Digestive / Colonic Health
“Our scientific interest in resistant starch is that resistant starch is turning out to be as important, and possibly more important, than [traditional] fiber for the health of the human bowel.”
- Dr. David Topping, Chief Research Scientist,
CSIRO Health Sciences and Nutrition
Maintaining digestive health is critical to maintaining overall health and wellness due to the fact that the body's digestive system provides many critical functions. Not only does the digestive system break down food to provide essential energy and nutrients, it is also a critical component of the immune and endocrine systems. Resistant starch from high amylose corn helps maintain a healthy colon and a healthy digestive system via several mechanisms:
- Resistant starch promotes regularity with a mild laxative effect1
- Resistant starch selectively increases beneficial bacteria – it is a ‘prebiotic’ fiber2
This picture illustrates colonic bacteria (smaller rod shapes) adhered to and in the process of consuming a large resistant starch granule.3
· The fermentation of resistant starch increases short-chain fatty acids in the colon. The fermentation of resistant starch produces more butyrate than other fibers tested.4 Butyrate is particularly important because it is the primary energy source for colonic cells and has anti-inflammatory properties that are important for keeping colon cells healthy.5, 6
In addition, butyrate has anti-carcinogenic properties. Published research has shown that butyrate inhibits the growth and proliferation of tumor cell lines in vitro7, it induces differentiation of tumor cells, producing a phenotype similar to that of the normal mature cell, 8 and it induces apoptosis or programmed cell death of human colorectal cancer cells.
· The fermentation of resistant starch reduces intestinal pH and the production of potentially harmful secondary bile acids, ammonia and phenols.9
· Resistant starch prevents the degradation of the mucous layer within the colon. This mucous layer is believed to protect colon cells.10
· Resistant starch may help to reduce the risk of colorectal cancer. Three mechanisms are believed to be involved in the protection against the development and growth of cancer cells – initiation, differentiation and apoptosis. Resistant starch has been shown to protect colon cells from DNA damage11; to promote the normalization (i.e. differentiation) of cancerous cells within the colon and increase the apoptosis (programmed cell death) of cells damaged by carcinogens.12 A recent clinical study found that resistant starch reduced the proportion of mitotic cells in the top half of colonic crypts (a marker for pre-malignancy), and increased expression of cell cycle regulatory genes in patients with colorectal cancer. 13 A recent published multi-center clinical trial concluded that resistant starch was not effective in preventing colon cancer in individuals genetically predisposed to colon cancer (individuals wih Larch Syndrome).14
An international comparison of dietary consumption and colorectal cancer incidence is supportive.15
This study found a linear correlation between starch intake and reduced risk of colorectal cancer but did not find a correlation between dietary fiber intake and colorectal cancer. Because approximately 5% of all starch consumed resists digestion, the correlation between increased starch consumption and reduced risk of colorectal cancer may be linked to the fermentation of resistant starch.
References
1. Young GP, Le Leu K. Resistant starch and colorectal neoplasia. The Journal of AOAC International 2004; 87(3):775-86.
2. Brown I, Warhurst M, Arcot J, Playne M, Illman RJ, Topping DL, “Fecal numbers of bifidobacteria are higher in pigs fed Bifidobacterium longum with a high amylose cornstarch than with a low amylose cornstarch” The Journal of Nutrition, 1997;127:1822-1827.
3. Brown, Microbiology Australia 1999.
4. Cummings, American Journal of Clinical Nutrition.
5. Scheppach W. Effects of short chain fatty acids on gut morphology and function. Gut 1994;35(1 Suppl):S35-8.
6. Andoh A, Tsujikawa T, Fujiyama Y. Role of dietary fiber and short-chain fatty acids in the colon. Current Pharmaceutical Design 2003;9(4):347-58.
7. A Toscani, D.R. Soprano, K.J. Soprano. Molecular analysis of sodium butyrate-induced growth arrest. Oncogene Research, 1988; 3, 223-38.
8. R.H. Whitehead, G.P. Young, P.S. Bhathal. Effects of short chain fatty acids on a new human carcinoma cell line, (LIM1215) Gut 1986; 27, 1457-63.
9. Birkett A, Muir J, Phillips J, Jones G, O'Dea K. Resistant starch lowers fecal concentrations of ammonia and phenols in humans. The American Journal of Clinical Nutrition 1996; 63(5):766-72.
10. Toden S, Bird AR, Topping DL, Conlon MA. Resistant starch prevents colonic DNA damage induced by high dietary cooked red meat or casein in rats. Cancer Biology & Therapy 2006, in press.
11. Le Leu, R.K., Brown, I.L., Hu, Y., Morita, T., Esterman, A., Young, G.P. Effect of dietary resistant starch and protein on colonic fermentation and intestinal tumourigenesis in rats. Carcinogenesis (Feb 2007), 28(2):240-5. [Epub 2006 Dec 13]. See also Toden S., Bird, A.R., Topping, D.L., Conlon, M.A. Differential effects of dietary whey, casein and soya on colonic DNA damage and large bowel SCFA in rats fed diets low and high in resistant starch. British Journal of Nutrition, (2007), 97(3), 535-543. See also Toden, S., Bird, A.R., Topping, D.L., Conlon, M.A. High red meats diets induce greater numbers of colonic DNA double-strand breaks than white meat in rats: attenuation by high-amylose maize starch. Carcinogenesis, (2007), 28(11), 2355-2362. See also Toden, S., Bird, A.R., Topping, D.L., Conlon, M.A. Dose-dependent reduction of dietary protein-induced colonocyte DNA damage by resistant starch in rats correlates more highly with caecal butyrate than with other short chain fatty acids. Cancer Biology & Therapy, (2007), 6 (2), E1-E6.
12. Le Leu RK, Brown IL, Hu Y, Bird AR, Jackson M, Esterman A, Young GP. A synbiotic combination of resistant starch and Bifidobacterium lactis facilitates apoptotic deletion of carcinogen-damaged cells in rat colon. Journal of Nutrition 2005:135:996-1001.
13. Dronamraju SS, Coxhead JM, Kelly SB, Burn J, Mathers JC. Cell kinetics and gene expression changes in colorectal cancer patients given resistant starch - A randomized ontrolled trial. Gut Online Online First article available Oct 31, 2008. doi: 10.1136/gut.2008.162933.
14. Burn J, Bishop T, Mecklin JP, Macrae F, Moslein, G, Olschwang S, Bisgaard ML, Ramesar R, Eccles D, Maher ER, Bertario L, Jarvinen HJ, Lindblom A, Evans G, Lubinski J, Morrison P, Ho JWC, Vasen HFA, Side L, Thomas HJW,Scott RJ, Dunlop M, Barker G, Elliott F, Jas JR, Fodde R. Lynch HT, Mathers JC. Effect of aspirin or resistant starch on colorectal neoplasia in the Lynch Syndrome. New England Journal of Medicine, 2008;359;24:2567-78.
15. Cassidy A, Bingham SA, Cummings JH. Starch intake and colorectal cancer risk: an international
comparison. The British Journal of Nutrition 1994; 69:937-42.
The Stats
· Over 145,000 people will be diagnosed with colorectal cancer (cancer of the colon or rectum) in 2005. Of those, more than 56,000 will die of the diseasea
· Cancers of the colon or rectum combined are the third most common type of cancer and the second most common cause of cancer in the U.S.a
· Nearly 3 million Americans have Celiac disease (leading to gluten intolerance).
· It is estimated that more than 600,000 people in the United States have some form of inflammatory bowel disease.b
The Role of Resistant Starch
Eating natural resistant starch, a form of fiber which minimally affects food flavor and texture, is important for colon health. Recent scientific studies suggest that resistant starch may reduce the risk for colon cancer via its production of butyrate through fermentation within the colon. It may also have an impact on those who are gluten intolerant or have inflammatory bowel disease.
a. American Cancer Society
b. Botoman VA, Kozarek RA. Inflammatory bowel disease. In: Taylor RB, ed. Difficult medical management. Philadelphia: Saunders, 1991:374-86