Citrus Bioflavonoids Overview
Citrus fruits are well known for providing ample amounts of vitamin C . But they also supply bioflavonoids, substances that are not required for life but that may improve health. The major bioflavonoids found in citrus fruits are diosmin, hesperidin, rutin, naringin, tangeretin, diosmetin, narirutin, neohesperidin, nobiletin, and quercetin.
This article addresses the first five bioflavonoids listed above. Please see the article Quercetin for information on this supplement. A modified form of rutin, oxerutin , is also discussed in its own article.
Citrus bioflavonoids and related substances are widely used in Europe to treat diseases of the blood vessels and lymph system, including hemorrhoids , chronic venous insufficiency , leg ulcers, easy bruising , nosebleeds , and lymphedema following breast cancer surgery . These compounds are thought to work by strengthening the walls of blood vessels. Bioflavonoids are also often said to act as antioxidants; however, while they do have antioxidant activity in the test tube, growing evidence suggests that they do not act as antioxidants in people. ^
Citrus fruits contain citrus bioflavonoids in varying proportions. Even different brands of citrus juice may vary widely in their bioflavonoid concentrations and composition. ^ For use as a supplement, bioflavonoids are extracted either from citrus fruits or other plant sources, such as buckwheat.
A typical dosage of citrus bioflavonoids is 500 mg twice daily. The most studied citrus bioflavonoid treatment is a special micronized (finely ground) combination of diosmin (90%) and hesperidin (10%).
What Is the Scientific Evidence for Citrus Bioflavonoids?
A 2-month, double-blind, placebo-controlled trial of 120 individuals with recurrent hemorrhoid flare-ups found that treatment with combined diosmin and hesperidin significantly reduced the frequency and severity of hemorrhoid attacks. ^ Another double-blind, placebo-controlled trial of 100 individuals had positive results with the same bioflavonoids in relieving symptoms once a flare-up of hemorrhoid pain had begun. ^ A 90-day, double-blind trial of 100 individuals with bleeding hemorrhoids also found significant benefits for both treatment of acute attacks and prevention of new ones. ^ Finally, this bioflavonoid combination was found to compare favorably with surgical treatment of hemorrhoids. ^ However, less impressive results were seen in a double-blind, placebo-controlled study in which all participants were given a fiber laxative with either combined diosmin and hesperidin or placebo. ^ Two studies claimed to find that diosmin/hesperidin reduces pain after hemorrhoid surgery. ^ In fact, these studies show little to nothing, as the researchers failed to use a placebo group, and simply compared treated participants to untreated participants. (For information on why this matters, see Why Does this Database Rely on Double-Blind Studies? )
Overall, the evidence remains incomplete, though promising. ^
#Chronic Venous Insufficiency
A 2-month, double-blind, placebo-controlled trial of 200 people with relatively severe chronic venous insufficiency found that treatment with diosmin/hesperidin significantly improved symptoms as compared to placebo. ^ Another double-blind, placebo-controlled trial of diosmin/hesperidin enrolled 101 people with relatively mild chronic venous insufficiency. ^ The results showed little difference between the two groups; the authors theorize that diosmin/hesperidin might be more effective in severe chronic venous insufficiency.
A 2-month, double-blind, placebo-controlled trial evaluated the effects of diosmin/hesperidin in 107 people with nonhealing leg ulcers (sores) caused by venous insufficiency or other conditions. ^ The results indicated that treatment significantly improved the rate of healing.
Also, a 3-month, double-blind, placebo-controlled trial of 67 individuals evaluated buckwheat tea (a good source of rutin) for chronic venous insufficiency. ^ The results showed less leg swelling in the treated group.
One study supposedly showed that the supplement oxyrutin is more effective than diosmin/hesperidin for chronic venous insufficiency, but the study was too poorly designed to provide meaningful results. ^
Some people bruise particularly easily due to fragile capillaries. A 6-week, double-blind, placebo-controlled study of 96 people with this condition found that combined diosmin and hesperidin decreased symptoms of capillary fragility, such as bruising and nosebleeds. ^ Two rather poorly designed studies from the 1960s found benefits with a combination of vitamin C and citrus bioflavonoids for decreasing bruising in collegiate athletes. ^
Breast cancer surgery sometimes causes persistent swelling of the arm (lymphedema) caused by damage to lymph vessels. Citrus bioflavonoids as well as other natural supplements have shown promise for this condition. In a 3-month, double-blind study, 57 women with lymphedema received either placebo or combination therapy consisting of the modified citrus bioflavonoid trimethylhesperidin chalcone plus the bioflavonoid-rich herb butcher’s broom . ^ The results indicated that use of the bioflavonoid combination resulted in significantly less swelling.
In a review of 12 studies involving over 5,000 cases, researchers found that people who consumed the highest amounts of flavonoids in their diets had a lower risk of lung cancer than those who consumed less. ^ The significance of these results is weakened by the fact that none of the studies were controlled trials, and the most favorable among them did not account for the quantity of fruits, vegetables, or vitamins in the participants' diets.