A 12-week supplementation with quercetin does not affect natural killer cell activity, granulocyte oxidative burst activity or granulocyte phagocytosis in female human subjects

• Published in: British journal of nutrition Vol. 104; no. 6; pp. 849 - 857
• Main Authors: Heinz, Serena A., Henson, Dru A., Nieman, David C., Austin, Melanie D., Jin, Fuxia
• Format: Journal Article
• Language: English
• Published: Cambridge, UK Cambridge University Press 28.09.2010
• Subjects: Adult; Aged; aglycone; anti-inflammatory agents; antioxidant activity; Antioxidants; Antioxidants - pharmacology; Biological and medical sciences; Blood; Body Composition; Body Composition - immunology; Body Mass Index; Cellular biology; Dietary Supplements; Double-Blind Method; drug effects; Feeding. Feeding behavior; Female; Finland; flavonols; fruits (food); Fundamental and applied biological sciences. Psychology; Granulocytes; Granulocytes - drug effects; Granulocytes - metabolism; human nutrition; Humans; Immune function; Immune response; Immune system; immunity; immunology; immunostimulants; Killer Cells, Natural; Killer Cells, Natural - drug effects; Killer Cells, Natural - metabolism; Leukocytes; Lymphocytes; metabolism; Middle Aged; Natural killer cells; Neutrophils; Nutritional Immunology; nutritive value; Oxidation; phagocytosis; Phagocytosis - drug effects; pharmacology; Physical Fitness; Physical Fitness - physiology; physiology; phytochemicals; Plant Extracts; Plant Extracts - pharmacology; Quercetin; Quercetin - blood; Quercetin - pharmacology; Respiratory Burst; Respiratory Burst - drug effects; vegetables; Vertebrates: anatomy and physiology, studies on body, several organs or systems; women; Finland; Immune function; Natural killer cells; Quercetin; Neutrophils; Human; Granulocyte; Natural killer cell; Vertebrata; Mammalia; Female; Neutrophil; Supplementation; Phagocytosis
• ISSN: 0007-1145; 1475-2662; 1475-2662
• DOI: 10.1017/S000711451000156X

Quercetin, a flavonoid found in fruits and vegetables, is a strong antioxidant with anti-inflammatory, antimicrobial and immune-modulating properties. The purpose of the present study was to investigate the effects of long-term quercetin supplementation on innate immune function and inflammation in human subjects. Female subjects (n 120; aged 30–79 years) were recruited from the community and randomised to one of three groups, with supplements administered using double-blinded procedures: 500 mg quercetin/d (n 38), 1000 mg quercetin/d (n 40) or placebo (n 42). Subjects ingested two soft chew supplements twice daily during the 12-week study period. Fasting blood samples were obtained pre- and post-study and were analysed for plasma quercetin, IL-6, TNF-α and leucocyte subset cell counts. Natural killer cell activity (NKCA) and lymphocyte subsets were assessed in a subset of seventy-four subjects. Granulocyte oxidative burst activity (GOBA) and phagocytosis were assessed in sixty-four subjects. Eighteen subjects had overlapping data. Quercetin supplementation at two doses compared with placebo increased plasma quercetin (interaction effect; P < 0·001) but had no significant influence on blood leucocyte subsets, plasma IL-6 or TNF-α concentration, NKCA, GOBA or phagocytosis. NKCA was inversely correlated with BMI (r − 0·25; P = 0·035) and body fat percentage (r − 0·38; P = 0·001), and positively correlated with self-reported physical fitness level (r 0·24; P = 0·032). In summary, results from the present double-blinded, placebo-controlled, randomised trial indicated that quercetin supplementation at 500 and 1000 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.