Evidence Level
Moderate
Garlic has solid clinical evidence for immune support. Josling (2001) conducted an RCT showing allicin-containing garlic dramatically reduced cold incidence and duration over 12 weeks. Nantz et al. (2012) demonstrated that aged garlic extract enhanced NK cell function and reduced cold severity in a well-designed RCT. The antimicrobial mechanism of allicin — reaction with thiol groups in essential microbial enzymes — has been extensively characterized. Aged garlic extract provides different but complementary benefits through S-allyl cysteine and other stable organosulfur compounds that modulate immune cell function and reduce inflammation.