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.
|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|
|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
|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
|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||Helps the liver eliminate toxins|
|Folic Acid (Folate, Folacin)||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|
|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|
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.
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.
Oncology Encyclopedia: Vitamins
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.
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
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.
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.
Quillin, Patrick, and Noreen Quillin. Beating Cancer With Nutrition—Revised. Sun Lakes, AZ: Bookworld Services, 2001.
"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.
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. .