Chromium yeast is a supplement that provides chromium, an essential trace mineral, in a bioavailable form by incorporating it into yeast. The scientific rationale for its use in metabolic syndrome is based on chromium's role in modulating carbohydrate and lipid metabolism. Chromium is thought to enhance insulin sensitivity and improve glucose utilization, which are key factors in metabolic syndrome—a cluster of conditions including insulin resistance, hyperglycemia, dyslipidemia, and abdominal obesity.

Several randomized controlled trials and meta-analyses have investigated chromium supplementation (often as chromium picolinate, but sometimes as chromium yeast) in populations with type 2 diabetes or metabolic syndrome. Results are mixed: Some studies report modest improvements in fasting blood glucose and insulin sensitivity, while others find little or no effect. The efficacy appears to depend on baseline chromium status, dosage, and the form of chromium used. A 2014 meta-analysis (Balk et al., Diabetes Care) concluded that chromium supplementation produced small reductions in fasting glucose and HbA1c, but the clinical significance was limited and evidence quality was moderate.

There is no strong historical or traditional use of chromium yeast specifically for metabolic syndrome, as its use is rooted in more contemporary nutritional science. Overall, the scientific evidence for chromium yeast in managing metabolic syndrome is limited and inconsistent, warranting a moderate evidence rating of 2 out of 5.