Vitamin D3 (Lichen)

High: Consistent benefit across adequately powered, replicated trials.

Twenty-five randomised trials pooled at the level of individual participants rather than published summaries, across 11,321 people. Evidence that is both replicated and adequately powered is what separates High from Moderate. The effect was largest in those who started most deficient, which is the population this is recommended to. This tier rests on respiratory-infection trials, which is the immune half of the stated purpose. The bone-health basis is separate, long settled, and not covered by this citation. The trial evidence covers vitamin D3 without distinguishing its source.

1. 1
   Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data

   BMJ · 2017

   IPD meta-analysis of 25 RCTs and 11,321 participants; daily or weekly dosing reduced acute respiratory infection risk, with the largest effect in participants with baseline 25(OH)D below 25 nmol/L.

Tiers are ExoF's reading of the published literature on Vitamin D3 (Lichen), not a clinical guideline. They describe how well studied an effect is — never how well it will work for you.