Quercetin Doesnt Boost Immunity

BOONE, N.C.Quercetin, a flavonoid found in fruits and vegetables, supplementation at 500 and 1,000 mg/d for 12 weeks significantly increased plasma quercetin levels, but had no influence on measures of innate immune function or inflammation in community-dwelling adult females, according to a recent study (Br J Clin Nutr. May 26, 2010).The double blind, placebo-controlled trial randomized 120 female subjects (aged 3079 years) to one of three groups: 500 mg/d of quercetin (n=38), 1,000 mg/ d of quercetin (n=40) or placebo (n=42). Subjects ingested two soft-chew supplements twice daily during the 12-week study period.

Eighteen subjects had overlapping data. Quercetin supplementation at two doses compared with placebo increased plasma quercetin, but had no significant influence on blood leucocyte subsets, plasma IL-6 or TNF-alpha concentration, natural killer cell activity (NKCA), granulocyte oxidative burst activity or phagocytosis. NKCA was inversely correlated with BMI and body fat percentage, and positively correlated with self-reported physical fitness level.