Asthma And The Role Of Flavonoids

Flavonoids (or bioflavonoids) are water-soluble pigments found in plants that are important antioxidants and aid in the absorption of vitamin C. Originally called vitamin P, these substances include citrin, epicatechin, flavones, flavonols, hesperidin, quercetin, and rutin. While there is some debate over how to classify flavonoids, most authorities agree that they possess a variety of antihistamine, anti-inflammatory, antioxidant, and anti-viral activities. Because of these characteristics, flavonoids are used to treat blood vessel disorders, diabetes, night blindness, and minor injuries. Popular flavonoids include quercetin, found in onions, and genistein, commonly found in soy. Flavonoids are also found in wine, tea, apples, and citrus fruits. Apparently, an apple a day does keep the doctor away, according to a study from King's College, London, on the dietary habits of 9,709 individuals. The results, published in the American Journal of Respiratory and Critical Care Medicine in 2001, showed that people who ate two or more apples a week reduced their asthma risk by 28 percent.

 

Quercetin is structurally similar to the allergy drug disodium cromo-glycate and boasts a variety of anti-inflammatory and antioxidant effects, which is why it is useful for treating asthma. Perhaps even more important, there is evidence that quercetin inhibits leukotrienes and blocks histamine release. As you may recall, leukotrienes are a major contributor to the asthma cascade and some of the most effective asthma drugs work by inhibiting leukotrienes. There are presently no human studies on quercetin and asthma, but animal studies support the antiasthmatic action of this flavonoid.

 

 

As with the carotenoids, the best offense is a good defense—so, do as your mother said and eat your fruits and vegetables. Several flavonoid supplements are also available, and most authorities recommend 1,000 mg of citrus flavonoids daily. As for drug interactions, flavonoids can react with acyclovir, so check with your doctor before supplementing if you're taking this medicine.

 

 

Found in apples, beans, green and black tea, onions, and many leafy green vegetables, quercetin is used in the treatment of capillary disorders, arteriosclerosis, asthma, and diabetes. For asthmatics, the standard dose of quercetin is 400 mg two to three times a day. Side effects have not been reported; however, since quercetin can cause chromosomal abnormalities in bacteria, women who plan to become or are pregnant should not take quercetin. If you decide to supplement your diet, use quercetin chalcone, a water-soluble form that is more easily absorbed. Since quercetin can react with estradiol and felodipine, check with your doctor before supplementing if you are taking these medicines.