Today we’re talking all things polyphenols! Here’s a little summary of what we’re getting into:
The Big Idea
- Humans and plants co-evolved to help each other survive, and polyphenols were integral for nurturing this relationship. Even though they aren’t considered “essential nutrients,” the latest research is starting to suggest otherwise.
- Polyphenols help prevent disease by interacting with our DNA and modulating our gut microbiome—they are not just antioxidants as we once thought.
Why It’s Important
- Our hunter-gatherer ancestors ate a much wider variety of plant foods, primarily because they had to adapt to the seasons. Today, 15 crops make up 90 percent of the Standard American Diet (which unfortunately is being exported all around the word).
- Eating a diversity of plant foods helps diversify our gut microbiome, which is linked to better health, less chronic disease, and greater resilience for our bodies and minds.
- There are over 8,000 different polyphenols identified to date, and each one has a unique effect on our biology. Most people aren’t getting enough of these powerful plant compounds because our diets are so limited today. It might sound basic, but eating a variety of plant foods is one of the best and simplest ways to reap the healing benefits of polyphenols.
Try This: A Deep Dive Into The Healing Power Of Polyphenols
There are over 25,000 different phytochemicals, 8,000 different polyphenols, and 30,000 edible plant species worldwide (1)(2)(3).
As we mentioned above, our hunter-gatherer ancestors naturally ate a much wider variety of plants primarily because they had to. However, today, three crops makeup ⅔ of our calories in the United States (and increasingly globally)…wheat, corn, and soy 🤯(4).
That means we’re missing out on all the amazing anti-inflammatory, anti-aging, disease-fighting benefits polyphenols have to offer. Each polyphenol has a slightly different structure, which means it has a slightly different function and impact on our bodies, which is why it’s so important to eat a diversity of plant foods to get as many benefits from these molecules as we can.
But the world of polyphenols can be complex and confusing, so today we’re going to break it down so we can really get excited about how freaking awesome they are and hopefully you can start incorporating more into your diet!
In this newsletter, I’m going to give you the full breakdown of what polyphenols do for our gut health, and overall health, and how to incorporate eating more in your life in ways that align with everything we’ve talked about in previous newsletters on blood sugar and metabolic health.
But first, let’s go on the journey of how the human and plant relationship came to be.
What Are Polyphenols? An Evolutionary Perspective
Plants needed to protect themselves against threats like ultraviolet radiation and disease. Especially after the arrival of insects, herbivores, and our early human ancestors, plants had to start fighting back so they could survive and pass their genes onto the next generation (5).
Phytochemicals are plants’ main line of defense and survival. Most concentrated in the stems, leaves, and seeds, phytochemicals are a survival mechanism for the plant—they don’t want to be eaten just as much as we don’t want to be eaten (more on this next).
But fruit sends a different message: it actually wants to be eaten. Why would plants want to be eaten? To spread their seeds! Plants make themselves irresistibly sweet, nutritious, and delicious. Using their polyphenols to project color, their predators can’t help but see and want to eat them. They are master manipulators that use predators to carry and plant their seedlings into a nice dollop of fresh “fertilizer.”
Fascinatingly, meats from herbivores have more polyphenols in their nutrient makeup. For example, pasture-raised beef from cows allowed to graze on plants and grasses contains significantly more polyphenols than beef from those fed a conventional diet of feedlot grains (6). This means that the meat our hunter-gatherer ancestors ate also contributed to their total polyphenol intake.
Polyphenols have incredible benefits for our biology through their ability to modulate our gene expression and gut microbiome to produce anti-inflammatory metabolites that lower inflammation, promote health, and prevent disease (7).
My friend and business partner Dr. Mark Hyman calls this relationship between plants and animals “symbiotic phytoadaptation,” which basically means certain plants co-evolved with humans to help each other survive. However, some plants want no business being eaten, and they make their phytochemicals extra toxic to make that loud and clear.
Which Plants Contain Toxic Phytochemicals?
It’s not all rainbows and butterflies, though. Nature didn’t exactly design phytochemicals with our well-being in mind, at least not in the beginning. Because plants can’t run away and don’t have claws, some make their phytochemicals extra potent as a way to discourage animals from eating them.
It’s good to be aware of the plants that could potentially cause issues, especially if you or someone you know has a sensitive gut or autoimmune condition. However, it’s worth mentioning that these phytochemicals aren’t problematic for everyone. As always, it’s all about personalization.
Here are a few of the main ones:
Nightshades (i.e. tomatoes, eggplant, peppers, potatoes, tomatillos, goji berries, and tobacco leaves) contain solanine, a phytochemical that can have irritating effects on the body for some people who might be more sensitive. They also contain lectins, which are most concentrated in the seeds but are also present in stems, leaves, and roots. My friend Dr. Gundry is one of the go to experts on this topic.
Lectins are the highest in legumes (cashews, beans, peanuts, lentils, peas, soybeans), grains, and certain nuts and seeds (8)(9)(10). As mentioned above, small doses are tolerated and safe for most humans. But some people are more sensitive than others (including me, my face gets red and flush when I eat too many nightshades, and my digestion feels totally off when I have a lot of cashews and other high-lectin foods).
If you think you might be sensitive to lectins, try eliminating them altogether and then adding them back one at a time to see which foods you’re most sensitive to (that’s how I found out about my sensitivities).
Lectins are a highly-debated topic with many experts saying that it’s overblown and that our body creates its own lectins. I first learned about this from Dr. William Li in our interview together. So, are lectins the devil? Probably not. But do some people, especially with sensitive guts or autoimmunity, do better by limiting them? It seems so.
“Anti-nutrients” are another potentially problematic plant molecule that binds to calcium, magnesium, and other minerals, making them difficult for predators to absorb and use. Some examples of these include oxalates (high in spinach, kale, beets) and phytates (high in nuts, seeds) (11).
To reduce the anti-nutrient and lectin content of plant foods, you can cook, pressure cook, peel, de-seed, sprout, and ferment high-lectin foods, too (11). Anti-nutrients are in almost every plant food, so cutting them out means we’d be missing out on all of their incredible polyphenols and nutrition.
The Different Type Of Polyphenols
Flavonoids are the largest group of polyphenols. They are present in over 4,000 plant species and have antimicrobial, anti-inflammatory, and neuroprotective properties. DNA methylation, targeting genes to turn off cancer cell proliferation, and killing zombie cells are other ways they work.
Insulin sensitivity, cholesterol, and blood sugar are all positively impacted by polyphenols (2)(5), which lowers our risk for chronic diseases like obesity, heart disease, Alzheimer’s, cancer, and type 2 diabetes (12)(13).
In the landmark Nurses’ Health Study, a 20-year study of over 200,000 health professionals, found that those who ate more anthocyanin-containing foods had a 15% lower risk of type 2 diabetes. In particular, two or more servings of blueberries per week was associated with a 23% lower risk; and five or more servings of apples and pears was associated with a 23% lower risk (14).
That’s one example of how one polyphenol (like anthocyanin) can be present in multiple fruits and exhibit the same beneficial outcome. There are literally thousands of different flavonoids in the plant kingdom, which emphasizes the importance of eating a diversity of plant foods to get all the benefits of their polyphenols.
Here are a few of the main flavonoid and non-flavanoid polyphenols, their active metabolites, and a list of foods that contain them. (Hint: look for the foods that are mentioned more than once—those are the ones you’re going to want to eat more of!)
Anthocyanins– these are your purple, blue, and black plant foods. They include blueberries, blackberries, raspberries, cranberries, cherries, plums, red grapes, red cabbage, cinnamon, cocoa, colorful rice, and purple sweet potatoes (15)(16).
Flavonols- quercetin (onions, garlic, chili pepper, apples, asparagus, broccoli, oregano), kaempferol (spinach, kale, dill, chives, tarragon), and fisetin (strawberries, persimmons, apples, onions, cucumbers) (16)(17)(18)(19).
A note about quercetin: It has been in the research a ton for its immune-supporting (anti-cancer, anti-aging) properties. This is definitely one I would make a priority in my life.
Flavones- apigenin and luteolin (celery, parsley, thyme, dandelion, chamomile, carrots, olive oil, peppermint, rosemary, oregano) (18)(20).
Flavanones- naringenin and hesperidin (lemons, limes, grapefruit, cherries, oranges, tomatoes)(18)(21).
Flavan-3-ols- catechins, epicatechins, gallocatechin, epigallocatechin, and tannins. Most known for their abundance in green tea, these are also present in black tea, apples, bananas, blueberries, peaches, pears, strawberries, and cocoa (16)(18)(22).
Isoflavones- genistein and daidzein are two of the main ones in legumes, specifically soybeans and tofu, and are commonly referred to as phytoestrogens, due to their estrogen-like activity in the body (18).
Phenolic acids- these include benzoic acid, cinnamic acid, and their derivatives: gallic acid, caffeic acid, chlorogenic acid, and ferulic acid. Present in coffee, blueberries, olive oil, kiwi, plums, apples, cherries, red wine, and cereal grains like wheat, rice, and oats (20).
Stilbenoids- resveratrol (grape skins, red wine, peanuts, blueberries, and cranberries).
Lignans- sesame seeds and sesame oil, flax seeds and flax oil, olive oil, cashews, peanuts, grapefruit, tangerine, lemon, apricot, peach, plum, pears, and nectarines (23).
Polyphenols Help Us Grow The Good
Polyphenols feed our good gut bugs and help them grow. Just like indigestible plant fibers feed Lactobacillus, Bifidobacterium, and Akkermansia that work to help keep our gut barrier strong, so do polyphenols.
Many different factors we are exposed to daily negatively impact our gut microbiome. NSAIDs, antibiotics, sugar, poor diet, food sensitivities, heavy metals, omega-6 seed oils, stress, and exposure to toxic chemicals disrupt our gut microbiome. Over time, these wipe out our good bacteria and let the bad ones take over, which leads to dysbiosis, inflammation, and a leaky gut.
Polyphenols can be a fantastic way to support a healthy gut and prevent diseases that are rooted in gut dysfunction (spoiler alert: it’s damn near all of them). One of the benefits is producing short-chain fatty acids like butyrate, which fuels our intestinal cells and keeps our gut barrier strong.
The MaPLE trial, a randomized controlled trial in adults ages 60 and older with high zonulin levels (a marker of leaky gut), demonstrated the gut-strengthening effect of a polyphenol-rich diet. For eight weeks, the study participants were given a polyphenol-rich diet that included three polyphenol-rich snacks per day (24).
Here were the snacks that were included in the study: 120g of blueberries (that’s about ¾ cup), 200mL of blood orange juice (about 1 cup), 110g of blood orange fruit (one orange), 125mL of pomegranate juice (½ cup), 200mL of green tea (about 1 cup), 100g of Renetta apple purée (about ½ cup), 150g Renetta apple (one apple), 10g of dark chocolate chips (about ⅛ cup), or 2g of cocoa (about 3 tablespoons) for an average of 724 mg of polyphenols per day.
Compared to controls, the polyphenols from cocoa and green tea increased butyrate-producing bacteria and reduced zonulin, which means less leaky gut. Other polyphenols reduced harmful methane-producing bacteria and lipopolysaccharide-producing bacteria that cause endotoxemia and chronic inflammation (science direct, Maple Trial). In addition to improving gut microbiome composition, the polyphenol-rich diet also lowered inflammatory cytokines, the most powerful driver of inflamm-aging.
What Does This Mean For Me?
As we get older, modern-day life takes a toll on our gut (where most chronic diseases begin). Eating polyphenol-rich foods could be a way to prevent, or delay that from happening. Some polyphenol metabolites have anti-inflammatory, neuroprotective properties because they can cross the blood-brain barrier (5).
Curcumin, for example, the polyphenol in turmeric provides a lot of its anti-inflammatory action by restoring gut dysbiosis which indirectly impacts the brain through the gut-brain axis (25). And ellagic acid, a polyphenol in cranberries and pomegranate seeds, feeds Akkermansia muciniphila (26). This gut microbe modulates the thickness of our intestinal mucosal layer and keeps food and bacteria from slipping through intestinal cells and making their way into circulation (27).
Polyphenol expert and a friend of mine, Dr. William Li, has been on my podcast before to talk about why it’s important to have Akkermansia in our gut. It’s associated with decreased inflammation, the ability to combat obesity, and anti-tumor responses to some types of cancer immunotherapy.
In my Protocol for this week, I’m going to give you some practical tips for increasing your intake of polyphenol-rich foods, and how I include a diversity of them in my diet in a way that honors everything we’ve learned about blood sugar.
I. Eat fruit after dinner: Fruits are an incredible source of polyphenols. However, we can’t avoid the fact that a lot of fruits are pretty high in sugar, especially higher glycemic fruits, smoothies, and juices. Instead of eating fruit in the morning, by itself and on an empty stomach, I typically eat my fruit after I’ve had a nice meal rich in quality protein and healthy fats.
- Berries with dark chocolate. If you’re a fan of dark chocolate like me, this combo is unreal for your taste buds and super satisfying as a post-meal sweet treat. You can have it after dinner, or any meal you prefer. Plus, you’re getting the amazing catechins and anthocyanins from the cocoa in dark chocolate. Shoot for 70% cocoa or higher.
II. Drink high-quality tea.Drinking herbal tea is a great way to get in a variety of polyphenols. There are over thousands of research papers on the power of the catechins found in green tea for example!
Coffee is another amazing source of polyphenols. Studies from all over the world have shown that black coffee is the most significant source of antioxidants in our diet, but we don’t want it to be the only one (19)(20)!
My go-to teas are matcha, green tea, or turmeric tea. These teas are incredibly rich in polyphenols, but we have to be careful because tea can also be a significant pesticide, heavy metal, and microplastic exposure source. If you drink tea daily or throughout the day, chose a clean option.
Here’s what I look out for when buying high-quality teas:
- Certified organic. This guarantees no pesticides or toxic agrochemicals. I know organic costs more money, but every time you vote with your dollar to support organic foods, it increases their demand. Over time, this can result in more organic products being available and accessible.
- Natural Fiber Tea Bags. Tea bags release up to 11.6 billion microplastics in a single cup (30)—insane, right? Use organic loose leaf tea instead and steep it using a stainless steel or glass strainer. If you like tea bags for their convenience or portability, look for the kind made from organic hemp, cotton, or plant fibers and free from bisphenol-A (BPA), phthalates, polypropylene, and epichlorohydrin.
III. Challenge yourself to pick out a “weird” fruit or vegetable. If you don’t have food sensitivities or intolerances, this can be a fun way to get benefits from different polyphenols you and your gut bacteria may have never experienced before. Think of all of the colorful plant foods you see in the supermarket and the hundreds of plants we could eat. I challenge you to buy some vegetables you usually don’t the next time you go to the grocery store.
Have you ever tried jicama? This root vegetable is all the rage because it’s low in sugar, making it a fantastic low glycemic substitute. Here’s a simple recipe for jicama fries.
What about cherimoya? You can get that from a lot of Asian food markets. There are also subscription services like miamifruit.org that ship weird and different fruit and veggie boxes to your home.
The relationship between plants and animals is fascinating. Plants probably didn’t evolve to produce phytochemicals for our benefit. However, evolution has made it so that many of them work in favor of us and our gut bacteria. In return for housing and feeding our gut bacteria high-quality polyphenols, they pay us back by producing metabolites that have incredible anti-inflammatory, anti-cancer, neuroprotective, disease-fighting benefits that keep us healthy and strong.
Yes, some people are more sensitive to the more “toxic” phytochemicals and anti-nutrients in plant foods. But as long as we personalize our diets, and of course focus on healing our guts, we can ensure that we take advantage of all the great things that polyphenols have to offer.
Regularly switching it up and eating different plant foods means we are diversifying our gut ecosystem, which makes us all-around healthier, happier, and more resilient.