Dietary supplementation with β-glucan enriched oat bran increases faecal concentration of carboxylic acids in healthy subjects

Abstract

Carboxylic acids (CAs), especially butyric acid, have been suggested to counteract colonic diseases, such as ulcerative colitis and colon cancer. Colonic formation of CAs can be influenced by the diet, but the concentrations and pattern formed need to be evaluated for different food products in humans. To elucidate how the colonic concentration of CAs in healthy subjects is influenced by dietary supplementation with oat bran, and whether the concentration varies over time and during consecutive days. Twenty-five healthy subjects (age 24+/-1.3) were recruited to the study. The subjects were given 40 g beta-glucan enriched oat bran per day, corresponding to 20 g dietary fibre, in 4 slices of bread. CAs were analysed in faeces during three consecutive days after 0, 4, 8 and 12 weeks on this diet. The concentration of acetic, propionic, butyric, isobutyric and isovaleric acid was higher (P<0.05-0.001) after 8 weeks on the oat bran diet as compared with values at entry, whereas that of lactic acid was lower (P<0.05). After 12 weeks, the concentrations of acetic, propionic and isobutyric acid were still higher and that of lactic acid lower. The variation between individuals was considerable, whereas in the same individuals there was little variation. Oat bran increased the faecal concentration of CAs after 8 weeks, indicating an increased concentration also in the distal colon. The concentration of all main acids increased, except for lactic acid, which decreased. Oat bran may therefore have a preventive potential adjunct to colonic diseases.