Zinc yeast is a form of nutritional supplement in which zinc, an essential trace mineral, is bound with yeast (typically Saccharomyces cerevisiae). The rationale for its use in supporting the brain-body system primarily stems from zinc's well-established biological roles. Zinc is crucial for numerous enzymatic reactions, neurogenesis, synaptic plasticity, and neurotransmitter function in the central nervous system. Deficiency in zinc has been linked to cognitive impairment, mood disorders, and delayed neurodevelopment, particularly in children and the elderly.

Scientific studies indicate that adequate zinc levels are associated with healthy brain function. Supplementation can improve cognitive performance in zinc-deficient populations and may help modulate symptoms of depression. However, specific clinical trials using zinc yeast (as opposed to other zinc salts) for direct brain health outcomes are limited. The yeast matrix is thought to enhance zinc's bioavailability, but more direct evidence comparing different forms of zinc on neurological outcomes is needed.

Overall, while there is solid scientific rationale and indirect evidence supporting zinc supplementation for brain health, the use of zinc yeast specifically is justified more by its bioavailability rather than unique cognitive benefits. Thus, the evidence for zinc yeast's efficacy in supporting the brain-body system can be considered moderate.