Polyphenols are bioactive compounds found in fruits, vegetables, seeds, coffee, and cocoa. They have been shown to support human health in many ways, including the body’s response to oxidative stress and inflammation. An estimated 90% of dietary polyphenols are not digested in the small intestine and may therefore influence microbiota in the colon. Recent research has explored the potential role of polyphenols in support of gut microbiome health. 

Resveratrol (trans-3,4’,5 trihydroxystilbene) is a polyphenol called a stilbenoid that is found in grape skin, berries (such as blueberries and raspberries), and peanuts. Resveratrol is known for its role in supporting a healthy response to oxidative stress and inflammation and its support of cardiovascular and metabolic functions within the human body. It has also been shown in studies to influence the integrity of the gut microbiome. 

A recently published review article explored the potential impact of resveratrol and other micronutrients on parameters related to inflammatory bowel disease. Supplementation with resveratrol was shown in animal studies to increase the abundance of the beneficial bacteria Bifidobacterium and Lactobacillus, which the authors conclude may have contributed to the restoration of colonic barriers in the presence of colitis. Another animal study reported that relief in colitis symptoms while supplementing with resveratrol may be attributed to observed improvements in microbial dysbiosis and inflammatory markers, including interleukin (IL)-6 and IL-17. 

Resveratrol has also been shown to influence the Firmicutes-to-Bacteroidetes (F/B) ratio. Higher F/B ratios have been linked to increases in the occurrence of certain diseases. Resveratrol and other stilbenoids have been shown in studies to decrease the relative abundance of Firmicutes, resulting in decreases in the F/B ratio. 

Animal studies have also indicated that resveratrol may influence the population of short-chain fatty acid (SCFA)-producing bacteria. One study involving supplementation with resveratrol for 8 weeks reported increases in Lachnospiraceae, Blautia, and Dorea populations, which are known to produce butyrate, an SCFA found to support many aspects of human health.

Clinical studies suggest that polyphenols may support gut microbial health. One clinical study reported increases in certain species of Bifidobacterium and decreases in certain harmful bacteria after supplementation with tea polyphenols. Another study involving green tea reported increases in the proportion of Bifidobacterium. 

A randomized, double-blind controlled, crossover study explored the efficacy of cocoa polyphenols on the gut microbiome. The study involved daily supplementation for 4 weeks. It reported significant increases in the populations of Bifidobacterium and Lactobacillus.  

Recent research has explored dietary influences, such as polyphenols, on the composition of the gut microbiome. Polyphenols may support microbial fermentation and the promotion of healthy microbial populations. 

By Colleen Ambrose, ND, MAT