34 trials, 8,526 people. Zinc does not stop you catching a cold. It may shorten one by two days at low certainty — and the only moderate-certainty treatment finding in the whole review is that it causes more side effects.
Beetroot juice lowers blood pressure across 22 randomised trials. But juices with more nitrate produced smaller effects, and isolated nitrate supplements moved nothing at all — which is a problem for what the label says is doing the work.
Seven trials, 608 women. Creatine added 0.8 lb of lean mass over a median of nine months — and 16.5 lb to a leg press. Across 684 trials, placebo groups often reported side effects at least as often.
Four prospective studies looked for a link between electrolyte loss and cramp and did not find one. Sodium does help you retain fluid — that part is real, and it was measured in twenty-four people.
Thirteen trials have measured what bovine colostrum does to human body fat. One found a reduction — 0.4%, on 60 grams a day. The reviewers rate the whole body of evidence very low, and every non-randomised study was at critical risk of bias.
Krill oil costs more because it is supposed to absorb better. Across 64 randomised trials it produced no different result on any blood lipid — and the study the whole claim rests on had twelve men and a result that was not statistically significant.
Across 49 randomised trials, protein supplementation added 0.66 lb of fat-free mass. Real, and a fraction of what the tub implies. Without resistance training, two separate meta-analyses find it does nothing at all.
Eleven randomised trials found red light took nearly three inches off the waist and 7.8 lb off the scale — while the percentage of the body that was fat did not change at all. The reviewers grade their own evidence very low to moderate.
Cortisol is not a toxin that accumulates — when someone genuinely has too little, the treatment is 15 to 25 mg of hydrocortisone a day. The predecessor idea, adrenal fatigue, was reviewed across 3,470 articles and called a myth.
Two meta-analyses pooling 45 randomised trials found collagen improves skin hydration and elasticity against placebo. Half the trials in the larger one had missing outcome data, and 95% of participants were women.