What Is It?
Flavonoids is the umbrella term given to some 4,000 compounds that impart the colorful pigment to fruits, vegetables and herbs. Also found in legumes, grains and nuts, flavonoids can act as effective antivirals, anti-inflammatories, antihistamines and antioxidants. They’re useful for reducing cancer risk and serve to prevent or treat a wide variety of conditions.
While research generally supports the healing potential of flavonoids, only a few have been widely studied. Some standouts include genistein, found in soybeans and some other legumes; quercetin, found in apples and onions; PCOs (procyanidolic oligomers, also known as proanthocyanidins), found in abundance in pine bark and grape seed extract, as well as in red wine; citrus flavonoids, including rutin and hesperidin, found in oranges, grapefruits, tangerines and other citrus fruits; and polyphenols, particularly EGCG (epigallocatechin-gallate), found in green tea. Researchers feel the latter may be the most effective cancer-battling compound discovered to date.
As antioxidants, flavonoids (or “bioflavonoids” as supplement manufacturers often label them) help prevent the cell damage caused by unstable oxygen molecules known as free radicals. They provide many other health benefits as well.
Specifically, flavonoids may help to:
Lower cancer risk. A high intake of such flavonoids as polyphenols and quercetin is linked to lower rates of stomach, pancreatic, lung, and possibly breast cancer. Taking the flavonoid genistein, a phytoestrogen that acts as a weak form of the hormone estrogen, may help prevent breast cancer and other hormone-related cancers, including prostate cancer, because it binds with estrogen receptors in the body’s cells.
Reduce the risk of stroke and heart disease. Studies indicate that a diet high in flavonoids, particularly quercetin and PCOs, may help prevent blood clots and blocked arteries, significantly reducing the chance of death from stroke or heart disease. Moreover, one recent study showed that drinking one or more cups of tea a day may also cut the risk of heart attack.
Protect against age-related vision disorders, such as cataracts and macular degeneration. A contributing factor to the development of cataracts is the accumulation of the sugar sorbitol in the eye’s lens. Studies show that the flavonoid quercetin inhibits this buildup. Grape seed extract, another flavonoid, also helps combat cataracts and prevent macular degeneration because it improves blood circulation in the eye.
Relieve hay fever, sinusitis, and asthma symptoms. Quercetin’s proven anti-inflammatory properties help the body counter allergic reactions to pollen. Quercetin also seems to reduce inflammation in the lungs and other air passages, making breathing easier.
Alleviate inflammatory skin conditions, such as eczema and bug bites. Quercetin’s anti-inflammatory properties can help treat these skin irritations.
Reduce inflammation in the joints and muscles common to fibromyalgia, gout, and rheumatoid arthritis. Because of its anti-inflammatory properties quercetin is often used to treat these conditions.
Minimize menopausal hot flashes. Genistein, plentiful in soy products, can lessen the symptoms of hot flashes because it can mimic the effects of estrogen in the body.
Shrink hemorrhoids and reduce varicose veins. Citrus flavonoids and PCOs help repair hemorrhoids and varicose veins by strengthening blood vessels.
Battle viral infections. Because flavonoids boost immunity, they help the body fight off illnesses and may speed recovery time. Note: Flavonoids have also been found to be useful for a number of other disorders. For information on these additional ailments, see the individual flavonoids: quercetin, ginkgo biloba, grape seed extract, green tea, soy isoflavones, and vitamin C and flavonoids.
For overall health: For best results, choose a pure flavonoid supplement that features at least one and possibly a combination of pure flavonoids (such as quercetin, green tea extract, or genistein). Follow the label directions for the exact dosage. Be sure to check out the Dosage Recommendations Charts for the separate flavonoids: quercetin, ginkgo biloba, grape seed extract, green tea, soy isoflavones, and vitamin C and flavonoids.
Guidelines for Use
Take quercetin 20 minutes before a meal; other flavonoids may be taken at any time.
If you buy a citrus bioflavonoid complex product, look for one that contains some pure rutin, pure hesperidin or both. Mixed citrus bioflavonoid complexes without these may be inexpensive, but they are often less potent.
Take flavonoids along with vitamin C, if possible, to maximize both of their benefits (flavonoids help increase the absorption of vitamin C). Buying vitamin C and flavonoid supplements separately usually costs less than purchasing a “vitamin C/flavonoid complex” formulation that combines the two; doing so may also provide greater dosage flexibility.
Recent studies indicate that taking antioxidants such as flavonoids could decrease the effectiveness of many anti-cancer chemotherapy and radiation treatments if taken at the same time. Restart the antioxidants during the rest period between chemotherapy or radiation treatments.
Avoid taking a citrus flavonoid preparation containing naringin (a flavonoid present in grapefruit juice but not orange juice) when using an immunosuppressant drug, such as tacrolimus (Prograf).
Don’t take naringin if you are on a calcium channel blocker, such as amlodipine (Norvasc), nifedipine (Procardia) or verapamil (Calan), because it may amplify the effect of the drug and cause a serious drop in blood pressure.
Naringin may also inhibit the breakdown of various drugs, particularly caffeine, coumarin and estrogens. Note: For information on interactions with specific generic drugs, see our WholeHealth Chicago Drug/Nutrient Interactions Chart.
Possible Side Effects
No side effects are presently known.
Flavonoids should be used as complements to–not replacements for–the standard methods of treating cancer, heart disease and other serious illnesses.
David Edelberg, MD