Flavonoids, or phytonutrients, are in lots of fruits and veggies. Here's why you need them

Though flavonoids aren't considered essential nutrients − meaning one's body doesn't require them to grow and develop − few food compounds do as good of a job staving off infection and chronic disease.

Considered an indispensable "component in a variety of nutraceutical, pharmaceutical, medicinal and cosmetic applications," per the Journal of Nutritional Science, flavonoids contain the health boost everyone needs and many are seeking − especially now in light of the Department of Health and Human Services' recent end of the COVID-19 public health emergency.

"They are nutritional superheroes," says Josh Redd, NMD, the founder of RedRiver Health and Wellness and author of "The Truth About Low Thyroid." Redd praises the compounds for being "well known for their antioxidant, anti-inflammatory and immune-boosting properties."

What are flavonoids?

Flavonoids are natural compounds, also known as phytonutrients, that are commonly consumed in one's everyday diet.

Though thousands of flavonoids have been successfully isolated, most fall into six major subtypes, "and each interact with our gut microbes to be broken down in different ways," explains Uma Naidoo, MD, director of nutritional and lifestyle psychiatry at Massachusetts General Hospital and the author of “This is Your Brain on Food."

The six flavonoids' subtypes include flavanols, flavanones, isoflavones, flavones, flavan-3-ols, and anthocyanins.

What foods are highest in flavonoids?

One distinction flavonoids have over some other nutrients is that they are present in a large number of foods. The compounds can be found in everything from popular fruits and vegetables to herbs, spices and even flowers. "Although you can get these compounds through supplements, it's best to eat a diet rich in colorful vegetables and low-glycemic fruits to get flavonoids," advises Redd.

And different subtypes of flavonoids are found in different foods, with each group containing their own nutritional benefits. Foods rich in subtype flavanols, for instance, help manage symptoms of cardiovascular disease and can be found in lettuce, tomatoes, onions, broccoli and peaches. And foods like beans, legumes and soy products are rich sources of subtype isoflavones − flavonoids that help keep one's hormones balanced.

Many other plant-derived products "such as extra dark natural chocolate, wine and teas," are also abundant in flavonoids, says Naidoo. So are lemons, red peppers, grains, parsley, grapefruit, celery, peppermint, apples, kale and scallions. "Almost all fruits, vegetables and herbs contain a certain number of flavonoids," explains Beth Czerwony, RD, a registered dietitian at Cleveland Clinic’s Center for Human Nutrition. "Typically, the darker the color, the higher level of flavonoids the food will contain," she says.

What do flavonoids do to the body?

Research shows that, in addition to the aforementioned benefits, flavonoids possess many other medicinal advantages. "Flavonoids are very rich antioxidants, which fend off radical oxygen species in the body and brain. By doing so they help protect us from diseases like heart disease, cancer and more," explains Naidoo. "Flavonoids also help to lower inflammation," she adds, making the nutrient especially beneficial as many diseases such as "anxiety, depression and more are now linked to inflammation," she says.

Redd says flavonoids also help lower blood pressure, reduce cholesterol levels, stabilize blood sugar levels, and improve brain function. "They work by neutralizing the harmful free radicals linked to the most common diseases today," he explains.

Naidoo suggests it's best to obtain flavonoids from natural sources, and not supplements, as there still needs to be "further study about the doses that are safe since there have been reports of toxic flavonoids," she says. And Czerwony says flavonoids occasionally have mild side effects to be aware of as well. "Some flavonoids have been shown to negatively interact with some foods," she says, "this can result in decreased absorption in the gastrointestinal (GI) tract."

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This article originally appeared on USA TODAY: What are flavonoids? What to know about the powerful antioxidants