Supplementation with aged garlic extract improves both NK and γδ-T cell function and reduces the severity of cold and flu symptoms: A randomized, double-blind, placebo-controlled nutrition intervention

Summary Background & aims Earlier 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. Methods A 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. Results After 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