Comparison between physiological effects of konjac-glucomannan and propionate in baboons fed 'Western' diets

Abstract

Dietary fiber and resistant starch are fermented by colonic bacteria to short-chain fatty acids (SCFA) such as acetic, butyric and propionic acid, which the colon absorbs. It has been suggested that the beneficial metabolic effects of dietary fiber may be mediated through propionate. We therefore compared the effects of a soluble dietary fiber concentrate, konjac-glucomannan (K-GM), and of propionate on plasma fibrinogen, serum and liver lipid, glucose tolerance, insulin response and liver glycogen in baboons. Twelve male baboons were fed a 'Western' diet with or without K-GM (5%) or sodium propionate (2%) supplements for periods of 9 wk in a crossover, randomized order, with stabilization periods in between. Measurements were taken at baseline and after 4 and 9 wk of each study period. After 9 wk, total serum cholesterol levels were significantly higher than pretest values when baboons consumed the unsupplemented Western diet (25%, p<0.05) or the propionate diet (17%, p<0.05). Konjac-glucomannan prevented this increase. The high density lipoprotein cholesterol concentration increased with all experimental diets (p<0.05). The percentage of total cholesterol as high density lipoprotein cholestero, was significantly higher with K-GM supplementation than with the other diets. Konjac-glucomannan supplementation also resulted in lower than baseline values for triglycerides (p<0.01) and circulating free fatty acids (p<0.05) after 9 wk. Only the propionate diet raised serum triglycerides significantly (by 6%) above baseline. Liver cholesterol concentration was 31-34% lower, and the area under the glucose tolerance curve was smaller with K-GM and propionate diets (p<0.05) than with the unsupplemented diet. We conclude that colonic production and absorption of SCFA (propionate) from soluble fiber may contribute to this fiber's metabolic effects.