Unlocking the potential of polyphenols: Role of gut microbiota in modulating bioavailability and health effects of polyphenols
In this review, the important role of the gut microbiota in unlocking the bioavailability and health effects of dietary polyphenols is explored. It examines the dose-related activity of polyphenols, their biotransformation through the microbiota, their bioavailability, and the health effects of their metabolites, while also presenting a comparative overview of key studies in the field.
In humans, the bioactivity of polyphenols (bioactive compounds in red and white wine, olive oil, fruits, vegetables, etc. *) is highly dependent on the amount consumed and their interactions with the gastrointestinal tract and gut microbiota, which metabolize polyphenols into bioactive or inactive compounds. PolyphenolsPolyphenols are mainly phytochemicals found abundantly in natural plant food sources. The most impor... are generally absorbed to a limited extent in the small intestine due to their complex chemical forms. A significant proportion of polyphenols escapes absorption and reaches the colon, where the gut microbiota converts them into simpler phenolic metabolites. Such molecules are often more bioavailable than the original compounds and can enter blood circulation, leading to respective effects in the body. Although a higher polyphenol consumption has been associated with preventive and therapeutic outcomes, even low intake or poor intestinal absorption may still have benefits, since polyphenols in the colon can positively modulate gut microbiota composition and function, contributing to favourable shifts in the gut microbes. These interactions can influence metabolic, immune, and neurological pathways in the human body. Evidence from epidemiological and interventional studies suggests that higher polyphenol intake can be associated with favourable changes in biomarkers of oxidative stress, inflammation, endothelial function, and gut barrier integrity.
The authors emphasize the importance of integrating microbiome and polyphenol research to better understand the health benefits of dietary polyphenols and caution that, even though the current findings are promising, more robust clinical evidence is needed before drawing firm conclusions about the preventive or therapeutic efficacy of dietary polyphenols.
(*) For example:
- The average polyphenol intake in the Spanish Mediterranean Diet is 1171 mg/day: About 68% of the total dietary antioxidant capacity came from beverages (such as red wine), and 20% from fruits and vegetables
- In the PREDIMEDThe PREDIMED study is one of the few randomized controlled trials about the Mediterranean Diet. More... study: the average polyphenol intake was ~820 mg/day (443 mg flavonoids, 304 mg phenolic acids): Fruits’as primary source; flavanols mainly from red wine/apples; olive oil and olives provide ~11%.
