Early, small, conflicting, or animal-only. Not actionable alone.
Something real does happen: blood levels of the vitamins go up. What has not been shown is that it buys you anything. The biggest brand's own trial ran thirty people for four weeks.
In pooled trials, compression boots ease soreness a little and show nothing clear for strength, power or the blood markers a flush should clear. Most of the trials had no dummy treatment to compare against.
The big gum effect in the 2024 review came from two small trials in 70 children and teenagers. In two eight-week trials in adults, swishing plain water did as much for bleeding gums, and where tooth colour was compared fairly, oil did no better than water.
Honey may ease a child's night cough a little: the review's placebo figure was about twice what its largest trial found, and a 2022 double-blind trial found no difference. Never give honey to a baby under one.
The best result came from 20 people with mild sleep apnea, any blocked nose treated first. The trials since are small and point both ways, and we found no test at all of the jawline promise.
After a 15-minute walk among trees, 585 young men scored 5.2 points lower for tension than after a city walk, and reviews find people report feeling better again and again. Blood pressure and cortisol move only a little, and nobody can be blinded to a forest.
A 2026 review found nine studies of the carnivore diet, two of them meal plans worked out on paper. In both of its surveys that measured LDL before and during the diet, LDL went up: by a typical 36 mg/dL in 14 volunteers' lab reports.
Sixty-three studies tie feeling hooked on your phone to worse sleep. The studies that tested direction found the pull runs both ways, and in small trials, a phone-free bedtime improved people's own ratings of their sleep.
Vitamin D prevents and treats rickets and osteomalacia; that much is settled. The big trials mostly enrolled people who already had enough, and where they looked at the people who started low they mostly found no clear benefit. The official daily figures are 600 IU in the US (800 after 70) and 400 in Britain, with a ceiling of 4,000.
Cochrane's 2024 review: zinc may shorten a cold by about two days, at low certainty, and probably brings more side effects, mostly a bad taste and an upset stomach. On catching fewer colds its trials, mostly in children, found little or no effect. Zinc in the nose is a separate story, with an FDA warning from 2009.