Bifidobacterium (mixed species) has scientific support for its role in modulating the immune system, including effects on Peyer’s patches, which are important lymphoid tissues in the gut associated with mucosal immunity. Several animal and in vitro studies have demonstrated that supplementation with Bifidobacterium strains can enhance the number, size, or function of Peyer’s patches. These probiotics have been shown to increase secretory IgA production, stimulate dendritic cells, and influence the maturation and activation of immune cells within Peyer’s patches. For example, research published in Clinical and Experimental Immunology and Journal of Dairy Science has documented that Bifidobacterium species can upregulate gut-associated lymphoid tissue responses, partly via their interaction with M cells in Peyer’s patches, leading to improved mucosal immune defense.

However, most of the direct evidence comes from animal models (e.g., mice or pigs) and in vitro studies; human data specifically linking Bifidobacterium supplementation to changes in Peyer’s patch function are limited but suggestive. There are also clinical studies showing general enhancement of gut immunity and reductions in infection risk with Bifidobacterium supplementation, which may indirectly involve Peyer’s patches. Thus, while the mechanistic rationale is strong and supported by preclinical data, direct human evidence is moderate, justifying a rating of 3.