When you eat plant-based foods, you absorb a number of chemicals that offer benefits to that plant. Flavonoids are a group of compounds that:
. Give plants color so they can attract insects for pollination
. Protect plants against some plant disease
. Help to regulate plant growth
. Help to combat oxidative stress
This enormous class of compounds includes isoflavones, flavones, flavonols, anthocyanins, and flavans. In total, there are more than 5,000 types of flavonoids, although most have not been extensively studied. However, the ones that have shown these compounds benefit not only plant health but human health as well. In fact, flavonoids may explain many of the health benefits we attribute to plant foods like fruits and vegetables.
The Role of Flavonoids in Human Health
So often you hear about antioxidants and their ability to protect cells against free radical damage. Cells are constantly in motion, engaging in such activities as producing energy, packaging proteins, maintaining homeostasis and such activities require oxygen. The downside to this constant flurry of activity is it creates free radicals that damage cell structures and the genetic material inside. Such free radical damage is linked with aging and health problems like cancer.
Flavonoids, as a group, function as antioxidants, compounds that prevent cellular damage due to free radicals – but that’s not all flavonoids do. They have the ability to turn on enzymes that protect cells in other ways. At the tissue level, some flavonoids strengthen tiny blood vessels called capillaries and make them less fragile. Research also suggests they block enzymes that break down collagen, the protein that gives your skin and joints strength and support.
Where Do You Find Flavonoids?
The good news about flavonoids is you find them in almost all plant-based foods. The problem is some cooking methods that expose plant foods to high heat for long periods of time, reduce their flavonoid content. In that respect, raw food lovers are right on target. On the other hand, cooking can enhance the release of some nutrients from food, so the best approach for overall health may be to eat both raw and cooked foods.
As you might expect, fruits and vegetables of all types are rich in flavonoids but so are nuts, seeds, and legumes. The class of flavonoid varies depending on the plant. For example, berries, particularly blueberries, are known to be high in flavonoids called anthocyanins, while buckwheat is rich in a flavonoid called rutin that helps strengthen the inner walls of capillaries.
Onions and apples are an excellent source of quercetin, a flavonoid that helps reinforce and stabilize capillaries. Some research even suggests rutin and quercetin help prevent varicose veins and bruising by strengthening the walls of blood vessels. Isoflavones are a type of flavonoid abundant in soy-based foods like tofu and fermented soy products like tempeh and miso. Silymarin, a type of flavonoid found in artichokes and milk thistle, seems to protect against certain types of liver disease, including fatty liver and liver cancer.
Other plant foods that are particularly high in flavonoids of various types include black tea, green tea, red wine, dark chocolate, parsley, coffee, tomatoes, and citrus fruits.
How Else Might a Flavonoid-Rich Diet Be Beneficial?
Flavonoids have anti-inflammatory activity and may lower the risk for a number of diseases, including heart disease, type 2 diabetes, and some forms of cancer. Dietary flavonoids may reduce the risk for heart disease in other ways: by blocking the oxidation of LDL-cholesterol and by improving blood vessel function and lowering blood pressure.
Interestingly, flavonoids may be beneficial for weight control. Research in mice shows flavonoids have the ability to increase thermogenesis. Catechins in green tea, which seem to stimulate thermogenesis, are a type of catechin. In some studies, grape juice shows the same metabolism-boosting benefits, possibly due to its high level of flavonoids. Some experts believe one reason nuts don’t cause the expected amount of weight gain because they contain flavonoids. Another reason to eat whole foods like fruits, vegetables, whole grains, and nuts!
Get Flavonoids Naturally from Plant-Based Foods
Although you can buy flavonoid supplements, taking flavonoids in isolation may not offer the same benefits as getting them naturally from plants. They could even be harmful at high doses. Plants contain other secondary compounds that may work synergistically with flavonoids to provide benefits. Isolated flavonoids may not behave the same as they would in their natural surroundings. Plus, plants contain other components like fiber you don’t get when you take a supplement.
The flavonoids in plant-based foods vary to some degree based on how they were raised, the soil they grew up in, and how they were cooked. For example, onions lose 75% of their flavonoids when you boil them in water for 15 minutes. When you prepare plant-based foods, cook them lightly using a method that limits the amount of water such as steaming or sautéing to preserve flavonoids and other nutrients. Save the liquid and add it to soups or stews so none of the flavonoids are lost. Storage can also reduce the number of active flavonoids in plant-based foods.
Unfortunately, most of us don’t get enough dietary flavonoids, primarily because we don’t eat enough fruits and veggies. The best way to enjoy the benefits these food-derived chemicals offer is to eat more fruits and veggies. Skip the soft drinks and substitute green tea. Bite into an apple or citrus fruit as a snack, and make raw and cooked vegetables part of your diet.
The Bottom Line
What you eat matters when it comes to your health. Plant foods have so many benefits, among them being the flavonoids they contain. Make sure you’re getting your share!
References:
The Scientific World Journal Volume 2013 (2013), Article ID 162750, 16 pages.
Life Extension Magazine. “How Bioflavonoids Create Youthful Skin Tone”
Michigan Health System. University of Michigan. “Flavonoids”
Adv Nutr January 2011 Adv Nutr vol. 2: 8-14, 2011.
Int J Obes Relat Metab Disord. 2000 Feb;24(2):252-8.
NutritionFacts.org. “Fat Burning via Flavonoids”
J Am Coll Nutr. 2009 Oct;28(5):574-82.
Curr Pharm Biotechnol. 2012 Jan;13(1):210-7.
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