Immunitywell supported · human data
Vitamin D cuts respiratory infection risk, but only if you dose it right
Daily or weekly vitamin D modestly reduced the odds of acute respiratory infections in a large pooled analysis of trial data, while occasional big bolus doses showed no benefit at all. People who started out severely deficient had the most to gain, and no rise in serious side effects was seen.
What it shows: Among the strongest nutrition evidence around: raw data pooled from 25 placebo-controlled trials covering 11,321 people aged 0 to 95, and rated high quality. The catch is that the average benefit was modest, and it disappeared entirely in people given occasional large doses instead of regular ones.Meta-analysis · BMJ