7-3 |
Effects of resistant starch on colonic function: Potential health benefits |
I. ROWLAND, Northern Ireland Centre for Diet and Health, Univ. of Ulster, Cromore Rd., Coleraine, BT52 1SA, United Kingdom Evidence suggests that the type of carbohydrate in the diet can effect gut function, particularly events in the colonic mucosa, possibly influencing colon cancer. Dietary carbohydrates, such as resistant starch (RS) that are poorly digested and hence pass intact into the large bowel are likely to have the greatest effect on the colon. The differential effects of sucrose and various starches on gut microflora composition and metabolic activity in germ-free rats associated with a human intestinal microflora ('HFA rats') were studied. Groups of HFA rats were fed a high sucrose diet, or diets containing maize (digestible) starch, or a retrograded amylomaize RS - CrystaLean®. Rats fed the CrystaLean diet, compared to rats fed sucrose had a significant increase in colon lactobacilli and bifidobacteria and a decrease in enterobacteria and staphylococci counts. Activity of the enzyme ß-glucuronidase, ammonia concentration and formation of the direct acting genotoxin 7-OHIQ were highest in the sucrose-fed group, and lowest in the RS fed rats. Furthermore, CrystaLean-fed rats exhibited a greater proportion of n-butyric acid in the caecum than the sucrose or digestible-starch fed animals. Butyric acid has been associated with induction of apoptosis and inhibition of growth in colon cancer cell lines. Equivocal results were obtained in a second and related rat study. The feeding of CrystaLean was associated with a significant increase in mucosal cell proliferation in the rat colonic mucosa, but carcinogen-induced DNA damage in the colonic mucosa, assessed using the microgel electrophoresis (‘Comet’) assay was lower in the CrystaLean-fed group than in the rats fed sucrose or maize starch. DNA damage is considered to play a crucial role in the initiation and development of colon cancer. Acknowledgements: This study was funded by the EU (project numbers AIR2-CT94-0933 and AIR-2-CT94-7122)
Session 7, Resistant starch: A food ingredient with significant physiological and health benefits
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