The acute effects of inulin and resistant-starch on postprandial serum short-chain fatty acids and second-meal glycaemic response in lean and overweight humans

BACKGROUND/OBJECTIVES: Colonic-fermentation of dietary-fibre to short-chain fatty-acids (SCFA) may protect against obesity and diabetes, but excess production of colonic SCFA has been implicated in the promotion of obesity. We aimed to compare the effects of two fermentable-fibres on postprandial SCFA and second-meal glycaemic response in healthy overweight or obese (OWO) vs lean (LN) participants. METHODS: using a randomized cross-over design, 13 OWO and 12 LN overnight fasted participants were studied for 6h on 3 separate days after consuming 300mL water containing 75g glucose(GLU) as control or with 24g inulin(IN) or 28g resistant-starch(RS). A standard lunch was served 4h after the test-drink. RESULTS: Within the entire group, compared to control, IN significantly increased serum SCFA (p<0.001) but had no effect on FFA or second-meal glucose and insulin responses. In contrast, RS had no significant effect on SCFA but reduced FFA rebound (p<0.001) and second-meal glucose (p=0.002) and insulin responses (p=0.024). OWO had similar postprandial serum SCFA and glucose concentrations but significantly greater insulin and FFA than LN. However, the effects of IN and RS on SCFA, glucose, insulin and FFA responses were similar in LN and OWO. CONCLUSIONS: Resistant-starch has favorable second-meal effects, likely related to changes in FFA rather than SCFA concentrations. However, a longer study may be needed to demonstrate an effect of RS on SCFA. We found no evidence that acute increases in SCFA after IN reduce glycaemic responses in humans, and we were unable to detect a significant difference in SCFA responses between OWO vs LN subjects.