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Dietary fiber refers to the components found in the cell walls in plants, namely pectin, hemicelluloses, cellulose, lignin, fructans, gums, and beta-glucans. All fruits and vegetables contain these components. The amount of the type of fiber varies in each fruit and vegetable and also depends on the age of the food. For example, vegetables that are harvested during the earlier part of their growth phase are likely to contain higher levels of pectin and hemicelluloses (soluble fiber) and less cellulose and lignin (insoluble fiber) than when harvested at a later stage.
Fiber performs some critical functions in the body. Soluble fiber, for example, prolongs the time it takes to empty the stomach of food so sugars are released and absorbed more slowly. This helps keep energy levels on an even keel and also helps people who have diabetes regulate their blood sugar levels. Soluble fiber also helps lower total and LDL cholesterol levels, which reduces the risk of heart disease, and also binds with fatty acids.
Insoluble fiber has a significant impact on the intestinal tract, as it promotes regular bowel movements, helps prevent constipation, removes toxins through the colon in less time, and helps prevent colon cancer by keeping an optimal pH level in the intestinal tract, which prevents microbes from producing cancerous substances.
Fiber’s ability to bind to carcinogens and other harmful substances and assist in eliminating them from the body can be helpful in reducing the risk of prostate cancer. Soluble fiber appears to bind to testosterone, which makes it less available to stimulate the growth of prostate tumors. Insoluble fiber lowers testosterone levels by increasing excretion of the hormone. In a study of the impact of soluble and insoluble fiber on PSA levels, the researchers found that when men followed a diet high in soluble fiber for four months, their PSA levels declined by 10 percent. (Tariq 2000)
High-fiber foods like legumes and beans contain a chemical called inositol hexaphosphate (IP-6). Thus far animal studies have indicated that IP-6 protects prostate tissue (Singh 2003) and that supplementing the diet with IP-6 may help prevent prostate tumors from developing. (Singh 2004) So far, however, no studies in humans have been done.
A team of researchers at the University of Georgia found that the fiber pectin kills prostate cancer cells. Pectin is found naturally in fruits and vegetables, while prepared pectin is extracted from citrus peels and apples. In the 2007 study, the scientists found that when they exposed prostate cancer cells to pectin, the number of cancerous cells declined by 40 percent. (Jackson 2007) It appears that prostate cancer cells self-destruct when pectin binds to the receptors of the cell surface. Pectin does not bind to non-cancerous cells and so has no impact on them.
Other research has indicated that pectin may be helpful in fighting liver and colon cancer in lab animals and in reducing metastasis, further evidence that this phytonutrient may be beneficial in the fight against prostate cancer. (Liu 2008; Huang 2008)
Good dietary sources of soluble fiber are oranges and apples, carrots, dried beans and peas, nuts, barley, flax seed, oats, and oat bran. Insoluble fiber sources include green beans, dark green leafy vegetables, skins of fruits and root vegetables, nuts, seeds, and whole-wheat products.
The National Academy of Sciences’ Institutes of Health recommends that men ages 19 to 50 consume 38 grams of fiber daily, and 30 grams after age 50. Natural fiber supplements can help individuals reach these goals if they are not getting enough from their diet. Follow individual package directions when using fiber supplements. Because fiber supplements may reduce or delay the body’s absorption of certain medications, take medications at least 1 hour before or 2 to 4 hours after using a fiber supplement.
See also:
Modified citrus pectin kills prostate cancer cells
References
Huang ZL, Liu HY. Expression of galectin-3 in liver metastasis of colon cancer and the inhibitory effect of modified citrus pectin. Nan Fang Yi Ke Da Xue Xue Bao 2008 Aug; 28(8): 1358-61.
Jackson CL, Dreaden TM, Theobald LK, Tran NM, Beal TL et al. Pectin induces apoptosis in human prostate cancer cells: correlation of apoptotic function with pectin structure. Glycobiology 2007 Aug; 17(8): 805-19.
Liu HY, Huang ZL, Yang GH, Lu WQ, Yu NR. Inhibitory effect of modified citrus pectin on liver metastases in a mouse colon cancer model. World J Gastroenterol 2008 Dec 28; 14(48): 7386-91.
Singh RP, Agarwal C, Agarwal R. Inositol hexaphosphate inhibits growth and induces G1 arrest and apoptotic death of prostate carcinoma DU145 cells: modulation of CDKI-CDK-cyclin and pRb-related protein-E2F complexes. Carcinogenesis 2003 Mar; 24(3): 555-63.
Singh RP, Sharma G, Mallikarjuna GU, Dhanalakshmi S, Agarwal C, Agarwal R. In vivo suppression of hormone-refractory prostate cancer growth by inositol hexaphosphate: induction of insulin-like growth factor binding protein-3 and inhibition of vascular endothelial growth factor. Clin Cancer Res 2004 Jan 1; 10(1 Pt 1): 244-50
Tariq N, Jenkins DJ, Vidgen E, Fleshner N, Kendall CW et al. Effect of soluble and insoluble fiber diets on serum prostate specific antigen in men. J Urol 2000 Jan; 163(1): 114-18
