If you choose blueberries or green tea for their polyphenols, here is a detail worth knowing. Only about 5% to 10% of polyphenols in monomeric and dimeric forms are absorbed in the small intestine. The rest reach the colon, where gut bacteria convert them into smaller phenolic acids and other metabolites. Those products can then enter the bloodstream.
This matters because the conversion is not uniform. A 2024 systematic review concluded that gut microbiota is a major contributor to inter-individual differences in polyphenol metabolism. A 2024 review in Food & Function described metabotypes, reproducible patterns of metabolite production, and noted that for many polyphenols these patterns remain poorly characterized. Two people can eat the same bowl of berries and produce different amounts and profiles of circulating metabolites.
So what does this mean at the table? Favor whole foods over concentrated products. Whole berries, tea, cocoa, and whole grains bring fiber and other compounds to the colon alongside polyphenols. Variety may be more useful than quantity, because different plant foods support different microbes. And pair polyphenol foods with fiber: a bowl of berries with yogurt and oats delivers both.
What the research points to is a shift in thinking. Specific foods are not nutrients to be dosed. They are substrates for a microbial community, and the most reliable way to support that community is a varied, fiber-rich, whole-food diet rather than a single anti-inflammatory ingredient.
