Arabinogalactan is a polysaccharide found in a variety of plants, notably in larch trees (Larix spp.), and is marketed as a prebiotic fiber with purported immune-supportive properties. Its connection to Peyer’s patches—the lymphoid follicles in the small intestine that play a critical role in immune surveillance—is based on preclinical and limited human research suggesting that arabinogalactan can modulate immune responses, particularly within the gut-associated lymphoid tissue (GALT), of which Peyer’s patches are a part.

Animal studies have shown that orally administered arabinogalactan can increase the size and activity of Peyer’s patches, stimulating the production of immunoglobulins such as IgA. Some in vitro and animal models suggest that arabinogalactan may act as an immunomodulator by promoting the activity of dendritic cells and macrophages in the gut, which interact with Peyer’s patches. However, human clinical evidence is limited. A small number of studies have reported enhancements in certain immune parameters (e.g., increased antibody response to vaccines) in healthy adults consuming larch arabinogalactan, but these do not directly measure activity specific to Peyer’s patches.

In summary, while there is a plausible mechanistic basis and some early-stage data supporting the use of arabinogalactan to support intestinal immune function (including the potential involvement of Peyer’s patches), the clinical evidence in humans is modest and indirect. Thus, scientific rationale exists, but it is not strong and warrants further research.