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.
Certain substances 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?
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) 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. (13) In a study on humans, a wild blueberry drink significantly increases Lactobacillus counts. (14) 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. (15) Pretty sure that sentence made this article worth reading, didn’t it? It gets even better: cocoa also has prebiotic activity. (16) 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. (17) Phenolic compounds contained in various berries have also been studied, showing antimicrobial effects on human pathogens such as Staphylococcus and Salmonella. (18) Studies also show that tea phenolics consumption repress the growth of Clostridium perfringens, Clostridium difficile, and Bacteroides spp. (19)
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Include Polyphenol-Rich Foods for Balanced Gut Flora
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. (20) 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
- Blueberry
- Globe artichoke heads
- Coffee
- Sweet cherry
- Strawberry
- Blackberry
- Plum
- Raspberry
- Flaxseed meal
- Dark chocolate
- Chestnut
- Black tea
- Green tea
- Apple
- Hazelnut
- Red wine
- Black grape
- Black olive
- Spinach
- Pecan
- Prune
- Red currant
- Peach
- Green olive
- Red onion
- Green grape
- Potato
- Shallot
- Red chicory
- Broccoli
- Nectarine
- Pear
- Yellow onion
- Apricot
- Asparagus
- Almond
- White wine
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The article monitors cocoa. I read recently that cocoa is processed and is mostly stripped of its nutritional benefits. Cacao is the preferred ingredient for health. Do you agree?
I read about the anti-pathogenic activity of raspberry seed powder taken orally, and surfed in trying to find out if the powder could be taken without damaging good microbes like the friendly gut bacteria. And if the raspberry seed powder really can knock out bad bacteria and foster the good — how does it do that??
Well it seems like a jump to say that since polyphenols are in wine etc that then wine is ok when alcohol is a sugar e.g.
What about turmeric (curcumin)?
Great article (thanks guys). What really needs to be mentioned (and hasn’t been) is that wild plants have higher phenolic content than their corresponding cultivated plants. This is confirmed in many different studies. Therefore, if you want to receive the most polyphenols, you should strive to eat wild-gathered foods (rather than cultivated foods). This is not to say that organic produce isn’t healthful, but wild plants have a deeper nutrition (again, that comment can be supported by study) and have intact phytochemistry (i.e., it hasn’t been bred out of them), resulting in more polyphenols, which in addition to the benefits to gut bacteria, provide higher antioxidant values.
I realize that most people are consuming store-purchased foods and, therefore, a general focus is placed on cultivated produce by most authors. However, this has created a general ignorance (I don’t mean for that to sound rude) of the value of wild plants and why people should learn to forage or otherwise secure wild plants in their diets (when possible). After all, humans have consumed exclusively wild plants for most of their existence. Best wishes.
A warning about flax seed – it isn’t often mentioned, but it is thyroid suppressing (google it). I have noticed this whenever I use it – I don’t feel very well afterwards at all.
Our gut is as unique as our finger print, most of us know that pre/probiotics benefit our gut, but few realize that polyphenols also benefit the healthy flora of our gastrointestinal system. Very good information here and thanks for sharing.
Question: Are frozen fruits as high as fresh in polyphenols (organic frozen) ? What about dried elderberries? The local beer and wine shop sells dried (or possibly freeze dried) elderberries that I’ve been wanting to re-hydrate to cook into a syrup. Is this ok or should I look for a different source? When I was growing up we had a huge elderberry bush (vine?) next to my uncle’s farm that my mom would make elderberry pie from-so good! Unfortunately, the county road crews came through and sprayed to kill it all-what a waste!
Thanks for the article Kelsey!
I have hypoglycemia, early morning insomnia and some adrenal fatigue. I’m wondering why i’m very sensitive to many nutrients. For example i lose sleep the following night if i consume chocolate at any point of day, probiotics, hcl, salt, avocados, sweet potatoes, salmon, alcohol. And all the supplements that affect the brain or adrenals (C,B,licorice,adaptogens,some amino acids) have very strong effects even with small doses.
My gut functions normally but i suspect some bacterial imbalance. Might the sensitivity be caused by leaky gut or leaky blood brain barrier?
This could be nervous system based, perhaps? The gut and brain definitely interact, but if you have AF and hypos it sounds like your mind is under a lot of stress. Perhaps accupuncture, meditation, breathing techniques might be helpful?
I have similar issues, and having accupuncture recently really helped me!
@danjon and Jamal
This is complex question. The short answer is that it depends on the polyphenol in question. As you may know, there are 1,000s of molecules with a polyphenolic chemical structure, with 100s identified in edible plants.
Let’s look at isoflavones as an example. These are flavonoids which are structurally similar to estrogens (FYI: can bind to the estrogen receptor…important in women). They are mainly found in soya products. They come in various conjugated forms: aglycone, plus various glucosides. Some in the latter class are very sensitive to heat and can be modified to their glycoside derivatives. The fermentation of certain foods during processing (e.g., tempeh or miso) results in the conversion of the glycoside to the aglycone forms. These aglycone forms are highly resistant to heat.
Flavonols (another class ) are present monomeric (e.g., catechins) or complex polymeric form (proanthocyanidins). They can be found in wine, but are highest in tea and chocolate. Compared to flavonoids above, flavanols are not glycosylated in foods and can be remarkably stable in heat (as long as the pH is acidic).
So, to make a long (and complex) story short, the answer is: It depends. My opinion is not to worry about it too much. Eat a variety and diverse source of fruits and veggies and let your gut flora and biology figure out the rest. You’ll be fine.
Happy eating,
Robert
I’m still trying to get my head around the fact that there are ten fold more life forms living within and on our own singular form. We are totally out numbered in this universe and completely dependent, but since we have a thinking brain we think we are special and superior. We may be nothing but a constillation or amalgam of organisms collecsed by conscienceness.
Could a moderate amount of red wine still have a beneficial impact for someone who has dysbiosis and or digestion problems? Or should they fix any gut related problems before reintroducing red wine?
I heard someone say alcohol could be detrimental for gut bacteria. I am not sure what type or amount of alcohol they were referring to, or if they were referring only to people with compromised gut health to begin with.
Thanks
Is this different from the bacteria that potato starch is supposed to feed, or are they the same? Should I drop one for the other, or do them both?
I read somewhere that processing involved in chocolate making destroys, or significantly reduces, polyphenols that were originally present. Is this true? Also, are there any cooking methods that have more adverse effect than others, and is the chemical integrity of polyphenols affected by the presence or absence of other common ingredients such as sugar, oil or lemon juice?
I was wondering about the same – do they get destroyed by heat (like enzymes) when you cook the food?
OK, no red wine, coffee, and chocolate binges. But perhaps a little less guilt about moderate use of these foods is in order. But how about a blueberry, artichoke, pecan, etc. free-for-all ;-)? I was amazed to see how many of the foods/drinks I love and eat often are in the top 40. Maybe that’s why I enjoy excellent digestive health 99+% of the time.