Hotwired review explores health ideas about sweat

Bill Gifford's Hotwired examines human sweating and its evolutionary role, and cites studies that link heat exposure and sauna use to cardiovascular, cellular and mood-related findings.

Bill Gifford's Hotwired examines sweating, heat exposure and their possible health links. The book combines evolutionary background, reporting on laboratory and field experiments, and summaries of clinical research. Gifford also includes first-person accounts of heat training and endurance events. The narrative notes both potential benefits and safety concerns. Key points: - Humans have about two to four million eccrine sweat glands concentrated on hands and feet, and eccrine glands cool the body by evaporation. - The book presents an evolutionary view, drawing on David Carrier's work, that sweating enabled sustained exertion in hot conditions and supported persistence hunting. - Gifford cites studies, including work by a Finnish cardiologist, that associate regular sauna use with lower risks of heart attack, stroke, hypertension, Alzheimer's disease and overall mortality. - Researchers discussed in the book describe how heat stress triggers heat-shock proteins that help repair cellular proteins and may affect conditions such as nonalcoholic fatty-liver disease. - The author reports research linking heat treatments — including hot-yoga, infrared saunas and hot-water immersion — with reductions in measures of depression in some studies. - The book covers safety issues, including hyponatremia linked to excessive water intake during endurance events and heat illness risks in football preseason practice, noting 2011 high-school deaths and subsequent safety guideline changes in Georgia. Summary: Hotwired collects evolutionary, clinical and personal reporting to present multiple lines of research connecting heat exposure to cardiovascular, cellular and mental-health topics and to note related safety concerns. Undetermined at this time.