The acute effects of inulin and resistant starch on postprandial serum short-chain fatty acids and second-meal glycemic response in lean and overweight humans.
Level 2 - randomized trial
Individual randomized crossover trial in humans
PubMed 27966565 · doi:10.1038/ejcn.2016.248
What was done
In a randomized crossover design, 13 overweight or obese and 12 lean healthy participants were tested on three separate days after an overnight fast. Participants consumed a 300 ml drink containing 75 g glucose alone (control), 75 g glucose with 24 g inulin, or 75 g glucose with 28 g resistant starch. Blood was monitored over 6 hours, with a standard lunch served at 4 hours post-drink to measure serum short-chain fatty acids (SCFA), free fatty acids (FFA), and second-meal glucose and insulin responses.
What was found
Across all participants, inulin significantly increased serum SCFA compared with control (P<0.001) but showed no effect on FFA, second-meal glucose, or insulin responses. In contrast, resistant starch did not significantly affect serum SCFA, but significantly reduced FFA rebound (P<0.001), second-meal glucose response (P=0.002), and second-meal insulin response (P=0.024). Overweight/obese participants had higher baseline/postprandial insulin and FFA than lean participants, but both groups showed similar SCFA, glucose, insulin, and FFA responses to the fiber interventions.
Why it matters
This study challenges the assumption that acute elevations in circulating SCFA mediate the second-meal glycemic benefits of dietary fiber, indicating that resistant starch improves subsequent glycemic control through FFA suppression rather than rapid SCFA elevation.
Limits
The study had a small sample size (n=25 total) and evaluated only single-dose, acute 6-hour responses, which may be insufficient to capture slower fermentation kinetics of resistant starch. Exact baseline or postprandial absolute values and effect sizes for glucose, insulin, and SCFA concentrations were not reported in the abstract.
Cited by
- partial Soluble fermentable fiber serves as fuel for the gut microbiome and produces short-chain fatty acids like butyrate and propionate, which show positive metabolic health benefits in randomized controlled trials.