Finnish men who took 4–7 saunas a week had a 63% lower adjusted risk of sudden cardiac death, a figure resting on 201 men and 10 deaths. Then 20 randomised trials of heat, most of them not Finnish sauna, found almost nothing.
Americans search for sleep hygiene well over 100,000 times a month. The insomnia guideline advises clinicians against using it as a standalone treatment — and when 241 trials were pulled apart to weigh each ingredient, it scored 1.01. Nothing.
A month-long trial put box breathing against two other breathing techniques and meditation. All three breathing groups got the same small lift after each session, and smaller studies find the square tying with the alternatives more often than beating them.
Around 117,000 Japanese adults were followed for years, and those who said their life felt worth living were less likely to die. None of those studies used the four-circle diagram, which was first published in 2012 with a different word in the middle: purpose.
A 2025 meta-analysis linked 7,000 steps a day to 47% lower mortality (14 studies) and 38% less dementia (2 studies). For death the curve bends near 5,400 steps; cancer risk did not move. Whether age changes the number is still open.
Two big analyses of the trials found magnesium lowers blood pressure by about 2 to 3 points, mainly in people whose blood pressure is high. For older adults' night leg cramps, Cochrane found nothing. And the headline sleep result, 17 minutes, comes from two small trials.
A 2003 meta-analysis examined 250 supplements; only six had enough studies to analyse and only two worked. Creatine was one. Modern trials put it at about 2.5 lb of extra lean mass in under-50s — and 3 lb in older adults.
Cochrane pooled 86 trials and 162,796 people: little or no difference to dying or to cardiovascular events, at high certainty. The one trial that cut heart events used a 4-gram prescription against a disputed placebo, and the atrial fibrillation risk is clearest at those doses.
Two big trials and a meta-analysis agree that testosterone therapy lifts sex drive in men with confirmed low testosterone; its effects on energy and mood are small. The largest trial found no rise in heart attacks or strokes, but more heart-rhythm problems, lung clots and kidney injury, and the largest trial to count fractures found 43% more of them.
Twelve men trained both arms for 15 weeks, one arm recovering in a bath of exercise-induced testosterone and growth hormone. The arm with no hormone spike grew 12%. The hormone-bathed arm grew 10%. Two larger studies from the same lab found no link with testosterone either.