Tim Kennedy on health: what the evidence says · JRE #2055
SUBJECT: HEALTH
Not a true/false call. Every claim is logged with its sources; read the exhibits below.
Because what happens is your endorphins, your dopamine ramps up by 200% naturally in a healthy way. It makes you nicer to people that you run into.
What the evidence says 01 / RECORD
The commonly cited figure traces to a small 2000 study (Sramek et al., European Journal of Applied Physiology) in which young men immersed for one hour in 14C water showed plasma dopamine rise by about 250% and plasma noradrenaline rise by about 530%, alongside a 350% increase in metabolic rate and modest increases in heart rate and blood pressure. Kennedy's "200%" is in the right range for that single acute-exposure finding, though it understates the study's own figure (250%) and omits the much larger noradrenaline increase, as well as the fact that the effect was measured after prolonged immersion in very cold (14C) water rather than the shorter cold-plunge protocols typical of consumer use. A 2025 review of cold-water therapy research (Kunutsor, Lehoczki, Laukkanen, GeroScience) cites this same 250% dopamine figure as one data point supporting possible mood and alertness benefits of cold exposure, but the review is upfront that evidence for cold-water immersion's psychological effects remains limited, drawn largely from small acute studies rather than large controlled trials establishing lasting mood or behavioral effects. No peer-reviewed source located compares this dopamine rise to MDMA or supports the claim that it reliably makes people "nicer" to others; those framings are not supported by the cited physiology research.