Flavonoids, also referred to as bioflavonoids, are a type of antioxidant found in fruits, vegetables, and certain beverages. The average dietary intake of flavonoids ranges between 50 to 800 mg per day, which is quite high compared to other dietary antioxidants, such as vitamin C (~70 mg), vitamin E (7-10 mg), and carotenoids (2-3 mg).
Flavonoids are a hot topic because of their reported antiviral, anti-allergy, antiplatelet (blood clotting), anti-inflammatory, anti-tumor (cancer), and antioxidants health benefits. Many of the beneficial effects of fruits, vegetables, tea, and red wine are linked to flavonoids versus known nutrients and vitamins.
Antioxidants protect cells against damage caused by free radicals, which lead to oxidative stress and cell damage. Oxidative stress is linked with cancer, aging, atherosclerosis, ischemic injury, inflammation, and neurodegenerative diseases. For example, the oxidation of LDL cholesterol plays a critical role in the development of heart disease.
Decreased Blood Pressure
Some flavonoids prevent atherosclerosis and promote the relaxation of arterial muscles, which allows arteries to dilate (widen) and blood flow to be easier. Other flavonoids reduce LDL oxidation and prevent platelets from sticking together. One study evaluated the affect of a plant rich in flavonoids on 120 men and women diagnosed with high blood pressure and high cholesterol. The study found significantly decreased systolic and diastolic blood pressure over a 6 month period linked to the plant flavonoids. Study participants also had reduced total cholesterol, LDL cholesterol, triglycerides, and increased HDL cholesterol. More studies are needed, but a there is a definite link between flavonoids and reduced blood pressure.
There are over 4,000 identified flavonoids, such as quercetin, xanthohumol, isoxanthohumol, and genistein, and their function varies.
High Flavonoid Content (>50 mg/100 g of food)
Onion, kale, green beans, broccoli, endive, celery, cranberry, orange juice
Medium Flavonoid Content (1-5 mg/100 g of food)
Salad, tomato, bell pepper, strawberry, broad bean, apple, grape, red wine, tea, tomato juice
Low Flavonoid Content (<1 mg/100 g of food)
Cabbage, carrot, mushroom, pea, spinach, peach, white wine, coffee
Flavonoids found in citrus fruits affect capillary permeability and blood flow. The flavonoids also contribute to anti-allergy and anti-inflammatory benefits. Some of the flavonoids found in citrus fruit have been used to treat easy bruising, hemorrhoids, and varicose veins.
Flavonoids found in green tea are thought to reduce cancer and heart disease. White tea, the least processed tea, has the highest level of flavonoids. Health benefits linked to tea flavonoids include decreased LDL oxidation, decreased cholesterol, and decreased triglyceride levels.
Both red and white wine contain flavonoids, but red wine has higher levels since fermentation occurs in the presence of grape skins (the source of significant amounts of flavonoids). Many studies have linked moderate red wine intake with protection against heart disease.