Polyphenols are plant compounds that give many fruits and vegetables their bright colors.
These plant compounds are some of the best antioxidants in the diet, and they have anti-inflammatory properties that are good for your brain, heart and gut health.
There are over 8,000 different types of polyphenols, and they’re found in a wide range of foods, including green tea, red wine, cocoa, nuts, herbs and spices.
Here are 11 reasons why polyphenols are good for your health.
1. Strong Antioxidants
Polyphenols are the most common antioxidants in the diet.
They’re also very important for your overall health. In fact, people who eat a lot of antioxidants have lower rates of death and cancer (6).
One study in 86 overweight or obese people found that following a diet rich in polyphenols for eight weeks significantly reduced oxidative stress (7).
These studies suggest that by reducing oxidative stress, polyphenol-rich foods may reduce the risk of many other diseases like obesity, diabetes and cancer.
Summary: Polyphenols are strong antioxidants that can help prevent cell damage caused by oxidative stress.
2. May Help Lower Cholesterol
High blood cholesterol is a major risk factor for heart disease, the leading cause of death in the world (10).
One study found that a polyphenol-rich diet significantly reduced triglycerides and “bad” very low-density lipoprotein (VLDL) cholesterol in overweight and obese people (15).
What’s more, one large study of over 1,200 people showed that eating polyphenol-rich berries could also lower “bad” LDL cholesterol (22).
Summary: Strong evidence shows that polyphenol-rich diets and foods, such as berries and olive oil, can lower “bad” cholesterol and increase “good” cholesterol.
3. May Help Lower Blood Pressure
High blood pressure is another risk factor for heart disease (23).
Polyphenols may help the endothelium — the inside layer of the blood vessels — relax, thereby reducing blood pressure (24).
Olives and olive leaves also contain many polyphenols, and it’s one reason why olive oil is one of the healthiest oils.
Moreover, a couple of studies have shown that drinking polyphenol-rich grape, bilberry or strawberry juice for 6–12 weeks can reduce blood pressure in both healthy people and those with high blood pressure (28, 29).
Another study found that polyphenols from oranges or orange juice could improve the health of blood vessels (30).
Summary: Polyphenols may help relax the blood vessels. Therefore, polyphenol-rich foods like olive oil, green tea and certain fruit juices may help lower blood pressure.
4. May Help Prevent Certain Cancers
Polyphenols may also help prevent certain cancers by reducing oxidative stress, inflammation and cancer cell growth (31).
However, there’s very little evidence of this effect in human studies. Rather, most of the evidence is from observational or test-tube studies (31).
The evidence on digestive tract cancers is mixed. Some studies have shown that a higher flavonoid intake reduces the risk of esophageal and gastric cancer, while others have shown no effect (32, 33, 34, 35).
The effects of polyphenols on other types of cancer appear to be stronger. In fact, women with higher intakes of various polyphenols may have lower rates of breast, ovarian and endometrial cancers (36, 37, 38).
For example, one study showed that eating a polyphenol-rich supplement from pomegranate, green tea, broccoli and turmeric for six months significantly reduced PSA in men with prostate cancer (43).
This is an interesting area of research, and more studies may show the importance of polyphenols in preventing or fighting cancer.
Summary: Polyphenols may help reduce certain cancers, especially prostate cancer, through their anti-inflammatory and antioxidant effects. However, not enough studies have been conducted in humans to confirm this.
5. Good for Gut Health
When you eat polyphenols, only 5–10% of them are absorbed into your body in your small intestine (44).
The remaining 90–95% travel down into your colon, where trillions of bacteria break them down into smaller molecules (44).
As a result, many polyphenols act as a food source for the healthy bacteria in your intestines.
Grapes are a good source of polyphenols, and there are many polyphenols in wine.
A number of studies have shown that red wine extracts help the growth of some beneficial bacteria in the intestines, such as Akkermansia. Akkermansia is a healthy bacteria that may aid weight loss (45, 46).
Other polyphenols have also been shown to increase levels of Bifidobacteria, which are healthy bacteria often used as probiotics, and short-chain fatty acids, which are important for gut health (47, 48)
Summary: The majority of polyphenols aren’t absorbed in the small intestine and instead travel to the large intestine, where they may promote the growth of healthy gut bacteria.
6. May Lower Blood Sugar and Diabetes Risk
High blood sugar can increase the risk of diabetes. Fortunately, polyphenols may reduce the risk of diabetes by helping insulin keep blood sugar under control.
A large study including over 250,000 people found that those with the highest intake of flavonoid polyphenols had a 9% lower risk of diabetes, compared to those with the lowest intakes (49).
A similar study found that people who ate a lot of polyphenol-rich foods, such as blueberries, apples and pears, also had a lower risk of type 2 diabetes (50).
Summary: There is strong evidence to suggest that different polyphenols can reduce blood sugar and other risk factors for diabetes.
7. Support Bone Health
Oxidative stress and inflammation can also damage your bones (57).
Bone damage can eventually lead to diseases like osteoporosis, which increases the risk of bone fractures.
One group of polyphenols called isoflavones, which are found in soy products, have been shown to benefit bone health.
A large two-year study found that women who took 120 mg of soy isoflavones every day experienced much less bone loss than those who didn’t take them (62).
Nevertheless, a large study that combined the results of 10 other studies found that taking at least 90 mg of soy isoflavone polyphenols daily for six months significantly increased bone density in menopausal women (67).
Summary: Polyphenols, particularly soy isoflavones, may support bone health. This is especially true later in life when they can reduce the risk of bone diseases like osteoporosis.
8. May Reduce Inflammation
Inflammation occurs when the immune system is activated to fight an infection.
However, if inflammation persists for long periods, it can contribute to many disorders, such as obesity, diabetes and heart disease (71).
Polyphenols may help reduce inflammation, and cocoa polyphenols may be particularly effective at reducing inflammation.
A number of studies have shown that if cocoa polyphenols are eaten for anywhere from five days to six weeks, they can reduce inflammation in those at high risk of heart disease and insulin resistance (72, 73, 74).
Yet, combining polyphenols may be even more effective. A recent study found that eating a mix of polyphenols for 15 days reduced inflammation in women (77).
Summary: Polyphenols, especially those from cocoa, have anti-inflammatory properties. They may benefit a variety of conditions.
9. May Help Prevent Weight Gain
Polyphenols may help prevent weight gain in people who are obese, overweight or normal weight.
A recent study found that a higher intake of polyphenols was associated with significantly reduced weight in over 100,000 people (78).
Green tea is high in polyphenols and is the most commonly consumed drink in Asian countries, after water.
Importantly, green tea can help you prevent weight gain and even lose weight naturally. It may do this by reducing food intake and the formation of fat cells, as well as by increasing energy expenditure, all of which help prevent weight gain (79).
A large study that combined the results of 10 other studies found that taking green tea polyphenols for at least 12 weeks led to more than a 2.2-pound (1-kg) weight loss. More importantly, these people didn’t regain the weight (80).
Summary: Some polyphenols, especially those found in green tea, may help you lose weight and keep it off.
10. May Help Slow Brain Degeneration
As you age, your brain health can begin to decline, possibly leading to diseases like Alzheimer’s.
Polyphenols may help prevent brain health degeneration by helping reduce oxidative stress and inflammation, two factors that may play a role in it (81).
A few studies have examined the polyphenol intake of people over the age of 65 and assessed their brain health 5 and 10 years later.
Grapes contain a number of important polyphenols. One study showed that older people with mild cognitive decline showed significantly improved verbal learning after drinking grape juice for 12 weeks (84).
A study in healthy older people examined the effects of drinking blueberry juice and found similar results (85).
Another study found following a diet with either a lot of polyphenol-rich fruits and vegetables or drinking a polyphenol-rich cocoa beverage could increase a chemical called brain-derived neurotrophic factor (BDNF) in both young and older people (86).
BDNF is an important chemical involved in learning. This study also found that the polyphenol-rich diets improved cognition.
Summary: Some evidence suggests that polyphenols can improve brain health in the elderly by reducing inflammation and oxidative stress. Yet, more studies are needed.
11. Found in Many Common, Delicious Foods
One great thing about polyphenols is that they are found in many delicious foods.
Given that there are many types of polyphenols, it’s important to eat a wide variety of foods that contain them, especially fruits and vegetables.
One study identified the 100 richest dietary sources of polyphenols. Below are some of these foods and their polyphenol content (91).
- Cocoa powder: 3,448 mg per 100 grams
- Dark chocolate: 1,664 mg per 100 grams
- Flaxseeds: 1,528 mg per 100 grams
- Dried rosemary: 1,018 mg per 100 grams
- Blueberries: 836 mg per 100 grams
- Black olives: 569 mg per 100 grams
- Hazelnuts: 495 mg per 100 grams
- Strawberries: 235 mg per 100 grams
- Coffee: 214 mg per 100 grams
- Almonds: 187 mg per 100 grams
- Red wine: 101 mg per 100 ml
- Green tea: 89 mg per 100 grams
This list is just a sample, and there are many other sources of polyphenols, making it easy to get a wide variety of them through your diet.
Summary: Polyphenols are found in many delicious foods, such as red wine, dark chocolate and berries, so it’s easy to get a lot of them through your diet.
The Bottom Line
Polyphenols are plant compounds that are extremely important for your health.
Their main health-promoting property is their antioxidant effect, but they also have a number of beneficial health effects, including reducing inflammation.
Many studies have shown that polyphenols can reduce the risk and improve the symptoms of many diseases, including diabetes, heart disease and bone health.
Fortunately, these healthy compounds are found in many delicious foods, including dark chocolate, coffee, berries and red wine.
By eating a wide range of these foods in moderation, you can reap the many health benefits of polyphenols.