Despite the widely accepted concept that probiotics confer miscellaneous benefits to hosts, the controversies surrounding these health-promoting claims cannot be ignored. These controversies hinder development and innovation in this field. To clarify the effects of age and gender on probiotic-induced immune responses, we recruited 1613 Taiwanese individuals and calculated the ratio of IFN-gamma to IL-10 production after each individual's PBMCs were stimulated by six probiotic strains (L. paracasei BRAP01, L. acidophilus AD300, B. longum BA100, E. faecium BR0085, L. rhamnosus AD500 and L. reuteri BR101). Our results indicated that gender and age have only minor effects on the immune modulation of probiotics. Additionally, we showed that L. paracasei BRAP01 and L. acidophilus AD300 are the two dominant strains inducing IFN-gamma/IL-10 production in Taiwanese individuals and that L. reuteri BR101 was the most effective stimulator of IL-10/IFN-gamma. Additionally, a significant inverse relationship between the ability of L. paracasei BRAP01 and L. rhamnosus AD500 to stimulate IFN-gamma/IL-10 or IL-10/IFN-gamma production was also observed. Our results indicated that age and gender have only minor effects on the immune modulation abilities of probiotics.