The journal Nature Communications recently published the results of a randomized, controlled dietary intervention evaluating the effects and mechanisms by which oats affect cholesterol levels in people with metabolic syndrome. Comprised of two separate 1:1 controlled interventions, they evaluated the effect of a short-term high-dose oat diet, during which participants had two days of three oat meals per day (100g rolled oat flakes as a porridge with each meal), as well as the effects of longer-term moderate oat diet, a six week dietary intervention of one oat meal per day (80 g oat flakes), with each dietary intervention compared to an appropriate control oat-free diet group. Both groups had a 6-week follow-up period, so any lasting effects of the high-dose oat group could also be determined.
The primary outcome was the plasma concentration of dihydroferulic acid (DHFA), a microbial derivative of the phenolic compound ferulic acid, with many secondary outcomes (various glycemic analytes, lipids, kidney and liver function, etc.). The high-dose diet appeared to result in more significant changes than its control group, including a 10% reduction in LDL cholesterol, an 8% decrease in total cholesterol, and a significant increase in DHFA. In contrast, the 6-week moderate-dose oat diet did not significantly improve lipids or increase DHFA, though it did increase ferulic acid levels. A number of other findings were reported, including an increase in Erysipelotrichaceae UCG-003 levels in the high-dose group, a genus previously associated with healthy aging, and which may have been responsible for the metabolism of ferulic acid to DHFA. Overall, this study strongly suggests that the microbial metabolism of oats may be responsible for their cholesterol-lowering properties, and that a short-term high-dose regimen may be more effective than a longer-term moderate-dose regimen.