EFFECT OF HIGH-AMYLOSE STARCH AND OAT BRAN ON METABOLIC VARIABLES ANDBOWEL FUNCTION IN SUBJECTS WITH HYPERTRIGLYCERIDEMIA

We compared the effects of a diet in which approximate to 25% of the c arbohydrate was replaced by high-amylose starch with those of a simila r diet high in oat bran or low-amylose starch in 23 hypertriglyceridem ic subjects who were overweight mostly because of abdominal adiposity. Each diet was consumed for 4 wk in random order and in a crossover fa shion. Overall, the diets were high in carbohydrate (> 55% of energy) and low in fat (< 30% of energy); the amount of resistant starch in th e foods containing high-amylose starch was 17 g in women and 25 g in m en. The metabolic effects of specific starches on plasma lipids, fasti ng and postprandial glucose and insulin profiles, and bowel function w ere assessed at the end of each intervention. Plasma triacylglycerols (triglycerides) were significantly lower after the oat bran diet than after the other two diets (P < 0.02). No other effects on fasting plas ma lipids, glucose, or insulin were noted. However, when the high-amyl ose starch comprised 33% of the carbohydrate content in a test meal, t here was a significant but biologically small reduction in the overall postprandial plasma insulin concentration by 17% relative to the low- amylose diet (P < 0.01). Both the oat bran and the high-amylose diet r esulted in an increased frequency of bowel actions and lower fecal pH (P < 0.02) relative to the low-amylose diet. However, unlike the oat b ran diet, the high-amylose diet increased short-chain fatty acid conce ntrations in fecal water by 32% (P < 0.001).