According to a study published in the New England Journal of Medicine (1999), this protective effect may be due to fiber's tendency to add bulk to your digestive system, shortening the amount of time that wastes travel through the colon. As this waste often contains carcinogens, it is best if it is removed as quickly as possible; so, increased fiber decreases chances for intestinal cells to be affected.
The Journal of Clinical Nutrition (1999) reported that Fiber may also help protect against breast cancer, an effect noted especially with consumption of whole grains and wheat bran. Additionally, studies suggest that high amounts of fiber may also prevent breast cancer by binding to estrogen. When bacteria in the lower intestine break down fiber, a substance called butyrate is produced which may inhibit the growth of tumors of the colon and rectum as reported in the Journal of Oncology Research in 2000. Fiber may also have a protective effect against mouth, throat, and esophageal cancers according to a study published in the International Journal of Cancer in 2001.
If you're like most North Americans, you take in only 10 to 15 grams of fiber per day. However, most studies have shown that optimal intake for cancer prevention is at least 30 to 35 grams per day. Recent studies suggest that small increases in fiber, such as adding vegetables to a chicken stir-fry or having a hamburger on a whole wheat bun, do not offer much protection. On the other hand, when we replace high-fat, animal products such as chicken, fish, cheese, and eggs with plant foods, we easily boost fiber to levels where real protection is possible.
Whole foods contain two types of dietary fiber which are known as soluble and insoluble. Soluble fiber dissolves in water and is found in a variety of fruits, vegetables, legumes, and grains. It cuts cholesterol and adds to your feeling of fullness. Good sources of soluble fiber are oats, oat bran, oatmeal, apples, citrus fruits, strawberries, dried beans, barley, rye flour, potatoes, raw cabbage, and pasta.
It is best to choose fiber-rich foods over fiber supplements in order to get the full range of the cancer-fighting phytochemicals that fruits, vegetables, legumes, and grains contain.