Sauna & Longevity: The Promise and Perils of Heat ExposureSauna use has been practiced for centuries across cultures-but can deliberate heat exposure meaningfully influence health and longevity?Sauna & Longevity offers a careful, evidence-aware examination of heat as a physiological stressor, exploring how the human body responds to elevated temperature at the systemic and cellular level. Rather than promoting sauna as a cure or optimization strategy, this book approaches heat exposure as a stimulus-one that activates adaptive pathways while also introducing real and measurable limits.Drawing from observational research, stress physiology, and longevity science, the book examines how heat affects circulation, metabolism, cardiovascular demand, and cellular stress responses such as heat shock protein activation. It explores why sauna has become central to modern longevity discussions, while clearly distinguishing biological plausibility from proven long-term outcomes. Throughout, association is separated from causation, and enthusiasm is tempered with scientific restraint.The book also addresses what is often minimized in popular discourse: risk, variability, and context. Individual differences in health status, hydration, cardiovascular function, recovery capacity, and exposure patterns are examined alongside cultural and ethical considerations. Modern wellness hype, biohacking narratives, and the tendency to convert emerging science into prescriptive protocols are critically evaluated.Rather than offering instructions or recommendations, Sauna & Longevity emphasizes interpretation. It invites readers to understand what the research suggests, where uncertainty remains, and why heat exposure cannot be reduced to universal benefit or harm. Sauna is framed not as a solution, but as a tool-one that interacts with complex systems and demands careful consideration.This book serves as Volume Three of The Promise and Perils series, which examines emerging compounds, practices, and interventions through a clear-eyed lens-separating biological promise from scientific uncertainty. Earlier volumes explore synthetic peptides (BPC-157) and pharmaceutical longevity interventions (Rapamycin). Together, the series encourages curiosity without certainty, engagement without obligation, and understanding without illusion.