Vitamins

Vision Health A step-by-step "how-to" instruction.

More about Vitamins: Purpose Precautions Preparation Aftercare Risks Resources

Definition

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 causes rickets, a disease of the bones. Vitamin E deficiency occurs only very 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 resulting in 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 the 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. Hence, some vitamin deficiencies tend to result in one type of defect, while other deficiencies result in a variety of problems.

Description

Vitamin treatment is usually 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 persons with diseases that prevent absorption of fat-soluble vitamins. Oral vitamin supplements are especially useful for persons 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 which 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 RDA. Pernicious anemia, homocystinuria, and biotinidase deficiency are three examples of genetic diseases which are treated with megadoses of vitamins.

— Tom Brody, PhD

Dictionary: vi·ta·min  (vī'tə-mĭn)

Any of various fat-soluble or water-soluble organic substances essential in minute amounts for normal growth and activity of the body and obtained naturally from plant and animal foods.

[Alteration of vitamine : Latin vīta, life + AMINE (so called because they were originally thought to be amines).]

Key Terms: Antioxidant, Cancer, Free radicals, Malignant.

Definition

Vitamins are compounds that are essential in small amounts for proper body function and growth. Vitamins are either fat soluble: A, D, E, and K; or water soluble: vitamin B and C. The B vitamins include vitamins B₁(thiamine), B₂ (riboflavin), and B₆ (pyridoxine), pantothenic acid, niacin, biotin, folic acid (folate), and vitamin B₁₂ (cobalamin). Vitamins also may be referred to as micronutrients.

Description

A guide to the amount an average person needs each day to remain healthy has been determined for each vitamin. In the United States, this guide is called the recommended daily allowance (RDA). Consuming too little of certain vitamins may lead to a nutrient deficiency. Consuming too much of certain vitamins may lead to nutrient toxicity.

Consumption of a wide variety of foods that have adequate vitamins and minerals is the basis of a healthy diet. Good nutrition may assist in the prevention of cancer or may help cancer patients to feel better and fight infection during treatments. Obtaining nutrients through food remains the best method for obtaining vitamins, however, requirements may be higher because of the tumor or cancer therapy. Therefore, supplements may be necessary.

The following vitamins are important in a healthy diet and also may assist in cancer prevention. Their role in maintaining health and the best food sources are listed below.

Vitamin A (retinal, carotene)

• role in growth and repair of body tissues
• important in night vision
• immune function
• Best sources: eggs, dark green and yellow fruits and vegetables, low-fat dairy products, liver

Vitamin B6 (pyridoxine)

• role in formation of antibodies
• important in carbohydrate and protein metabolism
• red blood cells
• nerve function
• Best sources: lean meat, fish, poultry, whole grains, and potatoes

Folic acid (folate)

• assists in red blood cell formation
• important in protein metabolism
• growth and cell division
• Best sources: green leafy vegetables, poultry, dried beans, fortified cereals, nuts, and oranges

Vitamin C (ascorbic acid)

• resistance to infection
• important in collagen maintenance
• contributes to wound healing
• strengthens blood vessels
• assists in maintaining healthy gums
• Best sources: citrus fruits, tomatoes, melons, broccoli, green and red peppers, and berries

Vitamin E (tocopherol)

• may assist in immune function
• important in preventing oxidation of red blood cells and cell membranes
• Best sources: vegetable oils, wheat germ, nuts, dark green vegetables, beans, and whole grains

Purpose

Specific nutrients have been linked to prevention of several cancers of the colon, breast, prostate, stomach, and other types of tumors. A high intake of fruits and vegetables as well as fiber appears particularly protective, while a diet high in fat has been implicated as a cancer risk.

Vitamins Important for Cancer Prevention

Antioxidant vitamins are believed to protect the body from harmful free radicals that can contribute to diseases such as cancer. Antioxidant vitamins include vitamin A, C, and E. However, doses too high may increase oxidative stress and therefore may increase cancer risk.

A diet rich in fruits and vegetables (containing B6, folate, and niacin) appears to protect against stomach cancer and in particular, intestinal cancer.

One study reported that cruciferous vegetables, especially broccoli, brussel sprouts, cauliflower, and cabbage were associated with a decreased risk of prostate cancer. Other foods, such as carrots, beans, and cooked tomatoes, also were associated with a lower risk.

A component of Vitamin E, tocotrienol, has been linked to a decreased risk of breast cancer in lab animals. Tocotrienol has been shown to readily kill tumor cells grown in culture. Tocotrienol is not the same type of substance found in generic Vitamin E supplements, but is plentiful in palm oil. Palm oil is difficult to obtain in the Western world, but lower concentrations of tocotrienol are found in rice bran oil and wheat bran oil. In 2004, research showed that the nutrient calcium and vitamin D worked together, not separately, to lower risk of colorectal cancer.

Researchers state that no single nutrient is the answer, but that the effects are cumulative and depend on eating a variety of fruits and vegetables. Because there are many more nutrients available in foods such as fruits and vegetables than in vitamin supplements, food is the best source for acquiring needed vitamins and minerals.

Special Concerns

For many years, debate has continued regarding taking vitamin supplements to prevent cancer. In 2004, 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. Beta-carotene supplements should not be used in patients with no symptoms because there is no evidence of risk reduction and some evidence that these supplements may cause harm to some patients.

There are concerns regarding antioxidant levels during chemotherapy and radiation therapy. Researchers report large amounts of Vitamin C are consumed by cancerous tumors during chemotherapy in studies with mice. Vitamin C is an antioxidant that consumes free radicals and is thought to perhaps interfere with the process of killing cancer cells during chemotherapy or radiation therapy. Cancer patients undergoing chemotherapy are advised against taking large amounts of Vitamin C. Another research study also has warned cancer patients about vitamin A and vitamin E during chemotherapy because it has demonstrated a protective effect on cancer cells in mice. These antioxidants may protect not only the normal cells from being destroyed, but also may protect dangerous cancer cells from being destroyed during cancer treatment. The researchers suggest an antioxidant-depleted diet may be prudent during cancer therapy.

Smokers are advised not to consume a diet high in beta-carotene (Vitamin A) because research has shown a link to increased lung cancer incidence.

Alternative and Complementary Therapies

There are a great many claims about particular vitamin and or antioxidants having beneficial health effects. Proper nutrition with an adequate diet is the best way to obtain vitamins, but a supplement may be required when intake is inadequate. It is important to check with a dietitian or doctor before taking nutritional supplements or alternative therapies because they may interfere with cancer medications or treatments.

Resources

Books

Quillin, Patrick, and Noreen Quillin. Beating Cancer With Nutrition—Revised. Sun Lakes, AZ: Bookworld Services, 2001.

Periodicals

"Calcium and Vitamin D Collaborate to Reduce Cancer Risk." Health & Medicine Week January 5, 2004: 190.

Sadovsky, Richard. "Can Vitamins Prevent Cancer and Heart Disease?" American Family Physician February 1, 2004: 631.

Singletary, Keith. "Diet, Natural Products and Cancer Chemoprevention." Journal of Nutrition 130 (2000): 465–6.

Willett, Walter C. "Diet and Cancer." The Oncologist 5, no. 5 (2000): 393–404.

Organizations

The National Cancer Institute (NCI). Public Inquiries Office: Building 31, Room 10A31, 31 Center Dr., MSC 2580, Betheseda, MD 20892-2580 (301) 435-3848, (800) 4-CANCER. , , .

National Center for Complementary and Alternative Medicine (NCCAM). 31 Center Dr., Room #5B-58, Bethesda, MD 20892-2182. (800) NIH-NCAM, Fax (301) 495-4957. .

Background

Vitamins are organic compounds that are necessary in small amounts in animal and human diets to sustain life and health. The absence of certain vitamins can cause disease, poor growth, and a variety of syndromes. Thirteen vitamins have been identified as necessary for human health, and there are several more vitamin-like substances that may also contribute to good nutrition. Originally, it was thought that vitamins were particular chemical compounds called amines, but now it is known that the vitamins are unrelated chemically. Their actions are different, and though exhaustively studied, not everything is understood about how they work and what they do. The vitamins are named by letters—vitamin A, vitamin C, D, E, K, and the group of B vitamins. The eight B vitamins were originally thought to be one vitamin, and as more was learned about them, they were given numeral subscripts: vitamin B,, B₂, etc. The B vitamins are now commonly called more aptly by chemically descriptive names: B, is thiamine, B₂ is riboflavin, B₆ and B₁₂ retain their numeral names, and the other B vitamins are niacin, pantothenic acid, biotin, and folic acid. The vitamins are found in plant and animal food sources. They have also been chemically synthesized and so can be ingested in their pure form as nutritional supplements. It is not known precisely how much of each vitamin each person needs, but there are recommended daily allowances for 10 vitamins.

Some researchers have made extravagant claims about the benefits of large doses of specific vitamins as either preventatives or cures for diseases from acne to cancer. As new discoveries are made and old claims are either debunked or reinforced often, it is safest to say that more is understood about the consequences of lack of vitamins than what particular vitamins may do. For example, deficiency of vitamin A leads to break-down of the photosensitive cells in the retina of the eye, causing night blindness. Absence of vitamin C in the diet leads to scurvy, a disease formerly the bane of sailors. Absence of vitamin D may lead to rickets, a bone disease.

History

Many researchers were responsible for piecing together the existence of vitamins as necessary components of the human and animal diets. One of the first people to study nutrition from a chemical standpoint was English physician William Prout. In 1827, he defined the three essentials of the human diet as the oily, the saccharin, and the albuminous, which in modern-day terms are fats and oils, carbohydrates, and proteins. In 1906, an English biochemist, Frederick Hopkins, discovered that mice fed on a pure diet of the three essentials could not survive unless they were given supplementary small amounts of milk and vegetables. A Polish scientist, Casimir Funk, coined the term vitamines in 1912 to describe the chemicals he believed were found in the supplementary food that helped the mice survive. Funk first believed that the vitamines were chemically related amines, thus vita (life) plus amines. As other vitamins were isolated that were not amines, the spelling of the word changed. Other researchers working on diseases such as scurvy and beriberi, which are caused by vitamin deficiency, contributed to the isolation of the different vitamins. Still, little was generally understood about vitamins at the beginning of the twentieth century. For instance, though the use of lime juice to prevent scurvy in sailors dates back to at least 1795, the physician who accompanied Scott's voyage to the South Pole in 1910 believed scurvy was caused by bacteria, and inadequate nutritional measures were taken to prevent the disease among the explorers. Between 1925 and 1955, the known vitamins were all isolated and synthesized. Research continues today on the function of the various vitamins.

Raw Materials

Vitamins can be derived from plant or animal products, or produced synthetically in a laboratory. Vitamin A, for example, can be derived from fish liver oil, and vitamin C from citrus fruits or rose hips. Most commercial vitamins are made from synthetic vitamins, which are cheaper and easier to produce than natural derivatives. So vitamin A may be synthesized from acetone, and vitamin C from keto acid. There is no chemical difference between the purified vitamins derived from plant or animal sources and those produced synthetically. Different laboratories may use different techniques to produce synthetic vitamins, as many can be derived from various chemical reactions.

Vitamin tablets or capsules usually contain additives that aid in the manufacturing process or in how the vitamin pill is accepted by the body. Microcrystalline cellulose, lactose, calcium, or malto-dextrin are added to many vitamins as a filler, to give the vitamin the proper bulk. Magnesium stearate or stearic acid is usually added to vitamin tablets as a lubricant, and silicon dioxide as a flow agent. These additives help the vitamin powder run smoothly through the tablet-making or encapsulating machine. Modified cellulose gum or starch is often added to vitamins as a disintegration agent. That is, it helps the vitamin compound break up once it is ingested. Vitamin tablets are also usually coated, to give the tablets a particular color or flavor, or to determine how the tablet is absorbed (in the stomach versus in the intestine, slowly versus all at once, etc.). Many coatings are made from a cellulose base. An additional coating of carnauba wax is often put on as well, to give the tablet a polished appearance.

Herbs of various kinds may be added to vitamin compounds, as well as minerals such as calcium, iron, and zinc. Typically, specialized laboratories produce purified vitamins and minerals. A distributor buys these from the laboratories and sells them to manufacturers, who put them together in different compounds such as multivitamin tablets or B-complex capsules.

The Manufacturing
Process

Preliminary check

• A vitamin manufacturer purchases raw vitamins and other ingredients from distributors. Raw vitamins from a reputable distributor arrive with a Certificate of Analysis, stating what the vitamins are and how potent they are. In many cases, the manufacturer will nevertheless test the raw materials or send samples to an independent laboratory for analysis. If herbs are to be an ingredient in the vitamin capsule, these must be tested for identity and potency, and for possible bacterial contamination as well.

Preblending

• Often, the raw vitamins arrive at the manufacturer in a fine powder, and they need no preliminary processing. However, if the ingredients are not finely granulated, they will be run through a mill and ground. Some vitamins may be preblended with a filler ingredient such as microcrystalline cellulose or malto-dextrin, because this produces a more even granule which aids further processing steps. Laboratory technicians may run test batches when working with new ingredients and determine if preblending is necessary.

Wet granulation

• For vitamin tablets, particle size is extremely important in determining how well the formula will run through the tabletting machine. In some cases, the raw vitamins arrive from the distributor milled to the appropriate size for tabletting. In other cases, a wet granulation step is necessary. In wet granulation, the fine vitamin powder is mixed with a variety of cellulose particles, then wetted. The mixture is then dried in a dryer. After drying, the formula may be in chunks as large as a dime. These chunks are sized by being run through a mill. The mill forces the chunks through a small hole of the desired diameter of the granule. These granules can then be weighed and mixed.

Weighing and mixing

• When all the vitamin ingredients are ready, a worker takes them to the weigh station and weighs them out on a scale. The required weights for each ingredient in the batch are listed on a formula batch record. After weighing, the worker dumps all the ingredients into a mixer. The volume of a typical mixer may be from 15-30 cu ft (0.42-0.84 cu m), though in a large manufacturing facility, it may be many times that large. The ingredients spend from 15 to 30 minutes in the mixer. At this point, samples are taken from different sides of the mixer and checked in the laboratory. The lab technicians verify that all the ingredients are distributed in the same proportion throughout the mix. If the manufacturer is making a large batch, workers may check the first three or four lots in the mixer, and then only re-check periodically. After mixing is complete, workers take the vitamin formula to either an encapsulating or a tablet-making machine.

Encapsulating machine

• If the lot in the mixer has been approved, workers tote the mixture to the encapsulating machine and dump it in a hopper. At the beginning of a batch, workers will test-run the encapsulating machine and check that the capsules are the proper and consistent weight. Workers also check the capsules visually to see if they seem to be splitting or dimpling. If the test batches run correctly, workers run the entire batch. The vitamin mixture flows through one hopper, and another hopper holds whole gelatin capsules. The capsules are broken into halves by the machine. The bottom half of the capsule falls through a funnel into a rotating dosing dish. Then the machine measures a precise amount of the powdered vitamin mixture into each open capsule half. Tamping pins push the powder down. Then the top halves of the capsules are pushed down onto the filled bottoms.

Polishing and inspection

• The filled vitamin capsules are next run through a polishing machine. The vitamins are circulated on a belt through a series of soft brushes. Any excess dust or vitamin powder is removed from the exterior of the capsules by the brushes. The polished capsules are then poured onto an inspection table. The inspection table has a belt of rotating rods. The vitamins fall in the grooves between the rods, and the vitamins rotate as the rods turn. Thus, all sides of the vitamin are visible for the inspector to see. The inspector removes any capsules that are too long, split, dimpled, or otherwise imperfect. The vitamins that pass inspection are then taken over to the packaging area.

Tableting

• Vitamin tablets are made in a tableting machine. After the vitamin blend has been mixed in the mixer, workers dump it into a hopper above the machine. The vitamin powder then flows through the hopper to a filling station beneath, and flows from there to a rotating table. The rotating table may be 2-4 ft (0.6-1.2m) in diameter, or even bigger, and is fitted with holes on its outside edge that hold dies in the shape of the desired tablet (oval, round, animal, etc.). The dies are interchangeable, so the same table can produce whatever shape the manufacturer wishes, as long as the proper dies are installed. The vitamin powder flows from the filling station to fill the die. When the table rotates, the filled die moves into a punch press. When the upper and lower halves of the punch meet, 4-10 tons (3.6-9 metric tons) of pressure is exerted on the vitamin powder. The pressure compresses the vitamin powder into a compact tablet. The punch releases, and the lower punch lifts to eject the tablet. Some tableting machines may have two punches, one on each side, so two tablets are made simultaneously. The speed of the rotation of the table determines how many tablets are made per minute. The tablets eject onto a vibrating belt which vibrates any loose dust off the tablets. The tablets then are moved to the coating area.

Coating

• 8 Vitamin tablets are usually coated for a variety of reasons. The coating may make the tablet easier to swallow. It may mask an unpleasant taste, and it may give the tablet a pleasant color. A manufacturer may coat in two different colors tablets that are the same size and shape, for identification. Tablets may also be given an enteric coating—a pH sensitive chemical coating that resists gastric acid. Tablets with an enteric coating will not break open in the stomach, but move to the intestine before dissolving. Other coatings determine the timing of the tablet's dissolution, so the vitamins can be absorbed slowly, or all at once, depending on what is appropriate to that tablet.

  Once the tablets are taken from the tableting area, they are placed in the coating pan. The coating pan is a large rotating pan surrounded by one to six spray guns operated by pumps. As the tablets revolve in the pan, the pumps spray coating over them. Many tablets also receive a second coating of carnauba wax. After air drying, the tablets are ready for packaging. The packaging step is the same for tablets as for capsules.

Packaging

• Packaging the vitamins takes several steps, and different machines carry out these steps. So in the packaging area, the vitamins pass through a row of machines. Once the vitamins are dumped in the hopper of the first machine, no human touches them. The worker sets the machine to count out the required number of capsules or tablets per bottle, and the rest is done automatically. The capsules or tablets fall into a bottle, and the bottle is passed to the next machine to be sealed, capped, labelled, and shrink-wrapped. The finished bottles are then set in boxes and are ready for distribution.

Quality Control

Checks for quality are taken at many stages of vitamin manufacturing. All the ingredients of vitamin tablets or capsules are checked for identity and potency before they are used. Often this is tested both by the raw vitamin distributor and by the manufacturer. The mixed vitamin powder is checked before it is tableted or encapsulated, and the finished product is also thoroughly inspected. Federal regulations govern what substances can be used in vitamins and what claims manufacturers can make for their products. Vitamin ingredients must be proven safe before they can be made available to consumers.

The Future

Vitamin research is a volatile field, with new studies constantly suggesting new roles for vitamins in health and prevention of disease. Certain vitamins or vitamin-like substances go through fads of consumer popularity as some of this research surfaces. Nevertheless, the manufacturing process remains the same for new substances. The future of vitamins will likely change most conceptually, in how much we understand about how vitamins work.

Where to Learn More

Books

Bender, David A. Nutritional Biochemistry of the Vitamins. Cambridge University Press, 1992.

Hendler, Sheldon Saul. The Doctor's Vitamin and Mineral Encyclopedia. Simon and Schuster, 1991.

Lieberman, Shari and Nancy Bruning. The Real Vitamin & Mineral Book. Avery Publishing Group, 1990.

[Article by: Angela Woodward]

An organic compound required in very small amounts for the normal functioning of the body and obtained mainly from foods. Vitamins are present in food in minute quantities compared to the other utilizable components of the diet, namely, proteins, fats, carbohydrates, and minerals.

Synthetic and natural vitamins usually have the same biological value. Different vitamins, which are often not related to each other chemically or functionally, are conventionally divided into a fat-soluble group (vitamins A, D, E, and K) and a water-soluble group [vitamin C (ascorbic acid) and the various B vitamins: thiamine, vitamin B, riboflavin, vitamin B₂, vitamin B₆, niacin, folic acid, vitamin B₁₂, biotin, and pantothenic acid]. The vitamins, particularly the water-soluble ones, occur almost universally throughout the animal and plant kingdoms individual articles on each vitamin.

The B vitamins function as coenzymes that catalyze many of the anabolic and catabolic reactions of living organisms necessary for the production of energy; the synthesis of tissue components, hormones, and chemical regulators; and the detoxification and degradation of waste products and toxins. On the other hand, vitamin C and the fat-soluble vitamins do not function as coenzymes. Vitamins C and E and β-carotene (a precursor of vitamin A) act as antioxidants, helping to prevent tissue injury from free-radical reactions. In addition, vitamin C functions as a cofactor in hydroxylation reactions. Vitamin D has hormonelike activity in calcium metabolism; vitamin A plays a critical role in night vision, growth, and maintaining normal differentiation of epithelial tissue; and vitamin K has a unique posttranscriptional role in the formation of active blood-clotting factors. See also Antioxidant; Carotenoid; Coenzyme; Nutrition.

Thirteen organic substances are essential to human life in very small amounts. Eleven of these must be supplied in the diet (vitamins A, B₁, B₂, B₆, B₁₂, C, E, K, folate, biotin, and pantothenate); two (niacin and vitamin D) can be made in the body if there is sufficient of the amino acid tryptophan, and exposure to sunlight respectively.

The word may be pronounced either ‘vaitamin’ or ‘vitamin’.

The vitamins

One of a group of potent, non-protein, organic compounds required in small amounts for the maintenance of normal health and metabolic integrity. Deficiency leads to specific clinical signs that respond only to restoration of the vitamin. They are essential in the diet because they cannot be made in the body (with the exception of vitamin D and niacin). So far, 13 compounds have been classed as true vitamins. Several other substances, such as laetrile and pangamic acid, have been described as vitamins but these compounds do not meet the strict definition of a vitamin. Although vitamins form a diverse and chemically unrelated group, they are classified as fat-soluble vitamins or water-soluble vitamins.

FAT-SOLUBLE VITAMINS
• vitamin A (retinol; carotene is an important precursor of vitamin A)
• vitamin D (ergocalciferol and cholecalciferol)
• vitamin E (tocopherol)
• vitamin K (phylloquinone from plants; menaquinone from gut bacteria)

WATER-SOLUBLE VITAMINS
• vitamin B₁ (thiamin)
• vitamin B₂ (riboflavin)
• vitamin B₆ (pyridoxine)
• vitamin B₁₂ (cobalamin)
• niacin (nicotinic acid and nicotinamide)
• pantothenic acid
• biotin
• folic acid
• vitamin C (ascorbic acid)

Each vitamin has a specific function; one vitamin cannot substitute for another. Lack of any one vitamin in the diet leads to ill health and eventually a deficiency disease. In addition, many body functions require the interaction of several vitamins, and the lack of one may undermine the function of others.

The relationship between vitamin requirements and exercise is complex, and the subject of much debate. There is some dispute about whether active people require more of every type of vitamin. However, it is generally agreed that requirements of the B-complex vitamins, which play many diverse roles in energy metabolism, are directly related to calorie expenditures of up to 5000 Calories per day. On this basis, some coaches believe that very active people may need at least twice the recommended daily amounts of these vitamins. Many sports nutritionists maintain that this increased demand for vitamins can be satisfied by eating a well-balanced diet. They argue that, as energy expenditure increases, food intake and therefore vitamin intake will also increase. On the other hand, some coaches advocate the use of vitamin supplements, arguing that increased dietary intake alone cannot guarantee a sufficient vitamin intake. See also vitamin supplementation.

One of a number of unrelated organic substances that occur in small amounts in food and are required for normal metabolic activity. The vitamins may be water soluble or fat soluble.

Definition

Vitamins are organic components in food that are needed in very small amounts for growth and for maintaining good health. The vitamins include vitamins D, E, A, and K (fat-soluble vitamins), and folate (folic acid), vitamin B₁₂, biotin, vitamin B₆, niacin, thiamin, riboflavin, pantothenic acid, and vitamin C (ascorbic acid) (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 causes rickets, a disease of the bones. Vitamin E deficiency occurs only very rarely and causes nerve damage. Vitamin A deficiency, common throughout the poorer parts of the world, causes night blindness. Severe vitamin A deficiency can result in xerophthalmia, a disease that, if left untreated, results in total blindness. Vitamin K deficiency results in spontaneous bleeding. Mild or moderate folate deficiency, common throughout the world, 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, which involves skin rashes and scabs, diarrhea, and mental depression. Thiamin deficiency results in beriberi, a disease resulting in atrophy, weakness of the legs, nerve damage, and heart failure. Vitamin C deficiency results in scurvy, a disease that involves bleeding. Diseases associated with deficiencies in vitamin B₆, riboflavin, or pantothenic acid have not been found in the 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. Rarely, deficiency in B₆ results in neurologic problems. Issues of toxicity are connected to the over consumptions of vitamins, particularly E, K, and B. Also, lack of regulation in the vitamin industry means consumers ought only to buy well-known brands.

Some of the vitamins serve only one function in the body, while other vitamins serve a variety of unrelated functions. Hence, some vitamin deficiencies tend to result in one type of defect, while other deficiencies result in a variety of problems.

Description

Vitamin treatment is usually 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 persons with diseases that prevent absorption of fat-soluble vitamins. Oral vitamin supplements are especially useful for persons 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 which 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 to 1,000 times greater than the RDA. Pernicious anemia, homocystinuria, and biotinidase deficiency are three examples of genetic diseases which are treated with megadoses of vitamins.

General Use

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 is often 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.

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 in certain women by folic acid supplements.

Vitamin treatment is important during specific diseases in which 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 use 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 percent of the general population, and 2–3 percent of the elderly, may have the disease. If left untreated, pernicious 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 in the early 2000s a matter of debate and ongoing research. For example, vitamin C is not proven to prevent the common cold. Yet millions of Americans take it for that reason. Consumers should ask a physician or pharmacist for more information on the appropriate use of multivitamin supplements.

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

The 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.

Precautions

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

Side Effects

Few side effects are associated with vitamin treatment if vitamins are taken within the prescribed dosages. Excessive intake of some B vitamins may impart a greenish color to urine. Any possible risks depend on the vitamin and the reason why it was prescribed. Consumers should ask a physician or pharmacist about how and when to take vitamin supplements, particularly those that have not been prescribed by a physician.

Parental Concerns

The dosage of vitamin supplements should not exceed the recommended daily allowance without a recommendation by a physician. Recommended dosages vary with age, so parents should be should to give vitamins to children that are specially formulated for children. Vitamin bottles will list recommended doses for different age groups. Infants and toddlers may also benefit from vitamin supplements if they do not eat a variety of foods. Liquid vitamin supplements are available commercially for these young children.

Resources

Books

Heird, William C. "Vitamin Deficiencies and Excesses." In Nelson Textbook of Pediatrics, 17th ed. Edited by Richard E. Behrman et al. Philadelphia: Saunders, 2003, pp. 177–90.

Litwack, Gerald. Vitamins and Hormones. St. Louis, MO: Elsevier, 2004.

Mason, Joel B. "Consequences of Altered Micronutrient Status." In Cecil Textbook of Medicine, 22nd ed. Edited by Lee Goldman et al. Philadelphia: Saunders, 2003, pp. 1326–35.

Navarra, Tova. Encyclopedia of Vitamins, Minerals, and Supplements. New York: Facts on File, 2004.

Russell, Robert M. "Vitamin and Trace Mineral Deficiency and Excess." In Harrison's Principles of Internal Medicine, 15th ed. Edited by Eugene Braunwald et al. New York: McGraw-Hill, 2001, pp. 461–9.

Periodicals

Bryan, J., et al. "Nutrients for cognitive development in school-aged children." Nutrition Reviews 62, no. 8 (2004): 295–306.

Fennell, D. "Determinants of supplement usage." Preventive Medicine 39, no. 5 (2004): 932–9.

Krapels, I. P., et al. "Maternal nutritional status and the risk for orofacial cleft offspring in humans." Journal of Nutrition 134, no. 11 (2004): 3106–13.

Mossad, S. B. "Current and future therapeutic approaches to the common cold." Expert Review of Anti-Infective Therapy 1, no. 4 (2004): 619–26.

Organizations

American Academy of Family Physicians. 11400 Tomahawk Creek Parkway, Leawood, KS 66211–2672. Web site: www.aafp.org/.

American Academy of Pediatrics. 141 Northwest Point Boulevard, Elk Grove Village, IL 60007–1098. Web site: www.aap.org/default.htm.

American Association of Naturopathic Physicians. 8201 Greensboro Drive, Suite 300, McLean, VA 22102. Web site: .

American College of Obstetricians and Gynecologists. 409 12th St., SW, PO Box 96920, Washington, DC 20090–6920. Web site: www.acog.org/.

Web Sites

"Dietary Reference Intakes Tables: Vitamins Table." Institute of Medicine of the National Academies. Available online at www.iom.edu/file.asp?id=7296 (accessed January 9, 2005).

"Vitamins." Harvard School of Public Health. Available online at www.hsph.harvard.edu/nutritionsource/vitamins.html (accessed January 9, 2005).

"Vitamins." National Library of Medicine. Available online at www.nlm.nih.gov/medlineplus/ency/article/002399.htm (accessed January 9, 2005).

"Vitamins and Minerals." Food and Nutrition Information Center. Available online at www.nal.usda.gov/fnic/etext/000068.html (accessed January 9, 2005).

"Vitamins and Minerals." West Virginia Dietetic Association. Available online at www.wvda.org/nutrient/ (accessed January 9, 2005).

[Article by: L. Fleming Fallon, Jr., MD, DrPH]

For more information on vitamin, visit Britannica.com.

A member of a group of potent non-protein organic compounds required in minute amounts for good health and growth. Vitamins (except vitamin D) cannot be synthesized by the body and are therefore essential constituents of the diet. They are classified as fat-soluble vitamins (e.g. vitamins A, D, E, and K) or water soluble vitamins (e.g. vitamins B and C). Many vitamins seem to act as coenzymes or are involved in the production of coenzymes. Each vitamin has a specific function; one vitamin cannot substitute for another. Many metabolic reactions require several vitamins and lack of one may hinder the activity of others. There is much disagreement about the effects of exercise on vitamin requirements. Many coaches believe that the added stress experienced by elite athletes makes greater demands on their vitamin requirements, and that they suffer a greater risk of vitamin deficiency than sedentary people. Currently there is much research being undertaken to establish the precise vitamin needs of athletes.