Bioflavonoids such as Quercetin, Rutin, and Hesperidin are vital through their ability to increase the strength of the capillaries (blood vessels) and to regulate their permeability. They assist Vitamin C in keeping collagen, the intercellular “cement” in healthy condition; are essential for the proper absorption and use of vitamin C; prevent Vitamin C from being destroyed in the body by oxidation; are beneficial in hypertension; help hemorrhages and ruptures in the capillaries and connective tissues and build a protective barrier against infections.
Quercetin, a bioflavonoid obtained from buckwheat and citrus fruits, appears to stabilize the membranes of the mast cells that release histamine. Since quercetin’s action is preventive, it’s best taken daily a week or two before pollen season and continued throughout. Quercetin is used widely for sinus problems and aids in capillary fragility. Yellow onions contain high levels of quercetin, an especially potent antioxidant with some anti-inflammatory properties. It should be avoided during pregnancy.
No toxicity has been identified with quercetin. If taken in large doses, however, it can cause the blood pressure to decrease. Quercetin is available in powder and capsule form. The recommended dose is 200-400mg tid, best taken before meals.