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Vitamins are organic components in food that are needed in very small amounts for growth and for maintaining good health. The vitamins include vitamin D, vitamin E, vitamin A, and vitamin K, or the fat-soluble vitamins, and folate (folic acid), vitamin B12, biotin, vitamin B6, niacin, thiamin, riboflavin, pantothenic acid, and vitamin C (ascorbic acid), or the water-soluble vitamins. Vitamins are required in the diet in only tiny amounts, in contrast to the energy components of the diet. The energy components of the diet are sugars, starches, fats, and oils, and these occur in relatively large amounts in the diet.
Most of the vitamins are closely associated with a corresponding vitamin deficiency disease. Vitamin D deficiency leads to diseases of the bones such as osteoporosis and rickets. Vitamin E deficiency occurs only rarely, and causes nerve damage. Vitamin A deficiency is common throughout the poorer parts of the world, and causes night blindness. Severe vitamin A deficiency can result in xerophthalamia, a disease which, if left untreated, results in total blindness. Vitamin K deficiency results in spontaneous bleeding. Mild or moderate folate deficiency is common throughout the world, and can result from the failure to eat green, leafy vegetables or fruits and fruit juices. Folate deficiency causes megaloblastic anemia, which is characterized by the presence of large abnormal cells called megaloblasts in the circulating blood. The symptoms of megaloblastic anemia are tiredness and weakness. Vitamin B12 deficiency occurs with the failure to consume meat, milk or other dairy products. Vitamin B12 deficiency causes megaloblastic anemia and, if severe enough, can result in irreversible nerve damage. Niacin deficiency results in pellagra. Pellagra involves skin rashes and scabs, diarrhea, and mental depression. Thiamin deficiency results in beriberi, a disease that can cause atrophy, weakness of the legs, nerve damage, and heart failure. Vitamin C deficiency results in scurvy, a disease that involves bleeding. Specific diseases uniquely associated with deficiencies in vitamin B6, riboflavin, or pantothenic acid have not been found in humans, though persons who have been starving, or consuming poor diets for several months, might be expected to be deficient in most of the nutrients, including vitamin B6, riboflavin, and pantothenic acid.
Some of the vitamins serve only one function in the body, while other vitamins serve a variety of unrelated functions. Therefore, some vitamin deficiencies tend to result in one type of defect, while other deficiencies result in a variety of problems.


People are treated with vitamins for three reasons. The primary reason is to relieve a vitamin deficiency, when one has been detected. Chemical tests suitable for the detection of all vitamin deficiencies are available. The diagnosis of vitamin deficiency often is aided by visual tests, such as the examination of blood cells with a microscope, the x-ray examination of bones, or a visual examination of the eyes or skin.
Essential Vitamins
Vitamin What It Does For The Body
Vitamin A (Beta Carotene) Promotes growth and repair of body tissues; reduces susceptibility to infections; aids in bone and teeth formation; maintains smooth skin
Vitamin B-1 (Thiamin) Promotes growth and muscle tone; aids in the proper functioning of the muscles, heart, and nervous system; assists in digestion of carbohydrates
Vitamin B-2 (Riboflavin) Maintains good vision and healthy skin, hair, and nails; assists in formation of antibodies and red blood cells; aids in carbohydrate, fat, and protein metabolism
Vitamin B-3 (Niacinamide) Reduces cholesterol levels in the blood; maintains healthy skin, tongue, and digestive system; improves blood circulation; increases energy
Vitamin B-5 Fortifies white blood cells; helps the body's resistance to stress; builds cells
Vitamin B-6 (Pyridoxine) Aids in the synthesis and breakdown of amino acids and the metabolism of fats and carbohydrates; supports the central nervous system; maintains healthy skin
Vitamin B-12 (Cobalamin) Promotes growth in children; prevents anemia by regenerating red blood cells; aids in the metabolism of carbohydrates, fats, and proteins; maintains healthy nervous system
Biotin Aids in the metabolism of proteins and fats; promotes healthy skin
Choline Folic Acid (Folate, Folacin) Helps the liver eliminate toxins Promotes the growth and reproduction of body cells; aids in the formation of red blood cells and bone marrow
Vitamin C (Ascorbic Acid) One of the major antioxidants; essential for healthy teeth, gums, and bones; helps to heal wounds, fractures, and scar tissue; builds resistance to infections; assists in the prevention and treatment of the common cold; prevents scurvy
Vitamin D Improves the absorption of calcium and phosphorous (essential in the formation of healthy bones and teeth) maintains nervous system
Vitamin E A major antioxidant; supplies oxygen to blood; provides nourishment to cells; prevents blood clots; slows cellular aging
Vitamin K (Menadione) Prevents internal bleeding; reduces heavy menstrual flow
A second reason for vitamin treatment is to prevent the development of an expected deficiency. Here, vitamins are administered even with no test for possible deficiency. One example is vitamin K treatment of newborn infants to prevent bleeding. Food supplementation is another form of vitamin treatment. The vitamin D added to foods serves the purpose of preventing the deficiency from occurring in persons who may not be exposed much to sunlight and who fail to consume foods that are fortified with vitamin D, such as milk. Niacin supplementation prevents pellagra, a disease that occurs in people who rely heavily on corn as the main source of food, and who do not eat much meat or milk. In general, the American food supply is fortified with niacin.
A third reason for vitamin treatment is to reduce the risk for diseases that may occur even when vitamin deficiency cannot be detected by chemical tests. One example is folate deficiency. The risk for cardiovascular disease can be slightly reduced for a large fraction of the population by folic acid supplements. And the risk for certain birth defects can be sharply reduced if certain pregnant women use folic acid supplements.
Vitamin treatment is important during specific diseases where the body's normal processing of a vitamin is impaired. In these cases, high doses of the needed vitamin can force the body to process or utilize it in the normal manner. One example is pernicious anemia, a disease that tends to occur in middle age or old age, and impairs the absorption of vitamin B12. Surveys have revealed that about 0.1% of the general population, and 2-3% of the elderly, may have the disease. If left untreated, pernicous anemia leads to nervous system damage. The disease can easily be treated with large oral daily doses of vitamin B12 (hydroxocobalamin) or with monthly injections of the vitamin.
Vitamin supplements are widely available as over-the-counter products. But whether they work to prevent or curtail certain illnesses, particularly in people with a balanced diet, is a matter of debate and ongoing research. For example, vitamin C is not proven to prevent the common cold. Yet, millions of people take it for that reason. A physician or pharmacist can provide more information on the appropriate use of multivitamin supplements. Likewise, though vitamin supplements have been touted as a prevention for cancer, a 2004 report by the U.S. Preventive Services Task Force concluded that the evidence is inadequate to recommend supplementation of vitamins A, C, or E, multivitamins with folic acid, or antioxidant combinations to decrease the risk of cancer.


Vitamin A and vitamin D can be toxic in high doses. Side effects range from dizziness to kidney failure. A physician or pharmacist can help with the correct use of a multivitamin supplement that contains these vitamins.


Vitamin treatment usually is done in three ways: by replacing a poor diet with one that supplies the recommended dietary allowance, by consuming oral supplements, or by injections. Injections are useful for people with diseases that prevent absorption of fat-soluble vitamins. Oral vitamin supplements are especially useful for people who otherwise cannot or will not consume food that is a good vitamin source, such as meat, milk, or other dairy products. For example, a vegetarian who will not consume meat may be encouraged to consume oral supplements of vitamin B12.
Treatment of genetic diseases that impair the absorption or utilization of specific vitamins may require megadoses of the vitamin throughout one's lifetime. Megadose means a level of about 10-1,000 times greater than the recommended daily allowance (RDA). Pernicious anemia, homocystinuria, and biotinidase deficiency are three examples of genetic diseases that are treated with megadoses of vitamins.


The diagnosis of a vitamin deficiency usually involves a blood test. An overnight fast usually is recommended as preparation prior to withdrawal of the blood test so that vitamin-fortified foods do not affect the test results.


Response to vitamin treatment can be monitored by chemical tests, by an examination of red blood cells or white blood cells, or by physiological tests, depending on the exact vitamin deficiency.


Few risks are associated with supervised vitamin treatment. Risks depend on the vitamin and the reason why it was prescribed. Ask a physician or pharmacist about how and when to take vitamin supplements, particularly those that have not been prescribed by a physician.



"The Next Big Deficiency." Chain Drug Review February 16, 2004: 26.
Sadovsky, Richard. "Can Vitamins Prevent Cancer and Heart Disease?" American Family Physician February 1, 2004: 631.

Key terms

Genetic disease — A genetic disease is a disease that is passed from one generation to the next, but does not necessarily appear in each generation. An example of genetic disease is Down's syndrome.
Plasma — Blood consists of red and white cells, as well as other components, that float in a liquid. This liquid is called plasma.
Recommended dietary allowance (RDA) — The Recommended Dietary Allowances (RDAs) are quantities of nutrients of the diet that are required to maintain human health. RDAs are established by the Food and Nutrition Board of the National Academy of Sciences and may be revised every few years. A separate RDA value exists for each nutrient. The RDA values refer to the amount of nutrient expected to maintain health in the greatest number of people.
Serum — Serum is blood plasma with the blood clotting proteins removed. Serum is prepared by removing blood from the subject, allowing the blood naturally to form a blood clot, and then using a centrifuge to remove the red blood cells and the blood clot. The blood clot takes the form of an indistinct clump.
Vitamin status — Vitamin status refers to the state of vitamin sufficiency or deficiency of any person. For example, a test may reveal that a patient's folate status is sufficient, borderline, or severely inadequate.


Chemical compounds necessary for normal body function. Vitamins are needed for the proper synthesis of body building material, HORMONES and other chemical regulators; for the biochemical processes involved in energy production and nerve and muscle function; and for the breakdown of waste products and toxic substances. The B group of vitamins are COENZYMES without which many body ENZYMES cannot function normally. The amounts of vitamins needed for health are very small and are almost always present in adequate amounts in normal, well-balanced diets. Excess intake of vitamins A and D is dangerous. Vitamins C and E are antioxidants and may be valuable, in doses many times the minimum requirement, in combatting the damaging effect of FREE RADICALS. Folic acid supplements are valuable in preventing NEURAL TUBE DEFECTS. Vitamins are conventionally divided into the fat-soluble group A, D, E and K, and the water-soluble group, vitamin C (ascorbic acid) and the B vitamins-B1 (thiamine), B2 (riboflavine, riboflavin), nicotinic acid, B6 (pyridoxine), pantothenic acid, biotin, folic acid and B12. The term was derived from the belief that vitamins were ‘vital amines’.


organic substances that are necessary in the diet, in very small quantities, for normal growth and health: the recommended daily allowance (RDA) for any vitamin, widely quoted on food and drink labels, is less than 200 mg. Originally identified by alleviation of conditions caused by their deficiency (e.g. of scurvy in ships' crews in the 1750s by providing citrus fruit, the vital component being found later to be ascorbic acid, vitamin C). Nowadays hypovitaminosis due to lack of one or more vitamins is rare on a well-balanced diet, although occasionally an athlete may suffer from a deficiency, e.g. if dieting for weight loss or eliminating particular foods or food groups from the diet. hypervitaminosis can occur with excessive intake of one or more vitamins. The International Olympic Committee states that no vitamin supplements should be required if the diet is well balanced but athletes do often take them, especially vitamins C, B-complex and E, with a possible danger to their health by overconsumption. For sources, functions and deficiency effects, see Table 1.
Table 1: Micronutrients: vitamins
VitaminRNI (DoH 1991)SourcesAction/functionsDeficiencyExcessSpecial points
Water soluble
Vitamin B group
B1 Thiamin(e)0.4 mg/1000 kcalFortified breakfast cereals, yeast extract, vegetables, fruit, wholegrain cereals, milk, liver, eggs, porkCoenzyme for carbohydrate metabolismEncephalopathy can occur with alcohol excess and low food intake. Beri-beri where polished rice is stapleHeadache, insomnia, irritability, contact dermatitisRequirement related to carbohydrate intake
B2 Riboflavin
  • Female 1.1 mg/d
  • Male 1.3 mg/d
Milk, milk products, offal, yeast extract, fortified breakfast cerealsCoenzyme for the metabolism of carbohydrate, fat and proteinFissures at corners of mouth; tongue inflammation; corneal vascularizationNo toxic effects, since large quantities are not absorbedDestroyed by sunlight
B3 Niacin (nicotinic acid and nicotinamide)6.6 mg/1000 kcal as nicotinic acid equivalentsMeat, fish, yeast extract, pulses, wholegrains, fortified breakfast cerealsEnergy metabolism, as part of coenzymes NAD and NADP involved in oxidation and reduction reactionsPellagra: dermatitis, diarrhoea and dementiaLiver damage, skin irritationAlso synthesized from the amino acid tryptophan
B5 Pantothenic acidNone setWidespread in food, e.g. liver, eggs, yeast, vegetables, pulses, cerealsProtein, fat, carbohydrate and alcohol metabolismVomiting, insomniaNot reported
B6 Pyridoxine
  • Female 1.2 mg/d
  • Male 1.4 mg/d
Meat, fish, eggs, some vegetables, wholegrainsProduction of haemoglobin and of coenzymes involved in many metabolic processesRare. Metabolic and nervous system disordersPeripheral nerve damageRequirement is related to protein intake
BiotinNone setWidely distributed in many foods, e.g. offal, egg yolk, legumes, etc. Can be synthesized by intestinal bacteriaEssential in fat metabolismRare; dermatitis, hair loss, nausea, fatigue and anorexiaNone known
B12 Cobalamins15 μg/g of proteinAnimal products, meat, eggs, fish, dairy products, yeast extract
  • Essential for red blood cell formation and nerve myelination.
  • Needed for use of folate
Anaemia; irreversible spinal cord damageNot reported
  • Absorption requires 'intrinsic factor' produced by the stomach.
  • Only in foods of animal origin, so strict vegetarians and vegans require supplements
Folates (folic acid)200 μg/dGreen leaf vegetables, bread, fortified breakfast cereals, yeast extract, liverRed blood cell production; DNA synthesis
  • Anaemia; growth retardation. May contribute to Alzheimer's.
  • Fetal defects
Can mask the effects of B12 deficiencySupplements before and during pregnancy reduce the incidence of spinal cord defects
Vitamin C ascorbic acid40 mg/d
  • Citrus fruits, kiwi fruit, blackcurrants, strawberries; green peppers, green leaf vegetables, potatoes, tomatoes.
  • Content decreases with storage
Collagen synthesis, formation of bones, connective tissue, teeth. Iron absorption for red blood cell production. Acts as an antioxidantSore mouth and gums; capillary bleeding; scurvy; delayed wound healing, scar break downDiarrhoea; oxalate stones in kidneysDestroyed by cooking in the presence of air and by plant enzymes released when cutting and grating raw food
Fat soluble
Vitamin A retinol
  • Female 600 μg/d
  • Male 700 μg/d
As retinol in liver, kidney, oily fish, egg yolk, full-fat dairy produce. As the provitamin carotenes in green, yellow, orange and red fruit and vegetables, e.g. broccoli, carrots, apricots, mangoes, sweet potatoes and tomatoesVisual pigments in retina, aids night vision. Normal growth and development of tissues; essential for healthy skin and mucosae. Acts as an antioxidantPoor growth; rough dry skin and mucosae; xerophthalmia and eventual blindness; increased risk of infection; poor night visionIn pregnancy, high doses can cause fetal malformationsSynthesized in the body from carotenes present in the diet
Vitamin D cholecalciferol ergosterol10 μg/d if houseboundOily fish, egg yolk, butter, fortified margarine; action of ultraviolet rays (sunlight)Calcium and phosphorus homeostasisRickets (children); osteomalacia (adults)Rare; weight loss and diarrhoeaProduced in the body by action of sunlight on a provitamin in the skin: deficiency develops in those who are not exposed to sun
Vitamin E tocopherols tocotrienesNone setWheat germ, vegetable oils, nuts, seeds, egg yolk, cereals, dark green vegetables
  • Antioxidant.
  • Protects against cell membrane damage
Neurological abnormalities; anaemia: rare, from malnutrition or malabsorptionMuscle weakness, gastrointestinal disordersRequirement is increased with increased intake of polyunsaturated fatty acids
Vitamin K phylloquinones menaquinonesNone setGreen leafy vegetables, fruit and dairy productsNeeded for the production of prothrombin and other coagulation factorsImpaired clotting; liver damageNot so far observed from naturally occurring vitaminSynthesized by intestinal bacteria so deficiency unusual

Patient discussion about vitamins

Q. Should I take vitamins? I try to eat a healthy balanced diet everyday. Do I still need to take vitamins additionally?

A. Unless your Doctor told you that you suffer from a vitamin deficiency, then eating a healthy balanced diet is enough in order to get all the necessary vitamins. Make sure to eat fresh fruits and vegetables, which are rich with them. Also People who eat a vegetarian diet may need to take a vitamin B12 supplement.

Q. Are Vitamins really helpful? I realize that there's an entire industry around it but I was wondering how helpful vitamins really are. Is there a difference between vitamins from fruits and vegetables and vitamins that you buy off the shelve? Is there such a thing as taking too much vitamins?

A. Yes, vitamins are helpful. I recently stopped taking my supplement to see if I felt a difference. Once I stopped taking it my anxiety attacks returned and my energy level went down. Nutrition that we get from food is the best, but the truth is that we don't get the amount of nutrition that we need daily. Yes, it is a such thing as taking too many vitamins. This is why it is still good consult with your doctor when taking any kind of vitamin or supplement. When chosing a vitamin for myself price is not a concern when it comes to health. This is why I prefer more expensive vitamins rather than over the counter.

Q. what vitamins are recommended for treating cold? and what is the right amount of it ?

A. Actually, although studied in trials, vitamins C, E and zinc wasn't found to have a substantial effect either preventing or relieving the symptoms of common cold, so currently these vitamins can't be recommended for the treatment of common cold.

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More discussions about vitamins
References in periodicals archive ?
Vitamin E supplements are fairly popular in the US.
Various forms of vitamin D: We know about 5 forms of vitamin D, of which vitamins D2 and D3 are the major forms as far as humans are concerned.
Canadian researchers gave more than 5,500 people with heart disease or diabetes either a daily placebo or a combination of folic acid (2,500 mcg), vitamin B-6 (50 mg), and vitamin B-12 (1,000 mcg) as part of the Heart Outcomes Prevention Evaluation (HOPE-2) trial.
The last time I looked, the recommended daily allowance (RDA) for vitamin E was only 30 international units, but typical supplement pills had 200 or 400 international units.
Time release is not that useful for vitamins,'' Gean says.
The closer you can stay to fresh, the greater the vitamin and mineral content that remains intact.
The scientific literature tells us that vitamin D is needed not only for healthy bones and optimal growth and development, but also to prevent colon cancer, MS, and reproductive problems.
The cost of providing vitamin D supplementation of 1,000 IU (International Units) per day for an individual is probably less than $2 per month, and providing adequate exposure to UVB radiation each day might cost even less.
The best solution is to choose a low cost, generic daily multivitamin that provides 100%, but not more, of each vitamin.
This citrus-flavored carbonated beverage contains 250% vitamin B6, 100% vitamins C, BI 2, riboflavin, and niacin, 50 mg Siberian ginseng and guarana, and 100 mg bee pollen and taurine.
Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc.