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: no effect on dying or on cardiovascular events, at high certainty. The benefit that is real needs 4 grams a day. And omega-3 raised atrial fibrillation risk 25% across 81,210 patients.
A 790-man NIH trial and an individual-participant meta-analysis of 35 trials both find real improvement in sexual function and quality of life. The trial designed to test energy found nothing. And the only trial big enough to count fractures found 43% more of them.
Twelve men trained both arms for 15 weeks, one arm in a bath of exercise-induced testosterone and growth hormone. The hormone-free arm grew 12%. The hormone-bathed arm grew 10%. Replicated in 49 trained men and 56 more.
Researchers pulled the 37 ingredients out of the 32 best-selling testosterone and ED supplements and found 105 trials — but “no whole supplement products have published RCT evidence.” And 91% of the five-star libido reports vanished when the reviews were filtered.
Of 3,334 men, 277 had a normal total testosterone and a low free testosterone — and they had the symptoms. Ninety-six had the reverse, and did not. Plus why the free number on your report was probably calculated with an equation its own field calls faulty.
Across 44 studies, losing weight by diet raised total testosterone about 72 ng/dL and bariatric surgery about 208. Vitamin D did nothing. The famous sleep-deprivation figure rests on ten men and a p-value of .049.
The harmonised normal range is 264 to 916 ng/dL — the man at the top has three and a half times the man at the bottom. Applied properly by age, the cutoff for a 27-year-old is 413, not 300. And in 197,883 men, time of day moved the number more than decade of life did.
The US military now screens every service member over 30. The Endocrine Society’s guideline recommends against routine screening of men in the general population, at its strongest grade. And a glucose drink pushed 15% of men with normal testosterone into the hypogonadal range.
The review that pooled both found cortisol fell significantly and perceived stress did not move at all. Sleep is the best-supported claim, testosterone rises in men but not women, and 25 cases of liver injury have been published worldwide.