Polyphenols, a group of plant compounds found in a wide range of fruits, vegetables, herbs, tea, red wine, coffee, and dark chocolate. These natural compounds have been studied extensively for their antioxidant properties, which help protect the body from damage caused by free radicals. Epidemiological studies and meta-analyses have suggested that diets rich in polyphenols may offer protection against various diseases, including cancers, cardiovascular diseases, diabetes, osteoporosis, and neurodegenerative diseases. [1]
While there are more than 8,000 identified polyphenolic compounds, researchers are still uncovering how these chemicals specifically affect the human body. In this article, we will explore the different types of polyphenols, their potential health benefits, and any associated risks.
Types of Polyphenols
Flavonoids, the most extensively studied group of polyphenols, make up over half of all known polyphenols. They are found in foods such as onions, kale, parsley, tea, red wine, and soybeans. Flavonoids can be further classified into five different types: anthocyanins, flavan-3-ols, flavones, flavanones, and flavonols. [2]
Phenolic acids, another group of polyphenols, are found in grapes, berries, pomegranates, walnuts, chocolate, coffee, and green tea. They account for about 30% of all known polyphenols and can be divided into two classes: hydroxybenzoic acid and hydroxycinnamic acid. [3]
Polyphenolic amides, including capsaicinoids found in chili peppers and avenanthramides found in oats, form a smaller subgroup of polyphenols. [4]
There are also other polyphenols that exist in smaller quantities but still have significant health benefits. Resveratrol, for example, is unique to grapes and red wine. Ellagic acid is found in berry fruits, such as strawberries and raspberries, as well as the skin of tree nuts. Curcumin, a potent antioxidant, gives turmeric its distinctive yellow color. Lignans are found in flaxseeds, sesame seeds, and some other grains. [5]
Health Benefits of Polyphenols
The primary health benefits of polyphenols stem from their antioxidant properties. Antioxidants help protect cells from damage caused by free radicals, which are highly reactive oxygen molecules produced by normal cell processes, radiation, air pollution, smoking, or chemical exposure. By neutralizing free radicals, polyphenols may help maintain healthy cells and potentially reduce the risk of certain diseases.
While more research is needed to fully understand all the benefits of polyphenols, there is evidence to suggest that they may offer the following health advantages:
Lower Blood Sugar Levels
Regular consumption of polyphenol-rich foods has been associated with a lower risk of developing type 2 diabetes. Studies have shown that polyphenols, such as those found in tea, coffee, and berries, can help regulate blood sugar levels by protecting insulin-producing cells, reducing inflammation, and preventing rapid digestion of starches and simple carbs. [6]
Increase Insulin Sensitivity and Polyphenols
Polyphenols from strawberries and cranberries have been shown to increase insulin sensitivity in individuals with insulin resistance, a potential precursor to type 2 diabetes. By improving insulin sensitivity, polyphenols help cells take up glucose from the bloodstream more effectively. [7]
Lower Cancer Risk
Polyphenols, particularly flavonoids, may reduce the risk of developing certain types of cancer, including colon, prostate, skin, endometrial, and breast cancer. These compounds help prevent cell damage and control tumor cell growth, potentially reducing the likelihood of cancerous cell formation. [8]
Polyphenols Reduce Inflammation
Chronic inflammation is associated with an increased risk of various health conditions, including heart disease, diabetes, cancer, and autoimmune diseases. Polyphenols, such as lignans, have been shown to lower markers of inflammation in the body, promoting overall health and reducing the risk of inflammatory diseases. Curcumin and resveratrol both being well studied examples of this, having a notable impact in several arthritis studies. [9]
Improve Heart Health
Polyphenols have been linked to improved heart health by lowering blood pressure, reducing LDL ("bad") cholesterol levels, increasing HDL ("good") cholesterol levels, and potentially preventing blood clots. Resveratrol, lignans, and flavonoids are among the polyphenols that have demonstrated heart-protective effects. [10]
Boost Brain Function
Certain polyphenols, like curcumin found in turmeric, may enhance brain function and protect against neurodegenerative diseases like Alzheimer's. Green tea consumption has also been associated with a lower risk of cognitive decline. The antioxidant effects of polyphenols and their ability to improve blood flow to the brain contribute to their potential benefits for brain health. [11]
Improve Digestion
Polyphenols may promote healthy digestion by supporting the growth of beneficial gut bacteria and inhibiting the growth of harmful bacteria. Blueberries and green tea, for instance, have been shown to stimulate the growth of beneficial bacteria while suppressing the growth of harmful ones like C. diff and E. coli. [12]
Polyphenol-Rich Foods
There are also certain polyphenols that have unique interactions with cells in the body turning off certain negative processes. However, it should be noted, many of these examples, such as the curcumin we mentioned only making up a small percentage of trumeric, and requiring 500-1000mg to be effective, which you'd need 10-15 grams of the spice if it weren't directly extracted. This means it's not really viable to get it from food alone.
To enjoy the health benefits of polyphenols, it is important to incorporate polyphenol-rich foods into your diet. Here are some examples of foods high in polyphenols:
Vegetables - Broccoli, carrots, spinach, red lettuce, onions, asparagus, artichokes, shallots, and garlic are all excellent sources of polyphenols.
Fruits - Blueberries, strawberries, raspberries, blackberries, cranberries, grapes, cherries, lemon, grapefruit, oranges, pears, apples, peaches, plums, pomegranate, nectarines, and apricots are rich in polyphenols.
Grains - Oats, rye, and wheat are grains that contain significant amounts of polyphenols.
Nuts and Seeds - Walnuts, almonds, flaxseeds, chia seeds, pecans, chestnuts, and hazelnuts are excellent sources of polyphenols.
Legumes - Black beans, white beans, soybeans, tofu, and tempeh are legumes that provide polyphenols.
Herbs and Spices - Turmeric, cinnamon, cumin, cloves, celery seed, basil, ginger, marjoram, parsley, peppermint, oregano, rosemary, sage, thyme, and lemon verbena are all rich in polyphenols.
Other - Green tea, black tea, red wine, dark chocolate, cocoa powder, coffee, and vinegar are additional sources of polyphenols.
Risks and Side Effects of Polyphenol Supplements
Including polyphenol-rich foods in your diet is generally safe for most people. However, caution should be exercised when considering polyphenol supplements. Supplements are not regulated by the FDA and often provide higher doses of polyphenols than what can be obtained from food sources.
There isn't a universal answer for all polyphenols as they aren't the same. More research is needed to determine the safety and effectiveness of many polyphenol supplements. It is always advisable to consult with a healthcare professional before incorporating any new supplements into your routine.
It is worth noting that certain polyphenol-rich foods, like those high in fiber, can cause digestive discomfort, such as gas, bloating, and constipation, especially when consumed in large quantities. Gradually increasing the intake of these foods can help minimize these side effects.
Lectins, which are present in some plant-based foods like raw legumes and whole grains, may disrupt digestion and potentially cause nutrient deficiencies. Soaking and cooking foods with lectins can help reduce their content and minimize any adverse effects.
Are Polyphenols Good for You?
Polyphenols are natural compounds found in a wide variety of plant-based foods. With their antioxidant properties, polyphenols offer numerous potential health benefits, including lower blood sugar levels, increased insulin sensitivity, reduced cancer risk, decreased inflammation, improved heart health, enhanced brain function, and better digestion. By incorporating polyphenol-rich foods into your diet, you can harness the power of these compounds to support your overall health.
References
1 - https://pubmed.ncbi.nlm.nih.gov/35694805/
2 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5465813/
3 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6734135/
4 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3257627/
5 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6429205/
6 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4728631/
7 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6014790/
8 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8565650/
9 - https://pubmed.ncbi.nlm.nih.gov/35694805/
10 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3820045/
11 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3372091/
12 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6160559/
