An apple a day may not totally keep the doctor away, but perhaps an apple, onion, banana, cabbage and some red wine might.
Many of the plant-based foods you eat every day have powerful substances in them called polyphenols. Polyphenols — part of the big group called phytochemicals — are natural compounds found in plants that boast important health benefits.
Just like a balanced diet helps you get all the nutrients you need, it can also help you get a healthy mix of polyphenols. So make sure to keep variety in your diet for the biggest benefit.
How Polyphenols Work and Their Health Perks
Believe it or not, the main purpose of plant polyphenols is to protect the plant against damage and pathogens, according to UC Davis Integrative Medicine. And it just so happens that humans gain the same benefits when we eat the plants.
Polyphenols are antioxidants and help protect the body against free radicals, pathogens and the effects of UV radiation, according to May 2017 research published in Nutrients. Simply put, polyphenols help protect us from all of the daily damage thrown in our paths. They also have good street cred for fighting some of the toughest health conditions out there.
Read more: OK, But What Are Antioxidants Really?
1. They're Tied to Fighting Cancer
One of the largest bodies of evidence in research on polyphenols is on their effect on cancer. According to September 2016 research published in Nutrients, polyphenols exhibit anti-cancer activity for breast cancer, prostate cancer, colorectal cancer, pancreatic cancer, lung cancer, colorectal fibrosarcoma and leukemia.
Some polyphenols may block cancer-causing compounds, while others may interfere with cancer progression, per Harvard Health Publishing. However, note that most of these studies are correlative, not causative, so there's no guarantee to the benefit.
2. Polyphenols Are Linked to Good Heart Health
If you're looking to improve your heart health, eating foods high in polyphenols might be your ticket. According to a May 2013 review, people who had the highest intake of flavonoids, a class of polyphenols, were observed to have 18 percent fewer deaths from heart disease, per research in Current Atherosclerosis Reports.
Flavonoids are found in foods such as berries, citrus, black beans, cocoa, onions and green tea.
Read more: 11 Simple Ways to Keep Your Heart Healthy and Strong
3. They're Potent Inflammation-Fighters
Inflammation is a natural process that everyone experiences occasionally. Ever had a fever? That's inflammation. The problem happens when that short term, or acute, inflammation turns into long-term, aka chronic inflammation.
In fact, chronic inflammation is involved in the development of type 2 diabetes, heart disease and obesity, according to a September 2016 study published in Oxidative Medicine and Cellular Longevity.
But multiple polyphenols, such as those in turmeric, red grapes and onions can disrupt pro-inflammatory pathways in the body, thus blocking the development of inflammation in the first place, a November 2018 review published in Nutrients found. Indeed, the flavonoids and quercetin in citrus, apples and onions can help reduce inflammation in the body, per Harvard Health Publishing.
4. Polyphenols Can Boost Your Gut Health
If there's one health buzzword you're sure to have heard about, it's the gut. And flavonoids, such as those found in berries, dark chocolate, coffee and tea may have prebiotic properties and may alter your gut composition to stimulate the growth of good bacteria, according to a September 2018 article published in Nutrients.
"I love eating dark purple and blue fruits to up my intake of anthocyanins," Andrea Hardy, RD of Ignite Nutrition, tells LIVESTRONG.com. "Some preliminary research show they have prebiotic-like effects in the gut, deeming them good for me and my gut microbiota."
A February 2015 review study published in the European Journal of Nutrition indicates that several foods rich in polyphenols, including tea, citrus, red wine, berries and cranberries, are associated with increasing the good bacteria in the gut.
5. They're Linked to Reducing Your Diabetes Risk
A diet rich in polyphenols usually means a diet full of fruits, vegetables, legumes and whole grains — typically the type of diet recommended to prevent and manage type 2 diabetes.
There may be more to it than just diet management: According to November 2018 research published in Critical Reviews in Food Science and Nutrition polyphenol-rich foods, such as cocoa, coffee, red wine, olive oil and chocolate may improve vascular function and reduce insulin resistance and levels of HbA1c, a measure of blood sugar.
Read more: A Heart-Healthy Diet Plan for People With Diabetes
Types of Polyphenols and Where to Find Them
Did you know there are more than 8,000 types of polyphenols? Picking the best polyphenol is like trying to pick a favorite child. There are some types that deliver more, but you can't go wrong with loading up your daily diet with all foods that contain polyphenols.
Check out this list of foods high in polyphenols to see if your favorites made the cut, but know this is not all-inclusive since there are over 8,000 types after all!
Flavonoids make up the largest and most-studied class of polyphenols. This class contains the famous quercetin, anthocyanin, hesperetin and genestein. Black tea and green tea take the prize for the most potent polyphenol source in this group, per a May 2015 study in Current Atherosclerosis Reports.
Heidi Moretti, RD of The Healthy RD, loves to get her flavonoids from a popular fruit: "Bananas are rich in antioxidants like l-dopamine and catechins. The riper they are, the more antioxidants they have."
Sources of flavonoids include:
- Fruits: berries, citrus, cherries, apples, grapes, peaches, olives, plums, bananas
- Vegetables: spinach, onions, shallots, garlic
- Beans: soybeans, black beans, tofu
- Nuts: hazelnuts, almonds
- Flavorings: cocoa, extra-virgin olive oil, capers, oregano
- Drinks: tea, red wine
Phenolic acids have been studied for their cardioprotective and anti-cancer effects, most notably from two compounds in this category, caffeic acid and ellagic acid, according to September 2015 research published in Advances in Pharmacological Sciences.
Sources of phenolic acids include:
- Extra-virgin olive oil
- Red wine
Stilbenes contain the much-researched compound resveratrol, which is abundant in dark grapes and red wine.
Grapes contain polyphenols that promote heart and eye health as well as healthy aging, Malena Lewis, RD, tells LIVESTRONG.com. Plus, they're an easy, portable snack to grab and go with. While red wine is a popular source of resveratrol, it's still important to keep moderation in mind.
More is not better in this case: Adults over 21 years of age should limit themselves to no more than 2 servings for men and 1 glass for women per day.
Sources of stilbenes include:
- Red wine
- White wine
Lignans may be the least-studied polyphenol, but some popular foods are high in this phytochemical. According to a December 2018 article published in Molecules, the main sources of lignans in the diet are oils from sesame, flax, rapeseed (canola oil) and soy as well as from legumes, grains and berries.
Additional foods that contain lignans include:
- Rye flour
- Extra-virgin olive oil
- White cabbage
How to Get More Polyphenols in Your Diet
If you're looking for a way to increase the amount of polyphenols you take in every day, look no further than the Mediterranean way of eating. The Mediterranean diet is rich in fruits, vegetables, legumes and whole grains as well as seafood.
Getting more polyphenols in your diet is as simple as including a few extra plant foods onto your plate every day. Kacie Barnes, RDN of Mama Knows Nutrition, knows it doesn't have to be time-consuming to get more of these antioxidants.
"We eat berries weekly in my house, not only for their antioxidants, fiber and high nutrient content, but also for their ease!" Barnes says. "No peeling or chopping means we are much more likely to grab a handful instead of a handful of crackers."
Try these tips to get more polyphenols in your diet:
- Swap out vegetable oil for extra-virgin olive oil.
- Choose rye bread over white bread.
- Grab nuts or berries as a snack instead of anything made with refined grains or added sugar like chips, crackers and cookies.
- Go for dark chocolate over milk chocolate — the darker the bar, the more antioxidants.
- Choose red over white wine.
- Drink unsweetened green or black tea in place of soft drinks or juices.
What About Polyphenol Supplements — Do Those Work?
More research is needed to determine how getting polyphenols from a little pill compares to eating all that delicious food. In general, it's wise to choose whole foods over supplements: There's minimal regulation in the supplement industry and a lack of research on dosage for polyphenols and other compounds.
It's also possible that polyphenols have a synergistic relationship with the foods they're in — meaning, you may need more than just the polyphenol itself for your body to reap the benefits. In a nutshell, stick with foods and leave the supplements on the shelf.
- Oxidative Medicine and Cellular Longevity: "Oxidative Stress and Inflammation: What Polyphenols Can Do for Us?"
- Nutrients: "The Immunomodulatory and Anti-Inflammatory Role of Polyphenols"
- Nutrients: "A Critical Review on Polyphenols and Health Benefits of Black Soybeans"
- UC Davis Integrative Medicine: "The Power of Polyphenols?"
- Nutrients: "The Anti-Cancer Effect of Polyphenols against Breast Cancer and Cancer Stem Cells: Molecular Mechanisms"
- Harvard Medical School: "Fill Up on Phytochemicals"
- Current Atherosclerosis Reports: "Polyphenols, Inflammation, and Cardiovascular Disease"
- Nutrients: "Associations between Flavonoid Intakes and Gut Microbiota in a Group of Adults with Cystic Fibrosis"
- European Journal of Nutrition: "Interaction of Dietary Compounds, Especially Polyphenols, With The Intestinal Microbiota: A Review"
- Critical Reviews in Food Science and Nutrition: "Dietary Polyphenols and Type 2 Diabetes: Human Study and Clinical Trial"
- Advances in Pharmacological Sciences: "Therapeutic Potential of Dietary Phenolic Acids"
- Molecules: Dietary Lignans: "Definition, Description and Research Trends in Databases Development"
- Frontiers in Nutrition: "The Role of Polyphenols in Human Health and Food Systems: A Mini-Review"
- University of Maryland Medical Center: Green Tea