The Role of Vitamins, Specific Nutrients and the Development of Cancer

Antioxidants
Nutrients in fruits and vegetables protect the body against oxygen-induced damage that occurs constantly as a result of normal metabolism. Such damage is associated with increased cancer risk. Accordingly, these nutrients are thought to protect against cancer. This protective effect is seen only when these nutrients are taken as whole foods. Antioxidant supplements have not shown a reduction in cancer risk.
Artificial Sweeteners
No increase in the risk of cancer development has been shown from either saccharin or Aspartane.
Betacarotene
Betacarotene is an antioxidant and is found in fruits and vegetables. As a supplement, it has been shown ineffective in reducing cancer risk. Two studies have shown a higher risk of lung cancer in cigarette smokers taking betacarotene supplements.
Calcium
There is no proven relationship between the amount of calcium in the diet and a reduction in cancer risk. Calcium is important to reduce the risk of osteoporosis and is found in low fat and nonfat dairy products. It is also present in leafy vegetables and beans.
Carotenoids
Carotenoids are the pigments found in fruits and vegetables which have been shown to reduce the risk of cancer.
Cholesterol
Cholesterol in the diet is found only in meat, dairy products, eggs, and fats. There is no evidence as to whether cholesterol itself is responsible for an increase in cancer risk.
Coffee
Although coffee was at one time thought to increase the risk of cancer of the pancreas and breast, current studies have failed to confirm this relationship.
Cruciferous Vegetables
Vegetables which belong to the cabbage family and include broccoli, cauliflower, and brussel sprouts are thought to reduce the risk of colorectal cancer.
Fiber
Fiber is found in beans, vegetables, whole grains, and fruits. It is thought to reduce the risk of colorectal cancer; however, the way in which fiber acts is poorly understood.
Fish Oil
There is no evidence for a protective effect from fish oil in humans. As is the case with all fats, fish oils are high calorie foods.
Fluoride
Fluoride in toothpaste, the public water supply, and foods has not been shown to increase the risk of cancer.
Folic Acid
Folic acid is one of the B vitamins and is found in vegetables, beans, fruits, and whole grains. Supplements are recommended for women who are pregnant and have been shown to reduce the risk of spina bifida and other neural tube defects in their infants. To reduce the risk of cancer, folic acid should be consumed together with other nutrients found in whole foods.
Food Additives
There is no evidence at present that substances added to foods to preserve them and enhance color, flavor, or texture increase the risk of cancer in humans.
Garlic
Although numerous studies are ongoing, there is no specific role for this vegetable in cancer prevention at present.
Nitrites
Nitrites are not a significant cause of cancer. They are, however, found in lunch meats, ham, and hot dogs which are not considered healthful in large quantities.
Olestra
Olestra is a synthetic fat substitute and, as such, can reduce fat intake. It also reduces the absorption of fat soluable vitamins and other protective phytochemicals from fruits and vegetables. The effect of this fat substitute on the risk of cancer is unknown.
Olive Oil
The consumption of olive oil does not increase or decrease the risk of cancer.
Phytochemicals
There is no benefit from taking phytochemicals as supplements. They are, however, present in large quantities in fruits, vegetables, beans, and grains.
Salt
Moderate intake of salt is not associated with an increased risk of cancer.
Selenium
Selenium supplements are not recommended. Grains are the best source of natural selenium.
Soybeans
Soybeans appear to have a beneficial effect on hormone-dependent cancers in animals. Their effect in humans is unclear. They are, however, an excellent protein source and a good alternative to meat.
Supplements
As of yet, supplements are not recommended in lieu of whole foods. The complex relationship between nutrition and cancer risk is shown by the failure of many studies to demonstrate a positive influence of vitamin or mineral supplements on the development of cancer.
Tea
No beneficial effect of tea on the risk of developing cancer has been proven in humans.
Vitamin A
Supplements of vitamin A have not been shown to reduce the risk of cancer.
Vitamin C
Although vitamin C is found in many fruits and vegetables which are considered beneficial, supplements of vitamin C have not consistently been shown to reduce the risk of cancer.
Vitamin E
Vitamin E has not been shown to reduce the risk of cancer. It can, however, reduce the risk of coronary artery disease.

See also Nutrition.

Summary

The precise role of diet and physical activity in the reduction of cancer risk remains to be defined. The interaction of various nutrients in different food groups is complex. It is clear, however, that a high fat diet, obesity, and a sedantery lifestyle do predispose to the development of cancer, as well as to coronary artery disease.