Effects of Sauna Bathing on NMR-Based Metabolomic Profiles.

Abstract

BACKGROUND: Frequent sauna bathing is associated with reduced risk of adverse cardiovascular outcomes. However, the biochemical pathways through which sauna bathing may exert its cardiovascular health effects remain unclear. We therefore investigated the effects of Finnish sauna bathing on various blood-based cardiometabolic biomarkers. Specifically, this study investigated how a single 30-minute Finnish sauna session (AS) and an 8-week exercise-plus-sauna intervention (ESS) influence circulating metabolomic biomarkers related to lipid and amino acid metabolism. METHODS: The study included two complementary populations: (1) an acute sauna exposure study including 63 habitual sauna users with at least one cardiovascular risk factor, and (2) an 8-week randomized controlled trial (RCT) including 47 sedentary non-regular sauna users randomized to exercise, exercise plus sauna, and control arms. The exercise intervention consisted of concurrent training three times per week, with the sauna group additionally completing 15 min of post-exercise sauna bathing. Circulating metabolites were quantified using high-throughput 1H-NMR spectroscopy at multiple time points in the acute study and at baseline and post-intervention in the RCT. RESULTS: AS produced consistent metabolic shifts, including significant reductions in concentrations of plasma triglycerides and VLDL particles, decreases in branched-chain and aromatic amino acids, and increases in ketone bodies, suggesting a metabolic pattern compatible with enhanced lipid utilization and a transient metabolic stress response. ESS resulted in additional improvements beyond exercise alone, including reductions in LDL particle number and concentration, greater decreases in VLDL subclasses, and increases in HDL particle size, suggesting additional metabolic effects when heat exposure is added to exercise training. CONCLUSIONS: Sauna bathing, as an example of heat exposure, induces favorable alterations in lipid and amino acid metabolism and when combined with regular exercise, augments longer-term improvements in lipoprotein profiles.

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