Around the year 400 B.C., Hippocrates, regarded as one of the most influential figures in the history of medicine and healing, advised people to prevent and treat diseases by eating a nutrient-dense diet. Fast forward to modern times, the concept of "food as medicine" has gained significant scientific credibility and is one of the key tenets of functional medicine.‍

‍Let food be thy medicine and medicine be thy food. — Hippocrates

In this article, we're digging into the chemistry of nutrition and investigating polyphenols.

What Are Polyphenols and Why Should I Care About Them?

Polyphenols are naturally occurring compounds

Polyphenols are a type of phytochemical (phyto meaning plant) produced in a variety of plant foods including spices, fruits, vegetables, seeds, and legumes. Plants developed them as an evolutionary defense mechanism to protect against environmental threats, including insects, diseases, etc. (Source, Source)

There are four categories of polyphenols

There are over 500 known polyphenols classified into four main categories based on their chemical structure (Source):

1. phenolic acids (found in coffee, tea, cherries—they're effective at fighting cancer and heart disease)
2. stilbenes (found in red wine and grapes—the least common type of polyphenol)
3. lignans (primarily found in flax seeds, fruits, vegetables, and legumes—shown to improve immune system health and hormone balance)
4. flavonoids (the most heavily studied with over 6000 types—responsible for giving foods their vibrant colors)

Polyphenols have antioxidant and anti-inflammatory properties

Among other health benefits, polyphenols are powerful antioxidants that help fight against cellular aging. They act as a shield to prevent cellular oxidation and are widely known for their preventive effects against inflammatory, cardiovascular, and neurodegenerative diseases, as well as certain types of cancer. (Source)

How do antioxidants work again? 

Free radicals are oxygen-containing molecules that form when atoms or molecules gain or lose electrons, either as part of normal metabolic processes or from environmental sources. They possess an uneven number of electrons, which makes them unstable, and easily react with other molecules, leading to oxidative stress in the body. Antioxidants function by donating an electron to the free radical, thereby stabilizing it and neutralizing its effect. Antioxidants are unique because they can donate an electron without becoming reactive free radicals themselves. (Source)

What Does the Research Show About Polyphenols?

Polyphenols protect your heart health

Studies suggest that higher polyphenol intake from fruits and vegetables is associated with decreased risk for cardiovascular disease. They inhibit LDL oxidation, a key mechanism in atherosclerosis (the hardening of your arteries), and they appear to have antiplatelet and anti-inflammatory effects as well. (Source)

Polyphenols feed your gut

Research has shown that polyphenol-rich foods have a "prebiotic-like" effect and can help grow the amount of good bacteria in your gut and prevent pathogenic strains. Your microbiome also impacts how well your body absorbs the polyphenols consumed, although more research is needed to understand the bi-directional relationship here. (Source)

Polyphenols fight aging

In one 12-year study, researchers found that people whose diets were rich in polyphenols experienced a 30% lower mortality rate than those whose diets were lower in polyphenols. Another recent study found that resveratrol, a chemical found in red wine, reduces the frequency of DNA double-strand breaks, which supports genomic stability. (Source, Source)

So What Should I Do About Polyphenols?

Taste the (organic) rainbow

Eat a colorful diet and you'll be enjoying a wide variety of polyphenol-rich foods. The fruits with the highest levels of polyphenols include black chokeberries, black elderberries, strawberries, red raspberries, blueberries, plums, and black currants. Olives, artichokes, and red onions are some of the most polyphenol-rich vegetables, and cocoa and dark chocolate also top the list. If possible, aim to eat organic too—studies show that industrial agriculture lowers polyphenol levels in food compared to organic and sustainable farming. (Source)

• Fun fact: the outer layers of many fruits and vegetables contain the highest concentrations of polyphenols, so eat the peel whenever possible.

Flavor your food with herbs and spices

As a rule of thumb, seasonings are the richest source of polyphenols, followed by seeds, fruits, and vegetables. According to the European Journal of Clinical Nutrition, cloves, dried peppermint, and star anise are the seasonings with the highest concentrations of polyphenols—with cloves having a total of 15,188 mg per 100 gram of cloves. (Source)

Freeze-dry at peak ripeness

Polyphenol activity reduces as food ripens, so if you can't consume fruits or vegetables immediately, then freeze-dry them to preserve their nutrients. One study showed that freeze-drying strawberries (as opposed to chilling) preserved 80% of its antioxidants, including polyphenols. (Source)

Steam your broccoli

Although consumption of raw vegetables is widely advocated, there is emerging evidence that suggests specific cooking methods may increase the content of polyphenols and their antioxidant activity. One study found that steaming fresh broccoli increased its polyphenol content, while cooking fresh broccoli in water reduced its polyphenol content. These results suggest there might be an ideal preparation method for each type of vegetable to increase the bioavailability of its polyphenols. (Source)

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Drink tea

Many studies have demonstrated the benefits of tea on human health, crediting many of their health-promoting properties to polyphenols. Although many teas contain polyphenols, green tea has the highest concentration of phenolic compounds in comparison to oolong or black tea. Green tea compounds have been linked to a reduced risk of cancer and other chronic diseases, including type 2 diabetes and cardiovascular disease. (Source, Source, Source, Source)

Cook with olive oil

Researchers found that cooking vegetables with extra virgin olive oil can increase the bioavailability of their polyphenols, making them more accessible and easier to absorb after this type of preparation. Cooking at the lowest possible temperature will help preserve the olive oil’s own polyphenol content. (Source, Source)

Where Can I Go to Learn More About Polyphenols?

On how polyphenols can promote healthy, glowing skin

Polyphenols not only benefit our insides but also our outsides. They're gaining popularity as ingredients in cosmetic formulations due to their natural repairing and anti-inflammatory effects on the skin. (Source)

On every polyphenol imaginable

For an exhaustive list of polyphenols, check out Phenol-Explorer, the first comprehensive database on polyphenol content in foods. The platform contains information on more than 500 different dietary polyphenols, including the foods in which they’re found, the metabolites they produce, and the effects of different types of preparation. (Source)