According to the National Cancer Institute, as much as 80 percent of all cancers are due to identified factors, and thus are potentially preventable. Thirty percent are due to tobacco use, and as much as 35 percent to 50 percent are due to foods. It is easy to control these and other risk factors.

What Is Cancer?

Cancer begins as a single abnormal cell that begins to multiply out of control. Groups of such cells form tumors and invade healthy tissue, often spreading to other parts of the body. Carcinogens are substances that promote the development of cancerous cells. They may come from foods, from the air, or even from within the body. Most carcinogens are neutralized before damage can occur, but sometimes they attack the cell’s genetic material (DNA) and alter it. It takes years for a noticeable tumor to develop.  Some vitamins in plant foods are known to be inhibitors. Dietary fat, on the other hand, is known to be a promoter that helps the abnormal cells grow quickly.

Fiber Fights Cancer

High-fiber diet reduces diseases of the digestive tract. He observed that in countries where diets are high in fiber (that is, plant-based diets), there were fewer cases of colon cancer. By definition, fiber cannot be digested by humans early in the digestive process. It moves food more quickly through the intestines, helping to eliminate carcinogens. It also draws water into the digestive tract. The water and fiber make fecal matter bulkier, so carcinogens are diluted.

Fiber is also protective against other forms of cancer. Studies have shown that stomach cancer and breast cancer are less common on high-fiber diets. Fiber affects levels of estrogens in the body. Estrogens are normally secreted into the intestine, where the fiber binds with the hormone and moves it out of the body. Without adequate fiber, the estrogen can be reabsorbed from the intestine into the bloodstream. High levels of estrogen are linked to a higher risk of breast cancer. The best sources of fiber are whole grains, beans, peas, lentils, vegetables, and fruits. Foods that are closest to their natural state, unrefined and unpeeled, are highest in fiber.

Fat Raises Cancer Risks

Many studies indicate that fat in foods increases one’s risk for cancer, and it may also adversely affect breast cancer survival rates for those who have cancer. Although the total amount of fat one eats is of concern, there is evidence that animal fat is much more harmful than vegetable fat. 

How Fat Affects Cancer Risks

Fat has many effects within the body. It increases hormone production and thus raises breast cancer risks. It also stimulates the production of bile acids which have been linked to colon cancer.

The average diet in the United States is about 37 percent fat. The National Cancer Institute suggests that people lower that percentage down to 30 percent; however, studies have shown that fat intake should be well below 30 percent to have an anti-cancer affect. Ten to 15 percent is more likely to be helpful.

The Importance of Vegetables

Not only are vegetables low in fat and high in fiber, they also contain many cancer-fighting substances. Carotenoids, the pigment that gives fruits and vegetables their dark colors, have been shown to help prevent cancer. Beta-carotene, present in dark green and yellow vegetables, helps protect against lung cancer and may help prevent cancers of the bladder, mouth, larynx, esophagus, breast, and other sites.

Vegetables such as cabbage, broccoli, kale, turnips, cauliflower, and Brussels sprouts contain flavones and indoles which are thought to have anti-cancer activities.

Vitamin C, found in citrus fruits and many vegetables, may lower risks for cancers of the esophagus and stomach. Vitamin C acts as an antioxidant, neutralizing cancer-causing chemicals that form in the body. It also blocks the conversion of nitrates to cancer-causing nitrosamines in the stomach.

Selenium is found in whole grains and has the same antioxidant effects as vitamin C and beta-carotene. Vitamin E also has this effect. Caution is advised in supplementing selenium, which is toxic in large doses.

Vegetarians Are Better Off

All the evidence points to a low-fat, high-fiber diet that includes a variety of fruits, vegetables, whole grains, and beans, as being the best for cancer prevention. Vegetarians have about half the cancer risk of meat-eaters.

Vegetarians have higher blood levels of beta-carotene. They consume more vitamin C, beta-carotene, indoles, and fiber than meat-eaters. Vegetarians also have stronger immune systems. Natural killer cells are specialized white blood cells that attack and neutralize cancer cells. Also, vegetarians tend to eat more soy products than meat-eaters. Soybeans contain many substances that are anticarcinogens, including lignans and phytoestrogens. A diet that is rich in soybeans may be one reason for the lower incidence of breast cancer in Asia.

Conclusion

A cancer prevention diet is one that is high in fiber, low in fat (especially animal fat), and includes generous portions of fruits and vegetables. It also minimizes or excludes alcohol. The best diets are pure vegetarian diets.