Propionate lowers blood glucose and alters lipid metabolism in healthy subjects

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Abstract
Incorporation of 3.3 g sodium propionate per 50 g available carbohydrate portion of bread reduced acutely the blood glucose response area in six healthy volunteers by 47.6 ± 12.4% (P < 0.02). Similarly, in vitro digestibility was reduced by 47.4 ± 1.1% (P < 0.01). One week of dietary supplementation with 9.9 g sodium propionate in bread/d reduced the blood glucose area in comparison with standard propionate-free bread by 38.0 ± 8.7% (P < 0.05), but increased fecal bulk by 28.3 ± 8.7% (P < 0.05) and anaerobic microflora by 0.564 ± 0.165 × 106/g feces (P < 0.05), specifically as bifidobacteria. Day-long breath hydrogen concentrations did not increase after 1 wk on propionate bread but methane production increased in the three methane producers. Although lipid changes were not significant, five subjects showed reduced high-density-lipoprotein and increased triglyceride concentrations, both of which correlated with increased fecal weight (P < 0.05). Because propionate reduces the rate of starch digestion, studies using oral propionate must take into account its action as an enzyme inhibitor.