Here, we show that supplementation with the commonly consumedflavonoid quercetin impacted gut microbiome composition and resulted in asignificant reduction in atherosclerosis burden in conventionally-raised (ConvR)Apolipoprotein E (ApoE) knockout (KO) micefed a high-MAC (microbiota-accessible carbohydrates) diet. The gene discussed is APOE; the disease is atherosclerosis.