Fermentation of dietary starch in humans.
OBJECTIVE
Dietary starch that escapes digestion in the small intestine may be quantitatively more important than dietary fiber as a substrate for fermentation. The products of fermentation have important implications in the pathogenesis of colorectal cancer and other diseases of the large bowel, which are uncommon in Africans but have a high prevalence in Western populations.


METHODS
Maize porridge is a staple of most blacks in South Africa. Stale maize porridge (high-resistant starch [HRS]) seems to induce greater fermentation in the large bowel than fresh maize porridge (low-resistant starch [LRS]).


RESULTS
In the present study, healthy colostomy subjects fed stale maize porridge had significantly more production of short-chain fatty acids (SCFA) (mean SCFA, HRS = 182.6; mean SCFA, LRS = 116.1; p < 0.05) in their colostomy effluent together with a significant drop in stool pH (mean pH, HRS = 5.91; mean pH, LRS = 6.70; p < 0.001). The SCFA butyrate (mean, HRS = 35.1; mean, LRS = 17.6; p < 0.05) and acetate (mean, HRS = 93.9; mean, LRS = 65.8; p < 0.05) were significantly elevated on the stale maize porridge diet when compared with consumption of fresh maize porridge. SCFA propionate (mean, HRS = 43.1; mean, LRS = 24.8; p = 0.05), also increased with stale maize porridge, but was not statistically significant.


CONCLUSIONS
A high-resistant starch diet and its resultant increase in fermentation products may be partly responsible for protecting the black population against colorectal cancers and other large bowel diseases.
Ahmed
R
R
Gastroenterology Division, Chris Hani Baragwanath Hospital, Soweto, South Africa.
Segal
I
I
Hassan
H
H
D019342:Acetic Acid / Q000378:metabolism; D000328:Adult; D044383:Black People; D002087:Butyrates / Q000378:metabolism; D015179:Colorectal Neoplasms / Q000517:prevention & control; D003125:Colostomy; D004040:Dietary Carbohydrates / Q000378:metabolism*; D005232:Fatty Acids, Volatile / Q000378:metabolism; D005285:Fermentation; D005772:Gastrointestinal Transit / Q000502:physiology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007413:Intestinal Mucosa / Q000378:metabolism; D008297:Male; D012307:Risk Factors; D013019:South Africa; D003313:Zea mays / Q000378:metabolism*
D002087:Butyrates; D004040:Dietary Carbohydrates; D005232:Fatty Acids, Volatile; D019342:Acetic Acid