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 B 6 (pyridoxine), pantothenic acid, niacin, biotin, folic acid (folate), and vitamin B 12 (cobalamin). Vitamins may also be referred to as micronutrients.
A guide to the amount an average person needs each day to remain healthy has been determined for each vita-min. In the United States, this guide is called the recommended daily allowance (RDA). Consumption of too little or too much of certain vitamins may lead to a nutrient deficiency or a nutrient toxicity respectively.
Consumption of a wide variety of foods, with adequate vitamin and mineral intake is the basis of a healthy diet. Good nutrition may assist in the prevention of cancer, or for those with existing malignancies, 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 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, lowfat 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
- 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 be detrimental to cancer risk.
One study reported that cruciferous vegetables, especially broccoli, brussel sprouts, cauliflower, and cabbage were associated with a decreased risk of prostate cancer. Other foods were also associated with a lower risk such as carrots, beans, and cooked tomatoes.
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.
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.
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 has also 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 vita-min 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.
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Quillin, Patrick, and Noreen Quillin. Beating Cancer With Nutrition—Revised. Sun Lakes, AZ: Bookworld Services, 2001.
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Willett, Walter C. "Diet and cancer." The Oncologist 5, no. 5(2000): 393-404.
National Center for Complementary and Alternative Medicine (NCCAM). 31 Center Dr., Room #5B-58, Bethesda, MD20892-2182. (800) NIH-NCAM, Fax (301) 495-4957.<http://nccam.nih.gov>.
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. <http://cancer.gov/publications/>, <http://cancertrials.nci.nih.gov>, <http://cancernet.nci.nih.gov>.
Crystal Heather Kaczkowski, MSc.
—A substance that prevents damage caused by free radicals.
—A term for diseases in which abnormal cells divide without control. Cancer cells can invade nearby tissues and can spread through the bloodstream and lymphatic system to other parts of the body.
—Free radicals are highly reactive chemicals that often contain oxygen. They are produced when molecules are split to give products that have unpaired electrons. This process is referred to as oxidation.
Malignant (also malignancy)
—Meaning cancerous; a tumor or growth that often destroys surrounding tissue and spreads to other parts of the body.
—A condition in which antioxidant levels are lower than normal. Antioxidant levels are usually measured in blood plasma.