nervous system, if taken in high doses as studies have shown. Biotin is largely found in egg yolks, cheese, legumes such as soybeans and peanuts, leafy greens, and cauliflower. Moreover, it also exists in mushrooms, nuts and nut butters, as well as animal liver and kidney. Biotinidase deficiency (BTD) is the most common cause of biotin deficiency. BTD is a rare inherited disorder where the body is not able to use biotin and leads to biotin deficiency, which developed by a mutation in the BTD gene. This gene instructs the body on how to make the enzyme biotinidase, which the body needs to extract biotin from food. Biotin deficiency includes thinning hair, progressing to loss of hair across the body, and a scaly, red rash around body openings, including the eyes, nose, mouth, and anus, as well as development of conjunctivitis. The daily requirement of this vitamin is within 5–30 mcg, for both men and women; the dosage differs according to age [ 47 , 48 ].

Cobalamin is an essential nutrient and natural water-soluble vitamin of the B-complex family that must combine with an intrinsic factor for absorption by the intestine; vitamin B12 (cyanocobalamin) ( Figure 12 ) is necessary for hematopoiesis, which is the process by which blood cells are formed and neural, in addition to metabolism, DNA and RNA production, as well as carbohydrate, fat, and protein metabolism. B12 improves iron functions in the metabolic cycle and assists folic acid in choline synthesis. B12 metabolism is interconnected with that of folic acid. This vitamin is mainly found in meat, for instance, fish, clams, beef, animal liver and kidney, as well as in eggs, dairies, and fortified nutritional yeast. Deficiency of cobalamin results to anemia, nerve damage, and hypersensitive skin. The recommended daily requirement of this vitamin for men and women of +14 of age is 2–3 mcg/day [ 47 , 48 , 49 ].

Vitamin B12 (cobalamin).

3.7 Folic acid (B9)

Folic acid is a form of vitamin B9 that can dissolve in water. It is a key ingredient in the making of the nucleic acid, which forms part of all genetic material. Its main functions are synthesis and repair of DNA and RNA, aiding rapid cell division and growth, enhancing brain health, and age-related hearing loss ( Figure 13 ) [ 50 ].

Vitamin B9.

Folic acid is essential to the body, and the deficiency of it can cause anemia, diseases of the heart and blood vessels and defects in the brain and spinal cord in a fetus. Folic acid is added to be in study with vitamin B12 in the prevention and treatment of cancer. It is also called folate. In addition, it is in consideration that folic acid plays a preventive role in a number of conditions like autism; a recent study connected folic acid deficiency with autism. It is fair to mention that folic acid is often used to support a methotrexate prescription for rheumatoid arthritis, which is a long-term, progressive, and disabling autoimmune disease. It causes inflammation, swelling, and pain in and around the joints and other body organs. This vitamin can be consumed through legumes, eggs, leafy greens, asparagus, beetroot, citrus fruits, beef liver, wheat germ-fortified grains, and others. The required daily dosage for the body is 0.1–0.4 mg [ 51 , 52 ].

3.8 Ascorbic acid (vitamin C)

Vitamin C is also known as ascorbic acid, a water-soluble vitamin, one that is not able to be in storage by the body except in insignificant amounts. It must be replenished daily. It helps produce collagen, a protein needed to develop and maintain healthy teeth, bones, gums, cartilage, vertebrae discs, joint linings, skin, and blood vessels. Vitamin C is a powerful antioxidant that protects your cells from damage by free radicals produced by cigarette smoke, air pollution, excessive sunlight, and normal metabolism ( Figure 14 ). Free radicals are considered to play a role in rapid aging and diseases such as cancer and heart disease [ 53 , 54 , 55 ].

It known that vitamin C helps metabolize proteins and its antioxidant activity may have a chance of reducing the risk of some cancers. Scurvy is the name for a vitamin C deficiency which results in anemia, fatigue, depression, and connective tissue defects like internal bleeding, petechiae, impaired wound healing, and gingivitis. Vitamin C is mainly found in citrus fruits such as orange, kiwi, lemon, guava, and grapefruit, and vegetables such as broccoli, cauliflower, Brussels sprouts, and capsicums are rich, natural sources of vitamin C. Other vitamin C-rich fruits include papaya, cantaloupe, and strawberries. The required intake of the vitamin is 45–60 mg for male and female, and the dosage differs according to age [ 54 , 55 , 56 , 57 , 58 ].

4. Conclusions

In conclusion, there are two types of vitamins, which are essential to the body, water-soluble vitamins and fat-soluble vitamins; both types play an effective part in the human body. Nobody can deny the necessity of these vitamins to the body in all ages, and the lack of it can result in severe damage in certain parts of the body according to which vitamin and age as well as the health status of each person.

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29. Conly JM, Stein K. Quantitative and qualitative measurements of K vitamins in human intestinal contents. The American Journal of Gastroenterology. 1992; 87 :311-316
30. Said HM. Thiamin. In: Coates PM, Betz JM, Blackman MR, et al., editors. Encyclopedia of Dietary Supplements. 2nd ed. Informa Healthcare: London and New York; 2010. pp. 748-753
31. Bemeur C, Butterworth RF. Thiamin. In: Ross AC, Caballero B, Cousins RJ, Tucker KL, Ziegler TR, editors. Modern Nutrition in Health and Disease. 11th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2014. pp. 317-324
32. Gibson GE, Blass JP. Thiamine-dependent processes and treatment strategies in neurodegeneration. Antioxidants & Redox Signaling. 2007; 9 :1605-1619
33. McCormick DB. Thiamin. In: Shils ME, Young VR, editors. Modern Nutrition in Health and Disease. 6th ed. Philadelphia, PA: Lea & Febiger; 1988. pp. 355-361
34. Bailey AL et al. Thiamin intake, erythrocyte transketolase (EC 2.2.1.1) activity and total erythrocyte thiamin in adolescents. British Journal of Nutrition. 1994; 72 :111-125
35. Rivlin RS. Riboflavin. In: Coates PM, Betz JM, Blackman MR, et al., editors. Encyclopedia of Dietary Supplements. 2nd ed. Informa Healthcare: London and New York; 2010. pp. 691-699
36. Said HM, Ross AC. Riboflavin. In: Ross AC, Caballero B, Cousins RJ, Tucker KL, Ziegler TR, editors. Modern Nutrition in Health and Disease. 11th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2014. pp. 325-330
37. Neugebauer J, Zanre Y, Wacker J. Riboflavin supplementation and preeclampsia. International Journal of Gynaecology and Obstetrics. 2006; 93 :136-137
38. Food and Nutrition Board. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic acid, Biotin, and Choline. Washington, DC: National Academy Press; 1998
39. Penberthy WT, Kirkland JB. Niacin. In: Erdman JW, Macdonald IA, Zeisel SH, editors. Present Knowledge in Nutrition. 10th ed. Washington, DC: Wiley-Blackwell; 2012. pp. 293-306
40. Kirkland JB. Niacin. In: Ross AC, Caballero B, Cousins RJ, Tucker KL, Ziegler TR, editors. Modern Nutrition in Health and Disease. 11th ed. Baltimore, MD: Williams & Wilkins; 2014. pp. 331-340
41. MacKay D, Hathcock J, Guarneri. Niacin: Chemical forms, bioavailability, and health effects. Nutrition Reviews. 2012; 70 :357-366
42. Miller JW, Rucker RB. Pantothenic acid. In: Erdman JW, Macdonald IA, Zeisel SH, editors. Present Knowledge in Nutrition. 10th ed. Washington, DC: Wiley-Blackwell; 2012. pp. 375-390
43. Sweetman L. Pantothenic acid. In: Coates PM, Betz JM, Blackman MR, et al., editors. Encyclopedia of Dietary Supplements. 2nd ed. Informa Healthcare: London and New York; 2010. pp. 604-611
44. Trumbo PR. Pantothenic acid. In: Ross AC, Caballero B, Cousins RJ, et al., editors. Modern Nutrition in Health and Disease. 11th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2014. pp. 351-357
45. Mackey A, Davis S, Gregory J. Vitamin B6. In: Shils M, Shike M, Ross A, Caballero B, Cousins R, editors. Modern Nutrition in Health and Disease. 10th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2005
46. Riggs KM, Spiro A 3rd, Tucker K, Rush D. Relations of vitamin B-12, vitamin B-6, folate, and homocysteine to cognitive performance in the normative aging study. The American Journal of Clinical Nutrition. 1996; 63 :306-314
47. Herbert V. Vitamin B12 in Present Knowledge in Nutrition. 17th ed. Washington, DC: International Life Sciences Institute Press; 1996
48. Herbert V, Das K. Vitamin B12 in Modern Nutrition in Health and Disease. 8th ed. Baltimore, MD: Williams & Wilkins; 1994
49. Combs G. Vitamin B12 in the Vitamins. New York: Academic Press, Inc.; 1992
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51. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes: Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academy Press; 1998
52. Scott JM, Weir DG. Folate/vitamin B12 interrelationships. Essays in Biochemistry. 1994; 28 :63-72
53. Gershoff SN. Vitamin C (ascorbic acid): New roles, new requirements? Nutrition Reviews. 1993; 51 :313-326
54. Rebouche CJ. Ascorbic acid and carnitine biosynthesis. American Journal of Clinical Nutrition. 1991; 54 (Suppl):S1147-S1152
55. McCormick DB, Zhang Z. Cellular assimilation of water-soluble vitamins in the mammal: Riboflavin, B6, biotin and C. Proceedings of the Society of Experimental Biology and Medicine. 1993; 202 :265-270
56. Bates CJ. Bioavailability of vitamin C. European Journal of Clinical Nutrition. 1997; 51 (Suppl 1):S28-S33
57. Kareem MM, Baqir SJ, Aowda SA, Hussein FA. Determination of vitamin C (ascorbic acid) concentration in some of commercial products, by redox titration. UOB Journal of Pure & Applied Sciences. 2010; 3 :18
58. Kareem MM. Chemistry of Fruits. Jordan: DAR SAFA Publishing-Distributing; 2020. ISBN: 978-9923-28-014-0

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Essay on Vitamin A: Top 7 Essays | Nutrition | Living Organisms | Biology

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Here is an essay on ‘Vitamin A’ for class 7, 8, 9, 10, and 11, and 12. Find paragraphs, long and short essays on ‘Vitamin A’ especially written for school and college students.

Essay on Vitamin A

Essay Contents:

Essay on the Deficiency of Vitamin A

Essay # 1. Historical Review of Vitamin A:

In 1912 Hopkins reported normal and continued growth when whole milk was added to purified rations in young rats, and this study ultimately led up to the discovery of this vitamin by McCollum. In 1915 McCollum and Davis established the essential factors in eggs, butter and milk, i.e., ‘fat-soluble A’ in eggs and butter, and ‘water-soluble B’ in milk. ‘Fat-soluble A’ cured Xerophthalmia.

Includes A 1 and A 2 . A 2 is functionally almost similar to A 1 . Chemical structure is slightly different. Vitamin A 2 has one more double-bond. It is a dehydrovitamin A 1 and also known as 3-dehydroretinal. Its potency is 40% that of vitamin A 1 . Vitamin A 1 may be derived from β-carotene by cleavage at the midpoint of the carotene molecule.

Essay # 2. Chemical Structure of Vitamin A:

Unsaturated primary alcohol (-ioninol). Empirical formula of vitamin A 1 (retinol 1 ) is C 20 H 29 OH and of vitamin A 2 (retinol 2 ) is C 20 H 27 OH. Structure closely similar to plant pigments carotenes, the pro-vitamin A.

Since β-ionone ring is essential part of vitamin A molecule and as β-carotene contains two β-ionone rings and α- and γ-carotenes contain β-ionone ring, so α- and γ-carotenes give one molecule of vitamin A but β-carotene gives two.

The chemical structure of β-carotene, vitamins A 1 and A 2 are shown below:

b. Degeneration of lachrymal glands.

c. Redness, abnormally dry and lusterless condition of the eye-ball (Xerophthalmia) (Fig. 11.2) with consequent keratinization and degeneration of cornea (Keratomalacia).

iii. Epithelial Tissues:

Thickening and keratinisation, follicular and popular eruptions (Phrynoderma or Toad skin), sebaceous and sweat glands degenerate.

b. Alimentary Tract:

The glands present in the alimentary tract and the epithelial linings degenerate.

c. Kidney and Urinary Tract:

Epithelium degenerates and becomes cornified, hence favours formation of renal stone.

d. Respiratory Passages:

The Epithelium becomes stratified and degenerates.

Mentioned above.

These degenerative changes of the epithelial tissues decrease the resistance of the local cells, hence infection in these regions easily takes place. For this reason vitamin A is called anti-infective vitamin.

iv. Nervous System:

Degeneration of the nervous system specially affecting the afferent tracts (resembles subacute combined degeneration). Retina also shows degenerative changes.

Abnormal bone growth in certain parts of vertebral column and skull. It is believed that effects on nervous system are partly due to the abnormal type of growth giving pressure effect on nerves.

vi. Reproduction:

In rats reproduction becomes defective. Interferes with the normal process of ovulation although it is not proved in man.

International Unit:

Equivalent to the activity of 0.6 micro-gram of carotene (same as 0.344 micro-gram of pure preparation of vitamin A 1 acetate).

Daily Requirement:

5,000 i.u. for adults. For growing children and during puberty, lactation and pregnancy—6,000-8,000 i.u.

Hypervitaminosis A:

In growing rats large doses (4,000 units per day) cause:

i. Loss of weight.

ii. Atrophy of skin.

iii. Loss of hair.

iv. Ulcerations in the eyes.

v. Haemorrhage.

vi. Decalcification of bones with spontaneous fracture.

vii. Lowering of plasma prothrombin.

viii. Reduction of ascorbic acid content of the tissues.

Administration of vitamins K and C prevents these changes of hypervitaminosis A. Effects in man include drowsiness, sluggishness, severe headache, vomiting and peeling of skin of mouth and elsewhere.

Vitamin Interrelationship:

The haemorrhagic manifestations associated with hypervitaminosis may be prevented by simultaneous administration of vitamin K. The effect may be due to interference with bacterial synthesis of vitamin K in the intestine. The antioxidant action of tocopherols is probably responsible for its sparing action on vitamin A and carotene. This protective effect of vitamin E is enhanced by other antioxidants, e.g., ascorbic acid, etc.

Essay on Vitamin D: Top 6 Essays | Nutrition | Living Organisms | Biology
Essay on Vitamin E: Top 5 Essays | Nutrition | Living Organisms | Biology

Essay , Biology , Living Organisms , Nutrition , Vitamins , Fat-Soluble Vitamin , Vitamin A

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Adv Pharm Bull
v.6(4); 2016 Dec

Vitamins, Are They Safe?

Hadi hamishehkar.

1 Drug Applied Research Center, Tabriz University of Medical Sciences, Tabriz, Iran.

Farhad Ranjdoost

2 Iranian Evidence Based Medicine Center of Excellence, Tabriz University of Medical Sciences, Tabriz, Iran.

Parina Asgharian

3 Student Research Committee, Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran.

Ata Mahmoodpoor

4 Department of Anesthesiology and Intensive Care, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran.

Sarvin Sanaie

5 Tuberculosis & Lung Disease Research Center, Tabriz University of Medical Sciences, Tabriz, Iran.

The consumption of a daily multivitamin among people all over the world is dramatically increasing in recent years. Most of the people believe that if vitamins are not effective, at least they are safe. However, the long term health consequences of vitamins consumption are unknown. This study aimed to assess the side effects and possible harmful and detrimental properties of vitamins and to discuss whether vitamins can be used as safe health products or dietary supplements. We performed a MEDLINE/PubMed, EMBASE, Scopus and Google Scholar search and assessed reference lists of the included studies which were published from 1993 through 2015. The studies, with an emphasis on RCTs (randomized controlled clinical trials), were reviewed. As some vitamins such as fat-soluble vitamins (vitamin A, vitamin D, vitamin E), and also some of the water-soluble vitamins like folic acid may cause adverse events and some like vitamin C is widely taken assuming that it has so many benefits and no harm, we included relevant studies with negative or undesired results regarding the effect of these vitamins on health.

Our recommendation is that taking high-dose supplements of vitamins A, E, D, C, and folic acid is not always effective for prevention of disease, and it can even be harmful to the health.

Introduction

Most people all over the world use a daily multivitamin for treatment or prevention of chronic disease. Uncontrolled advertisements about the vitamins in addition to wide availability of these agents result in high prevalence of their consumption among people. Although the effectiveness of the multivitamins and minerals is unclear, the prevalence of the use of these supplements in many developed countries is widened. 1 The percentage of adults using any daily vitamin and mineral supplement has increased very rapidly in recent years. One third of adults and half of population aging more than 55 years report taking of at least one supplement per day. 2 An increase in supplement sales has been seen since 1997, reaching to $18.8 billion in the United States in 2003. 3

Antioxidants such as α-tocopherol (vitamin E), ascorbic acid (vitamin C) and carotenoides attracted so many attentions over the past three decades. Free radicals can lead to the development of cancer and cardiovascular disease (CVD) by lipid peroxidation and DNA damage. Basic studies suggested that antioxidants deactivate excited oxygen molecules and organic free radicals, and consequently reduce cardiovascular disease. Antioxidants can prevent the formation of atherosclerotic plaque by inhibiting oxidation of low-density lipoprotein cholesterol (LDL-C), decreasing thrombotic potential, platelet activity modifying, and vascular reactivity modifying. 4 , 5 Most of the people believe that if vitamins are not effective, at least they are safe. In spite of various researches in cellular biologic function of vitamins and interesting massages about their roles on health, the long term health consequences of vitamins consumption are unknown.

This study aimed to assess the side effects and possible harmful and detrimental properties of vitamins and to discuss whether vitamins can be used as safe health products or dietary supplements‏. We performed a MEDLINE/PubMed, EMBASE, Scopus and Google Scholar search and assessed reference lists of the included studies which were published from 1993 through 2015‏. The studies, with an emphasis on RCTs (randomized controlled clinical trials), were reviewed. As some vitamins such as fat-soluble vitamins (vitamin A, vitamin D, vitamin E), and also some of the water-soluble vitamins like folic acid may cause adverse events and some like vitamin C is widely taken assuming that it has so many benefits and no harm, we included relevant studies with negative or undesired results regarding the effect of these vitamins on health. We have also shown recommended dietary allowance (RDA)/adequate intake (AI) and tolerable upper intake level (UL) of these vitamins in Table 1 .

-
	15mg/d	1000mg/d
	Female: 75mg/d	2000mg/d
	Male: 90mg/d	-
	Female: 700µg/d	3000µg/d
	Male: 900µg/d	-
	400µg/d	1000µg/d
	18-50 years: 5µg/d	-
	50-70 years: 10µg/d	50µg/d
	>70 years:15µg/d	-

RDA: Recommended Dietary Allowance; AI: Adequate Intake; UL: Tolerable Upper Intake Level; data based on the National Academy of Sciences

Vitamin E (α-tocopherol)

Vitamin E is a lipid-soluble vitamin and a major component in the cell antioxidant defense system. It is exclusively obtained from the diet. 6 As it has been shown that vitamin E can reduce oxidative stress, its supplementation have been assessed as a therapy to prevent many chronic diseases in many clinical trials. However, several studies could not find significant effectiveness of vitamin E on prevention of cancer, 4 , 7 - 25 reduction in cardiovascular diseases, 8 , 13 , 25 - 36 and overall mortality reduction. 5 , 15 , 19 , 25 , 27 , 37 - 39 In a randomized, double-blind, placebo-controlled trial (The Physicians' Health Study II), a total of 14641 male physicians aging more than 50 years were enrolled. They received supplements of vitamin E (400 IU) every other day and were followed for 8 years. Compared to placebo, vitamin E did not have any effect on prostate cancer incidence (HR=0.97; 95% CI=0.85-1.09; P=0.58) or total cancer incidence (HR=1.04; 95% CI=0.95-1.13; P=0.41). These data provided no support for vitamin E supplementation to prevent cancer in men aging more than 50 years. 10 This finding was confirmed in another study. In a multicenter randomized trial, around 35000 healthy men prescribed vitamin E (400 IU/d) or placebo were followed up for 7-12 years. Data analysis showed that prostate cancer prevalence was higher among men in vitamin E group (HR=1.17; 99% CI=1.004-1.36, P=0.008). 4 , 16 A prospective cohort study assessed daily use of supplemental vitamin E in 77721 women and men aging 50-76 years for 10 years. Use of vitamin E supplement lead to a small increase in lung cancer risk (HR was 1.05 for every 100 mg increase in dose per day; 95% CI=1.00-1.09; P=0.033). This risk of supplemental vitamin E was mostly shown in current smokers (for every 100-mg per day increase, the HR was 1.11; 95% CI=1.03-1.19; P<0.01) and was at the greatest level for non-small cell type of lung cancer (HR=1.07 for every 100-mg/d increase; 95% CI=1.02-1.12; P=0.004). This increased risk was equivalent to a 7% rise for every 100 mg/day. So, there will be a 28% increased risk of lung cancer with taking 400 mg/day of vitamin E for ten years. 40

In 72829 nonsmoker Chinese female aging 40 to 70 years who were participating in Shanghai Women's Health Study (SWHS), the effect of tocopherol intake (from diet or supplements) and risk of lung cancer was assessed.

Total dietary tocopherol had an inverse association with risk of lung cancer in women receiving 14 mg/day (adequate intake of tocopherol) or more of tocopherol compared to those receiving less than this amount (HR=0.78; 95% CI=0.60–0.99). The protective effect of dietary tocopherol on risk of lung cancer was confined to women who were exposed to smoke (HR=0.53; CI=0.29–0.97; P=0.04). In contrast, use of vitamin E supplement was related with increased risk of lung cancer (HR=1.33; 95% CI=1.01–1.73), especially with risk of lung adenocarcinoma (HR=1.79‏; 95% CI=1.23–2.60). So, intake of dietary tocopherol may decrease lung cancer risk among non-smoker females; however, use of supplements may increase risk of lung adenocarcinoma. 41 Lonn et al in a randomized placebo-controlled trial showed that consumption of 400 IU/d vitamin E does not prevent cancer or cardiovascular disease and may even increase risk of heart failure in patients with diabetes mellitus or vascular disease. 8 Miller et al performed a meta-analysis on 19 clinical trials with 135967 participants and dosages of 16.5 to 2000 IU/d of vitamin E. They suggested that there is a dose-response relationship between vitamin E supplementation and all-cause mortality. The difference of all-cause mortality risk was 39 per 10,000 persons in high-dosage vitamin E trials (95% CI, 3 to 74 per 10,000 persons; P=0.035). The risk difference was -16 per 10,000 persons for low-dosage vitamin E trials (CI, -41 to 10 per 10,000 persons; P>0.2). A dose-response analysis revealed a statistically significant relationship between dosage of vitamin E and all-cause mortality, with increased risk of dosages >150 IU/d. A decreased risk of death was observed with lower doses of vitamin E (<400 IU) and an significant increased risk with high doses (≥400 IU). 38

Of course, there is an inconsistency among different studies which can be due to the effect of the different isoforms of vitamin E. The most common isoform which is used in vitamin E supplements is α-Tocopherol whereas β-tocopherol and γ-tocopherol are the isoforms which are available in large quantities in the diet and are more efficient in trapping reactive oxygen species and reactive nitrogen species. Experimental studies shows that α-tocopherol can induce apoptosis in lesser amounts. 41 One possible mechanism for the harmful effects of vitamin E observed in the studies is that, although vitamin E is thought to be an antioxidant, it might have prooxidant effects in some conditions as well. 40

In general, there is not any strong evidence in order to suggest vitamin E usage as a regular supplement for healthy people.

Vitamin C or L-ascorbic acid is an indispensable nutrient for humans. It performs numerous physiological functions like antioxidant activity, modulation of the immune system, and synthesis of collagen, carnitine and neurotransmitters. 42 - 44 Patients and physicians have expected to overcome chronic disease such as cardiovascular disease or cancer by consumption of vitamin C, based on its antioxidant activities. 45 Previous studies were not able to show any benefit regarding the consumption of vitamin C and cancer prevention, 9 , 12 , 15 , 23 - 25 mortality reduction, 5 , 10 , 12 , 15 , 18 , 19 , 25 , 37 , 46 prevention of cardiovascular events, 25 , 28 , 29 , 32 , 33 , 36 , 46 urinary stone production 47 and reduction of common cold incidence. 48 - 50 Lee et al assessed the association between intake of vitamin C and mortality from cardiovascular disease in 1923 diabetic postmenopausal women. They concluded that intake of vitamin C from food had no association with mortality outcomes. In contrast, supplemental vitamin C intake of greater than 300 mg/d showed a positive relationship with cardiovascular disease. 46 Effect of vitamin C in treatment and prevention of common cold is a very challenging topic and there have been lots of controversies since 70 years ago.

Results of a recent meta-analysis on 29 clinical trial including 11306 subjects showed that regular supplementation with vitamin C in the ordinary population did not have any effect on the incidence of common cold. In another study comparing 31 clinical trials with 9745 common cold episodes, duration of common cold symptoms modestly decreased with regular intake of vitamin C. A systematic review was performed on 598 participants who were exposed to short durations of excessive physical stress (including marathon runners and skiers). It revealed that Vitamin C halved the risk of common cold. The intervention of these studies was at least 0.2g/d orally administered vitamin C for a single day or for a period. 50

Although vitamin C is a vitamin with well-known and potent antioxidant capabilities, it has been shown that it can have prooxidant effects and can cause damage by stimulating lipid peroxidation. 46 In addition, short-term healthy effects of vitamin C may not be related to long-term beneficial effects and can even be harmful. One important point observed in some studies is that, vitamin C intake from food does not show the deleterious effects as seen with vitamin C intake from supplements. An explanation to this feature can be that the antioxidants which are naturally present in foods are biochemically balanced, which means that they are part of a combination of redox agents in oxidized and reduced forms‏, whereas this balance may be lacked in every supplement pill.

Vitamin A (Retinol) and beta-carotene

Vitamin A is one of the lipid-soluble vitamins that have antioxidant functions. It is provided by the diet in two forms: preformed vitamin A (which is naturally found just in animal products) and carotenoid vitamin A precursors (found primarily in foods of plant origin). Beta-carotene is the main precursor of vitamin A which also has anti-oxidant properties. Vitamin A is an essential agent for vision, embryogenesis, reproduction, the integrity of membrane structures, epithelial differentiation, growth, and development. 51 , 52 Epidemiologic studies have shown a reduced risk of various chronic diseases, particularly cancers of lung, gastrointestinal tract, bladder, breast and pancreas and cardiovascular disease with dietary consumption of various carotenoids. 53 - 61 However, randomized clinical trials have not shown any consistent reduction in the incidence of cancers or cancer deaths, or of cardiovascular disease. 7 , 62 - 66 Worse still, an elevated risk of lung cancer in high-risk individuals (asbestos workers and smokers) who were given high doses of beta-carotene alone or in combination with other antioxidants has been reported. 7 , 64 The Alpha-Tocopherol Beta-Carotene Cancer Prevention (ATBC) Trial and the Beta-Carotene and Retinol Efficacy Trial (CARET) were planned to assess beta-carotene effect on incidence of lung cancer. ATBC tested the combination of alpha-tocopherol (50 mg) and beta-carotene(20 mg) in 29133 male current cigarette smokers. 7 CARET compared the combination of retinyl palmitate (25000 IU) and beta-carotene (30 mg) with placebo in more than 18000 current and recent ex-smokers (male and female) and asbestos workers (male). 63 After 6.1 years of follow-up, ATBC showed a 16% increase in incidence of lung cancer and 8% increase in deaths from all causes in individuals receiving beta-carotene compared to placebo-receiving subjects. 7 , 66 After 4 years of follow-up, CARET showed a 28% increased incidence of lung cancer and 17% increase in all-cause mortality and greater mortality from cardiovascular disease in vitamin-receiving group than placebo group. 64 It is obvious from these two studies that beta-carotene containing supplements can have adverse effects such as increased incidence of lung cancer and greater mortality in cigarette smokers. Another concern about Vitamin A is its teratogenic effect. A study performed by Rothman et al on 22748 pregnant women showed that the prevalence of cranial-neural-crest tissue defects was 3.5 times in babies whose mothers consumed >15000 IU/d vitamin A from food and supplements compared to the babies whose mothers consumed ≤5000 IU/d (95% CI, 1.7 to 7.3). They concluded that high doses of vitamin A can be teratogenic and almost 1 in 57 infants whose mothers took >10000 IU/d of vitamin A supplements had a malformation. 52

Vitamin A intake in abundant amounts can have deleterious effects on bone via induction of osteoporosis. This can cause an increased fracture risk, especially in those with previous osteoporosis risk. Some studies have shown that intake of high amounts of vitamin A can lead to an elevated risk of fracture in hip. 67 , 68 A study showed that there is a 68%-increased risk of hip fracture for each 1-mg increase in daily intake of retinol (95% CI, 18% to 140%; P for trend, 0.006). For intake >1.5 mg/d compared with intake < 0.5 mg/d, bone mineral density was reduced by 10% at the femoral neck (P = 0.05), 14% at the lumbar spine (P = 0.001), and 6% for the total body (P = 0.009) and risk for hip fracture was doubled (odds ratio, 2.1 [CI, 1.1 to 4.0]). 67 In a prospective study involving 72337 postmenopausal women, women in the highest quintile of total vitamin A intake (>/=3000 µg/d of retinol equivalents [RE]) had a significantly elevated relative risk (RR) of hip fracture (RR, 1.48; 95% CI, 1.05-2.07; P for trend =.003) compared with women in the lowest quintile of intake (<1250 µg /d of RE). 68 In a prospective study of more than 2000 men, a 1.64-fold greater risk of any fracture (95% CI, 1.12 to 2.41) and 2.47-fold greater risk of hip fracture (95% CI, 1.15 to 5.28) was seen with serum retinol level in the highest quantile. 69

In the Iowa Women's Health Study, there was a greater risk of hip fracture in vitamin A users, but no apparent dose-response. They prospectively followed 34703 postmenopausal women for a duration of almost 9.5 years. It was shown that risk of hip fracture was 1.18 fold in vitamin A supplement users compared to nonusers (95% CI, 0.99 to 1.41), but there was not a greater risk of all fractures among the users of vitamin A supplement. 70

The importance of vitamin A in the bone remodeling process has been shown in various studies. Vitamin A deficiency results in retarded bone growth, but in the other hand hypervitaminosis A leads to accelerated bone resorption, bone fragility, and spontaneous fracture‏. Both osteoblasts and osteoclasts express the nuclear receptors for retinoic acid (retinoic acid receptors and retinoid X receptors). Retinoic acid inhibits osteoblast activity, stimulates osteoclast formation, and induces bone resorption. 51 , 67 ‏

Folate is a member of vitamin B family and a water-soluble vitamin. It is used for nucleotide biosynthesis, DNA replication, and methylation reactions in body. Folic acid is synthetic folate which is the form used in fortified foods and supplements. It is used alone or combined with other B vitamins in treatment or prevention of cardiovascular disease, macrocytic anemia and neural tube deficiency. 71 Experimental studies have shown that folate deficiency may initiate early stages of carcinogenesis, whilst high doses can enhance the growth of cancer cells. 72 , 73

In a study performed on 6837 patients suffering from ischemic heart disease, increased incidence of lung cancer (HR, 1.21; 95% CI, 1.03-1.41; P=0.02), cancer-related mortality (HR, 1.38; 95% CI, 1.07-1.79; P=0.01) and all-cause mortality (HR, 1.18; 95% CI, 1.04-1.33; P=0.01) was seen in subjects treated with 0.8 mg/d folic acid plus 0.4 mg/d vitamin B 12 . 74

Figueiredo et al showed increased risk of prostate cancer in men supplemented with 1 mg/d folic acid for 10 years (HR=2.63, 95% CI=1.23 to 5.65, P=0.01). 75

Zhang et al randomized 5442 women with cardiovascular disease and supplemented them with a mixture of folic acid, vitamin B 6 , and vitamin B 12 (2.5 mg, 50 mg and 1 mg, respectively) or placebo. They observed no effect of these agents on risk of total invasive cancer (HR=0.97; 95% CI=0.79-1.18; P=0.75) or breast cancer (HR=0.83; 95% CI=0.60-1.14; P=0.24). 76 Cole et al performed a clinical trial on almost 1000 men and women with a history of colorectal adenomas. They indicated that 1 mg/d folic acid for 6 years, does not decrease the colorectal adenoma formation risk (RR, 1.13; 95% CI, 0.93-1.37; P =0.23). In addition, a significant excess of prostate cancers was observed in the folate group (7.3% in the folic acid group versus 2.8% in the placebo group [P=0.01]). 77 Bazzanoet al performed a meta-analysis on 12 randomized controlled trials evaluating the effect of folic acid supplementation on risk of cardiovascular diseases. They found that supplementation with folic acid does not decrease the risk of cardiovascular events in patients with previous history of vascular disease. The overall relative risks (95% CI) of outcomes for patients treated with folic acid supplementation compared with controls were 0.95 (0.88-1.03) for cardiovascular diseases, 1.04 (0.92-1.17) for coronary heart disease, 0.86 (0.71-1.04) for stroke, and 0.96 (0.88-1.04) for all-cause mortality. 78 Albert et al in a randomized trial on 5442 women with CVD history showed that supplementation with folic acid and B vitamins for 7.3 years did not reduce cardiovascular events (P=0.65). 79 Graat et al performed a randomized control trial on 652 men taking physiological doses of multivitamins including 200µg/d of folic acid. They found that these agents had no effect on incidence of acute respiratory tract infections and their severity (P=0.58). 80

These findings highlight the potentially complex role of folate in carcinogenesis. Folate plays a dual role in carcinogenesis. When folate is administered to individuals with suboptimal folate status or in the early stages of carcinogenesis, it prevents tumor initiation; but when it is administered to individuals with high folate intake or in later stages of carcinogenesis (ie, once premalignant lesions are established), it promotes tumor development. 72

In most trials, the effects of calcium and vitamin D could not be separated because of their high correlation. Observational epidemiologic studies suggest that higher intake of calcium and vitamin D is associated with a decreased risk of colorectal cancer and polyp recurrence. 81 - 86 However, in a randomized controlled trial, daily supplementation of 36282 postmenopausal women with 1000 mg of elemental calcium and 400 IU of vitamin D3 for seven years did not have any effect on the incidence of colorectal cancer (HR, 1.08; 95% CI, 0.86 to 1.34; P=0.51). 87 Although the association between high calcium and vitamin D intake and high levels of 25-hydroxyvitamin D (25-OH D) with lower breast cancer risk has been reported in some observational studies, 88 - 90 findings of clinical trials do not support this relationship. In a study performed by Chlebowski et al on 36282 postmenopausal women receiving calcium and vitamin D3 (1000 mg/d and 400 IU/d, respectively) for almost 7.0 years, incidence of invasive breast cancer did not reduce with supplementation. Moreover, 25-OH D levels were not associated with further risk of breast cancer (HR, 0.96; 95% CI, 0.85 to 1.09). 91 The effect of vitamin D and calcium intake on bone density and risk of fracture remains equivocal and studies have shown mixed results. Michaëlsson et al assessed the relationship between dietary vitamin D and calcium intake with osteoporotic fracture risk. They used data from a population-based cohort study in 60689 Swedish women, aged 40-74 years and showed that intake of vitamin D was not related to risk of fracture. In addition, age-adjusted RR of all fractures was 1.02 for women in the highest quintiles compared to the women in the lowest quintiles of calcium and vitamin D intake (95% CI 0.88-1.17). They concluded that intake of calcium or vitamin D from diet did not seem to be important for osteoporotic fractures prevention in these women. 92 Nieves et al assessed the effect of vitamin D and calcium intake on bone density and risk of fracture in 76507 postmenopausal Caucasian women. They showed that higher intake of vitamin D and calcium could reduce the odds of osteoporosis (OR = 0.75; 95% CI, 0.68, 0.82 and OR = 0.73; 95% CI, 0.0.66, 0.81; respectively) but did not reduce the 3-year fracture risk in these women. 93

In the studies mentioned above, a significant relationship between vitamin D intake and risk of cancer or fracture is not observed. The most attractive explanation for these results might be that higher intakes of vitamin D are required for fracture or cancer prevention. 91 - 93

In recent decade, use of nutritional supplements has rapidly increased. One third of adults and half of population aging more than 55 years report taking of at least one supplement per day. In the present review, we evaluated the long term effects of some vitamins consumption on prevention or treatment of some chronic disease and the adverse effects of these supplements.

As vitamin A, E, D, C and folic acid are shown to have some deleterious effects in various studies, we focused on them in this narrative review. Results from related literature, summarized in Table 2 , showed that daily consumption of these vitamins in some cases not only had no benefit but also increased the risk of disease. With concern to results of these studies, there is a main question; should we quit taking these vitamins or should we use them wisely and just with physician order or pharmacists consults?


Klein EA et al (4)	35533 men	Selenium (200 μg/day)Vitamin E (400 IU/day)	7-12	Increased risk of prostate cancer
Heinonen OP et al (7)	29,133 male smokers	Alpha-tocopherol (50 mg /day), beta carotene (20 mg/day)	5-8	No reduction in the incidence of lung cancer
Lonn E et al (8)	9541patients with vascular disease or diabetes mellitus	Daily dose of natural source vitamin E (400 IU)	7	Increase the risk of heart failure
Coulter ID et al (9)	357 articles	Vitamin C(120-180mg/day) and E(400 -600 IU/day)	-	No prevention and/or treatment of cancer
Gaziano J et al(10)	14641 male with a history of prior cancer	Vitamin E(400 IU/day) and vitamin C (500 mg /day)	8	No reduction in risk of prostate and total cancer
Hunter DJ et al (11)	89494 women	Vitamins C, E ( ≥ 23,000 IU per day), and A(10,000 IU/day)	8	No influence on incidence of breast cancer
Kirsh VA et al (12)	29361 men	Vitamin E(>400 IU/day), beta-carotene(2000 microg/day), and vitamin C	8	No prevention on incidence of prostate cancer
the Women's Health Study ,Lee IM et al(13)	39876 healthy women	Vitamin E (600 IU)	10.1	No effect on cardiovascular events, cancer and total mortality
Liede K et al(14)	409 white male cigarette smokers,	Alpha-tocopherol (50 mg/day), beta-carotene (20 mg/ day)	5-7	No effect on preventing oral mucosal changes in smokers
Lin J et al (15)	8171 women at high risk for CVD	Vitamins C (500 mg/day) and E (600 IU/day) and beta carotene (50 /day)	4-8	No benefits in prevention of cancer
Lippman SM et al (16)	35533 men	Selenium (200 microg/day) and vitamin E(400 IU/day)	5.46	No prevention of prostate cancer
Wright MEet al(17)	29133 male smokers, free of cancer	Alpha-tocopherol (50 mg /day), beta carotene (20 mg/day)	-	No protective effect on upper aerodigestive tract cancers
Huang HY et al (18)	3710 potentially eligible articles	Multivitamin and mineral supplement(daily)	-	No benefits in preventing cancer and chronic disease
Hercberg S et al (19)	13017 adults	combination of 120 mg of ascorbic acid, 30 mg of vitamin E, 6 mg of beta carotene, 100 mug of selenium, and 20 mg of zinc	7.5	low total cancer incidence and all-cause mortality in men but not in women
Cook NR et al (20)	22071 male physicians	Beta-carotene (50 mg)	13	No overall effect on total cancer
Wright ME et al (21)	295344 cancer-free men	Vitamin E	5	No protection against prostate cancer
Greenberg ER et al (22)	864 colorectal adenoma patients	Beta carton(25 mg daily) , vitamin C (1 g daily) and vitamin E (400 mg daily)	4	No prevention of colorectal cancer
Larsson SCet al(23)	35329 cancer-free women	Multivitamins	9.5	Increased risk of breast cancer
Lawson KA et al (24)	295344 cancer-free men	Multivitamins	5	Increased risk of advanced and fatal prostate cancers
Neuhouser ML et al (25)	182099 participants	Multivitamin (daily)	8	No influence on cancer and CVD
Yusuf Set al(26)	2545 women and 6996 men	400 IU of vitamin E daily	4.5	No effect on cardiovascular outcomes
Vivekananthan DP et al(27)	81788 patients in vitamin E trials and 138113 in beta carotene trials	Vitamin E 50-800 IU, and beta carotene 15-50 mg	1.4 to 12.0	No benefit of vitamin E in mortality/ increase in mortality with beta carotene
Sesso HD et al (28)	14641 male physicians	Vitamin E (400 IU /day and vitamin C (500 mg/day)	8	No reduction in risk of major cardiovascular events
Salonen RM et al(29)	520 smoking and nonsmoking men and postmenopausal women	136 IU of vitaminE plus 250 mg of slow-release vitaminC twice daily	6	slowing down atherosclerotic progression
Rapola JM et al (30)	1795 male smokers who had angina pectoris	Alpha tocopherol ( 50 mg/day) and beta carotene (20 mg/day)	4	No beneficial effect on angina pectoris
Rapola JM et al (31)	29133 male smokers	50 mg/d of alpha tocopherol, 20 mg/d of betacarotene	4.7	No beneficial effect on angina pectoris
Kushi LH et al(32)	34486 postmenopausal women	Vitamins A, E, and C	7	No effect on mortality from coronary disease
Cook NR et al (33)	8171 female health professionals	Ascorbic acid (500 mg/d), vitamin E (600 IU every other day), and beta carotene (50 mg every other day)	2-3	No effect on cardiovascular events
Ascherio A et al(34)	43738 men	Vitamin E (411 IU/d), C (1167 mg/d)	8	No reduction in risk of stroke
Waters DD et al (35)	423 postmenopausal women	400 IU of vitamin E plus 500 mg of vitamin C twice daily	-	No cardiovascular benefit
Bleys J et al(36)	2311 articles	Antioxidants (vitamins E and C, beta-carotene, or selenium) and trials using B vitamins (folate, vitamin B-6, or vitamin B-12)	0.3 and 7.2	No evidence of a protective effect on the progression of atherosclerosis
Pocobelli G et al (37)	77673persons	Multivitamins, vitamin C, and vitamin E(dose depend on BMI	10	Not associated with cancer mortality
Miller ER 3rd et al (38)	135967 participants in 19 clinical trials	Vitamin E (150-400 IU/d)	-	High doses increase death risk
Hayden KM et al (39)	A defined population aged 65 years or older	VitaminE	-	unrelated to mortality, even increased mortality in severe CVD
Slatore CG et al (40)	77721 men and women	Multivitamins, vitaminC, vitaminE, and folate	10	Not associated with decreased risk of lung cancer
Wu QJ et al (41)	72,829 nonsmoker female	Vitamin E	12.02	increased risk of lung adenocarcinom
Lee DH et al (46)	1923 postmenopausal women with diabetes	Vitamin C	-	Increased risk of CVD mortality
Traxer O et al (47)	12 normal subjects and 12 CaOxstone formers	2 g ascorbic acid daily	2, 6-day phases	No change in urinary pH but an increase in urinary oxalate
Douglas RM et al (48)	29 trial comparisons involving 11077 study participants	Vitamin C (0.2 g per day or more)	-	Failure n reduction of common colds
Douglas RM et al (49)	30 trial comparisons involving 11350 study participants	Vitamin C (0.2 g per day or more)	-	Failure in reduction of common colds
Hemilä Het al(50)	29 trial comparisons involving 11306 participant	Vitamin C (0.2 g per day or more)	-	Failure in reduction of common colds
HennekensCH et al(62)	22071 male	Supplementation with beta carotene (50 mg on alternate days)	-	Neither benefit nor harm in malignant neoplasms
Omenn GS et al (64)	18314 smokers, and workers exposed to asbestos	Beta carotene (30 mg) and vitamin A(25,000 IU)	2	No benefit on lung cancer
van Zandwijk Net al(65)	2592 patients	Vitamin A (300000 IU daily for 1 year followed by 150000 IU for a 2 year), N-acetylcysteine (600 mg daily)	2	No benefit for patients with head and neck cancer or with lung cancer
Albanes D et al (66)	29133 smoker men	Alpha-tocopherol (50 mg), beta-carotene (20 mg)	5-8	increased lung cancer incidence in cigarette smokers
Melhus H et al(67)	175 women for the cross-sectional study, 247 women for the nested case-control study	Retinol	-	Increased osteoporosis
Feskanich D et al(68)	72 337 postmenopausal women	Vitamin A	18	development of osteoporotic hip fractures
Michaëlsson K et al (69)	2322 men	Retinol	30	1.6-fold increased risk of any fracture and 2.5-fold increased risk of hip fracture
Lim LSet al(70)	34703 postmenopausal women	Vitamin A	9.5	1.18-fold increased risk of hip fracture
Ebbing M et al (74)	6837 patients with ischemic heart disease	Folic acid (0.8 mg/d) and vitamin B (0.4 mg/d), vitamin B (40 mg/d)	9	Increased cancer risk
Figueiredo JC et al (75)	643 men	1 mg of folic acid	10.8	Increased risk of prostate cancer
Zhang SM et al (76)	5442 female health professionals	Combination of folicacid, vitamin B6, and vitamin B12	7.3	No effect on overall risk of total invasive cancer or breast cancer
Cole BF et al(77)	1021 men and women with a recent history of colorectal adenomas	1 mg/d of folic acid	3	No reduction in colorectal adenoma risk
Bazzano LAet al(78)	16958 participants with preexisting vascular disease	Folic acid(0.5-15mg/day)	-	No reduction in cardiovascular diseases or all-cause mortality
Albert CM et al (79)	5442 women	Combination of folicacid, vitamin B6, and vitamin B12	7.3	No reduction in cardiovascular events
Graat JM et al (80)	652 non-institutionalized individuals	Physiological doses of multivitamin-minerals, 200 mg of vitaminE	1.3	No effect on incidence and severity of respiratory tract infections
Wactawski-Wende Jet al(87)	36282 postmenopausal women	1000 mg of elemental calcium and 400 IU of vitamin D3	7	No effect on the incidence of colorectal cancer
Chlebowski RTet al(91)	36282 postmenopausal women	1000 mg of elemental calcium with 400 IU of vitamin D(3)	7	No reduction in invasive breast cancer incidence
Michaëlsson K et al (92)	60689 women	Calcium and vitamin D	-	No prevention of osteoporotic fractures
Nieves JW et al (93)	76507 postmenopausal women	calcium and vitamin D	-	Reduction in the odds of osteoporosis but not the 3-year risk of fracture

It was implied that adverse effects of some vitamins such as vitamin E may be dose related. Due to the unlimited access of people to vitamins and also lack of patient's attention into multivitamins ingredients and their doses, it may be high probable that a patient use vitamins in higher doses. It can be suggested that vitamin administration should be under the control of health provider professionals like pharmacists and only be marketed by pharmacies in order to provide critical information for patients about appropriate vitamins use. In addition, labeling of vitamins should include information on recommended upper intake, safe dosing and possible toxicities.

In conclusion, taking supplements of vitamin E, A, C, D, and folic acid for prevention of disease or cancer is not always effective, and can even be harmful to the health. So, it would be rational to limit these supplements consumption to those having deficiencies of the mentioned vitamins.

Ethical Issues

Not applicable.

Conflict of Interest

The Authors report no declaration of interest.

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Vitamin Essay Examples

Vitamin c and its benefits for skin.

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The Link Between Vitamin a Deficiency and Diabetes Mellitus

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Vitamin E and Coronary Heart Disease

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Vitamins: Definition and Main Advantages

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Vitamin D Deficiency and Risk of Mental Conditions

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The Benefits and Harms of Uv Exposure for Vitamin D Formation

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The Utilization of Red Seed Guava and Rosella Flower as Source of Vitamin C

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The Effects of Vitamin D on Type One Diabetes

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The Relationship Between Vitamin D Intake and Cognitive Decline

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Vitamin D: Old Roles and New Discoveries

Vitamin D is a fat-soluble vitamin that has various forms. It regulates bone protein formation and stimulates calcium absorption. There is a crucial receptor that helps vitamin D perform its functions and is termedvitamin D receptor (VDR) that has the chemical formula '1,25(OH)2D'. Vitamin D...

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