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.
Twenty-three randomised trials pooled together put berberine’s effect on body weight at 1.9 lb. Semaglutide, in the trial that made it famous, took off 33.7. Both numbers come from the best evidence available for each.
The trial behind the 2024 headlines was retracted in September 2025 — four days after a meta-analysis pooled it. Ten months on, that meta-analysis still carries no correction. What survives: a real but modest effect on post-meal blood sugar, and about four pounds in the best weight trial, most of it back within a month of stopping.
Partially hydrogenated vegetable oil genuinely harmed people: when 11 New York counties restricted trans fats, heart attacks and strokes fell an extra 6.2%. That fat is gone. The fear outlived it and reattached to the oil that's left — which is usually soybean, and which the bottle doesn't tell you.
Pooled across 28 randomised trials, eggs raise LDL by 5.55 mg/dL — so 'eggs don't affect your cholesterol' is wrong. But adjust for total dietary cholesterol and the egg association with heart disease vanishes entirely. And two meta-analyses disagree about the one thing the 'it's a wash' argument needs.