While you’d be hard-pressed to find anyone who doesn’t think polyphenols are healthy for you, one of the lesser-known benefits of consuming a diet high in polyphenols is its beneficial impact on your gut bacteria.
There are certain substances that have a very significant impact on our gut bacteria balance, like probiotics for example, but other foods and beverages have a smaller, more moderate beneficial effect on our microbiota. Even though these effects are mild, consuming foods and beverages that have beneficial effects on a regular basis is one of the keys to good gut health. Polyphenol-rich foods are excellent to include as part of your overall gut-healing plan along with some of the other heavy-hitters like probiotics and prebiotics. Why? Let’s break it down.
What are Polyphenols?
Polyphenols are naturally-occurring compounds found in in plants. Many of these plants make up our food supply, including fruits, vegetables, coffee, tea, and wine. Once consumed, only about 5-10% of polyphenols are directly absorbed in the small intestine, while the rest make their way to the colon to be broken down by our gut bacteria into metabolites, which then exert their important physiological effects. (1) Researchers are now discovering that the relationship between polyphenols and the gut microbiota is a two way street: that is, the polyphenols change the composition of the gut bacteria, and the gut bacteria are responsible for metabolizing the polyphenols into their bioactive metabolites.
Polyphenols Increase Good Bacteria and Decrease Bad Bacteria
The gut contains over 100 trillion bacteria (that’s ten times the amount of bacteria than we have human cells!) that play a vital role in our overall health. (2) These bacteria are negatively altered by antibiotics, stress, the food we eat, and more, eventually leading to a problem called dysbiosis. Dysbiosis is an imbalance of bacteria that can occur in any of our mucus membranes, such as in the lungs, mouth, nose, and of course, the gut. (3) We’ll be focusing on gut dysbiosis in this article, as it’s something we definitely want to avoid or fix if we’re suffering from digestive problems. Dysbiosis is probably much more common than you’d think: it’s often seen in those with inflammatory bowel disease, fatty liver, obesity, colon cancer, IBS, and more. (4, 5, 6, 7, 8) One of the best things we can do for our digestive (and overall) health is balance our gut bacteria. Luckily, there are plenty of ways for us to do that and consuming polyphenols is one of them!
Polyphenols seem to act as a prebiotic-type substance, meaning that they increase the amount of healthy bacteria in the gut, such as Lactobacillus and Bifidobacteria strains. Tea is possibly the most researched out of all the high-polyphenol foods, with many studies proving the prebiotic effects of tea extracts, leaves and polyphenol compounds. (9, 10, 11, 12, 13) Compared to those not treated with polyphenols, rats consuming red wine polyphenols have completely different predominant bacteria: those not consuming polyphenols showed predominantely Bacteroides, Clostridium and Propionibacterium species, while polyphenol-treated rats had mostly Bacteroides, Lactobacillus and Bifidobacterium species, showing that polyphenol intake can make quite an impact on gut bacteria. (14) In a study on humans, a wild blueberry drink significantly increases Lactobacillus counts. (15) Here’s the best news you’ll hear today: red wine also contains polyphenols that seem to have a similarly beneficial impact on gut bacteria. (16) Pretty sure that sentence made this article worth reading, didn’t it? It gets even better: cocoa also has prebiotic activity. (17) While this article isn’t meant to give you an excuse to go on a wine and chocolate free-for-all, it does mean that consuming these foods in moderation is likely beneficial for your gut flora.
Not only do polyphenols increase counts of beneficial bacteria, they also inhibit growth of potentially pathogenic bacteria. Catechin, a polyphenol found in tea, chocolate, apples, and blackberries (to name a few), has been shown to significantly inhibit proliferation of Clostridium histolyticum, a pathogenic bacteria. (18) Phenolic compounds contained in various berries have also been studied, showing antimicrobial effects on human pathogens such as Staphylococcus and Salmonella. (19) Studies also show that tea phenolics consumption repress the growth of Clostridium perfringens, Clostridium difficile, and Bacteroides spp. (20)
Include Polyphenol-Rich Foods for Balanced Gut Flora
By now you understand that it’s not just probiotics that can make a big difference in the balance of your gut bacteria. Eating polyphenol-rich foods on a regular basis, along with probiotics, prebiotics, and resistant starch will balance your microbiotia and get you on your way to good gut health! You will of course want to exclude any polyphenol-rich foods that you are sensitive to, but otherwise include as many as you’d like! There’s more research to be done in this area, and we don’t know all the ways that each different polyphenol affects us, so it’s best to consume a variety of polyphenol-rich foods for the best results. To get you started, below is a list of the Top 40 Paleo Polyphenol-Rich Foods from highest in polyphenols to lowest per serving. (21) Note that not all foods have been tested for their polyphenol content, so this list only includes those that have been studied. You can check out the polyphenol content of a food here, in case you’re wondering about one not on the list!
Top 40 Polyphenol-Rich Foods:
- Black elderberry
- Black chokeberry
- Black currant
- Globe artichoke heads
- Sweet cherry
- Flaxseed meal
- Dark chocolate
- Black tea
- Green tea
- Red wine
- Black grape
- Black olive
- Red currant
- Green olive
- Red onion
- Green grape
- Red chicory
- Yellow onion
- White wine
This is a guest post written by Kelsey Marksteiner, RD. Kelsey is a Registered Dietitian with a Bachelors degree in Nutrition from NYU and a Master’s in Human Nutrition and Functional Medicine. She works in private practice and recommends individualized dietary therapy focusing on biologically appropriate diet principles to aid her clients in losing weight, gaining energy, and pursuing continued health. She is a firm believer that everyone is different, and she tailors her plan for each and every individual. Through her work, she aims to meld the dietary wisdom of traditional cultures with the latest science in integrative and functional medicine to create plans for her clients that work in the modern world. You can learn more about Kelsey on her staff bio page, or by visiting her private practice website. Join her newsletter here!
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