According to a study published in the journal Hypertension, researchers examined over 900 German subjects determining that higher intakes of total flavonoids, anthocyanins, polymers, and specifically proanthocyanidins were associated with statistically significantly lower systolic blood pressure (SBP) and pulse pressure (PP) and that higher intakes of berries and red wine were associated with higher microbial alpha diversity leading the researchers to conclude that up to 15% of the association between flavonoid-rich foods, including berries, red wine, and apples/pears, and SBP could be explained by the gut microbiome.