You've heard that eating the rainbow is good for your health. But do you know why? Plant foods contain special compounds called flavonoids, which are plant-based nutrients that offer countless health benefits from reducing inflammation and slashing your risk of certain diseases.
Flavonoids act as antioxidants, which may play a significant role in heart health and may help to prevent diseases such as cancer caused by free-radical damage. Eating foods rich in flavonoids reduced the risk of cardiovascular disease and cancer, and the impact of this was even stronger in those who smoked or drank a lot of alcohol — two groups with historically high levels of inflammation, according to an August 2019 study published in Nature. What's more, flavonoids may also provide benefit in the prevention of other chronic conditions such as osteoporosis and diabetes.
Now that you know what flavonoids are, note that they fall under six subgroups: flavonols, flavones, isoflavones, flavanones, chalcones and anthocyanins, according to a December 2016 study in the Journal of Nutritional Science.
While it's easy to get confused with all of the fancy antioxidant names, think of it this way — the overarching group that encompasses flavonoids is called polyphenols. Flavonoids are then divided into the subgroups, and pretty much all the good-for-you plant-originating foods fall into these categories.
Read more: Top 10 Healthiest Fruits and Vegetables
Flavonols are the largest and most well-known subgroup of flavonoids. Flavonols, especially quercetin, have been studied extensively for their role as an antioxidant. Oxidative damage to the body is responsible for neurodegenerative diseases like Alzheimer's and Parkinson's and many cancers. Flavonols help protect the body against this type of damage, according to an extensive July 2016 review study published in Pharmacognosy Review.
Foods rich in flavonols include:
- Red wine
- Green tea
One of the major health benefits from flavones is their anti-inflammatory effect, according to a June 2016 study in Plants. Inflammation is usually the common thread between many chronic conditions, such as obesity, diabetes, and cancer as well as in people who smoke.
"Some research suggests that certain flavonoids (flavones and flavonols) are beneficial for reducing the risk of breast cancer," Cathy Leman, RD and founder of Dam. Mad. About Breast Cancer, tells LIVESTRONG.com.
Foods rich in flavones include:
- Green pepper
- Olive oil
- Navel oranges
- Chamomile tea
The king of all plant proteins is the soybean, which is high in catechins and a particular type of flavonoid, isoflavones. Isoflavones have a mixed reputation because of their similarity in structure to estrogens. In fact, isoflavones have been found to block estrogens that can cause breast cancer, cervical cancer and prostate cancer, according to June 2016 research published in Nutrients.
Countries with a high intake of isoflavone-rich foods typically have lower rates of these types of cancer. Isoflavones are found in legumes and other common soy foods, such as miso and tofu.
Foods rich in isoflavones include:
- Soybeans (and soy products such as tofu)
- Alfalfa sprouts
Flavanones are found in citrus fruits, in the juice and in the peel — and yes, you can eat the peel. The flavanones are responsible for that bitter taste, which most people stay away from. Flavanones are antioxidants and anti-inflammatory, and they have been shown to lower cholesterol.
Hesperidin, the most common flavanone found in lemons, oranges and grapefruit, is currently being studied for its possible role in helping protect against neurodegenerative diseases, such as Alzheimer's, Huntington's, Parkinson's Disease and multiple sclerosis, according to February 2019 research published in Molecules.
Foods rich in flavanones include:
The word chalcone comes from the Greek word "chalco," which means copper, and is an indicator of the color of some of the natural sources of this flavonoid. As with many of the other subclasses of flavonoids, chalcones are studied because of their potential to stop the development of cancer, according to a 2015 study in Current Medicinal Chemistry.
Foods rich in chalcones include:
- Wheat products
Anthocyanins are the actual pigments in red-orange to blue-violet plant foods and are linked to heart health, brain health, vision improvement, antidiabetic and antiobesity properties, anti-inflammatory effects and chemoprevention and cancer protection, according to September 2015 research published in Advances in Nutrition and an August 2017 review study published in Food and Nutrition Research.
Foods rich in anthocyanins include:
- Red wine
- Sweet potatoes
How to Get More Flavonoids in Your Diet
Ready to reap flavonoids' multitude of health benefits? "If you want to increase flavonoids in your diet, eat an abundance and variety of vegetables and fruits and aim for at least 3 daily cups of vegetables and 2 cups of fruit a day, varying the colors to vary the micronutrients," Hayden James, RD and founder of Satiate Nutrition, tells LIVESTRONG.com.
"Put more plants on your plate! Build meals and snacks around fruits, vegetables, whole [unprocessed] soy, legumes and whole grains," says Leman.
Get creative with it: Zest citrus peels into your favorite foods or blend an array of fruits into your morning smoothie to get more flavonoids in your diet.
There are some fruits and vegetables that can interact with medications, so if you regularly take medication, speak with your doctor to find out which foods you should avoid. For example, grapefruit, which is high in flavonoids, should be avoided if you take certain statins. In addition, foods high in vitamin K, such as flavonoid-rich leafy greens, may interact with blood-thinning medication warfarin.
Read more: High Antioxidant Fruits & Vegetables
- Journal of Nutritional Science: "Flavonoids: An Overview"
- Nutrients: "Isoflavones: Anti-Inflammatory Benefit and Possible Caveats"
- Plants: "Flavones: From Biosynthesis to Health Benefits"
- Pharmacognosy Review: "Overviews of Biological Importance of Quercetin: A Bioactive Flavonoid"
- Nature: "Flavonoid Intake is Associated With Lower Mortality in the Danish Diet Cancer and Health Cohort"
- Molecules: "Hesperidin as a Neuroprotective Agent: A Review of Animal and Clinical Evidence"
- Advances in Nutrition: "Anthocyanins"
- Food and Nutrition Research: "Anthocyanidins and Anthocyanins: Colored Pigments as Food, Pharmaceutical Ingredients, and the Potential Health Benefits"
- Current Medicinal Chemistry: "Chalcones as Promising Lead Compounds on Cancer Therapy"
- NIH, PubMed: Flavonoids in Food and their Health Benefits