• Meri P Nantz, Cheryl A Rowe, Catherine E Muller, Rebecca A Creasy, Joy M Stanilka, and Susan S Percival.
• Food Science and Human Nutrition Department, University of Florida, Box 110370, Gainesville, FL 32611, USA.
• Clin Nutr. 2012 Jun 1; 31 (3): 337-44.

Background & AimsEarlier studies show that dietary bioactive compounds can modify proliferation of γδ-T cells. Garlic contains numerous compounds that have this potential and, in addition, has been shown to influence NK cell function. Our primary aim was to demonstrate that aged garlic extract could modify these immune cells.MethodsA randomized, double-blind, placebo-controlled parallel intervention study recruited 120 healthy subjects (60 per group) to determine the effect of aged garlic extract supplementation (2.56 g/d) on immune cell proliferation and cold and flu symptoms.ResultsAfter 45 d of consuming an encapsulated aged garlic extract, γδ-T cells (p = 0.039, n = 56) and NK cells (p = 0.043, n = 56) were shown to proliferate better compared to placebo. After 90 d of supplementation, illness diary entries showed that the incidence of colds and flu, a secondary outcome, were not statistically different; however, the group consuming the aged garlic extract appeared to have reduced severity as noted by a reduction in the number of symptoms reported (21% fewer, p < 0.001, z-test of proportions), a reduction in the number of days (61% fewer, p < 0.001, z-test) and incidences (58% fewer p < 0.001, z-test) where the subjects functioned sub-optimally and the number of work/school days missed due to illness (58% fewer, p = 0.035, z-test).ConclusionsThese results suggest that supplementation of the diet with aged garlic extract may enhance immune cell function and that this may be responsible, in part, for reduced severity of colds and flu.Copyright © 2011 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.

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