Saccharomyces Cerevisiae (Baker's/Brewer's Yeast) for Immune Function

Research suggests that beta-glucans derived from Saccharomyces cerevisiae — particularly yeast cell wall preparations — may support immune function, with the strongest evidence coming from several randomized controlled trials showing that supplementation can help counteract the temporary immune suppression that follows intense exercise, as measured by markers including circulating monocyte levels, salivary IgA antibodies, reduced cold and flu symptom days, and changes in innate immune gene expression. Studies indicate that the immune-activating properties of yeast beta-glucans appear to depend significantly on cell wall structure, as laboratory and animal research demonstrates that greater surface exposure of beta-glucans produces stronger immune cell activation, a finding supported by both engineered yeast strain studies and oyster feeding experiments. The broader evidence base is mixed in places, however, as one review notes that not all yeast-derived beta-glucans behave the same way — zymosan, for instance, may actually promote harmful inflammatory processes in bone — and a separate body of research raises the possibility that immune responses to yeast mannan proteins could contribute to autoimmune conditions through molecular mimicry, with elevated anti-yeast antibodies appearing in patients with Crohn's disease, lupus, and rheumatoid arthritis. Most of the human evidence is limited to exercise contexts and relatively short supplementation periods, laboratory findings have not consistently translated to clinical outcomes, and rare cases of genuine yeast food allergy have been documented, so the overall picture, while promising for immune readiness, remains incomplete.