Evidence and Sources Policy

This page defines what counts as a credible source on The Health Primer and how we assign our Evidence Level ratings.

Source hierarchy

We prioritize, in descending order: primary peer-reviewed research; recognized health authorities and government health bodies; manufacturer-disclosed data (clearly labeled as such, and weighted accordingly); and reputable secondhand summaries of the above, used only to aid explanation, never as a standalone basis for a claim.

How Evidence Level is assigned

We rate evidence on a five-point scale — Strong, Moderate, Preliminary, Limited, or Insufficient/Unknown — and always separately for the specific product versus its individual ingredients. Product-specific evidence means a study of the finished formula itself. Ingredient-level evidence means research on a component at a comparable dose, which is far more common and is never presented as equivalent to a product-specific finding.

How often sourcing is rechecked

Reviews display a Last Reviewed date. When a product’s formulation, marketing claims, or the underlying research picture changes materially, we recheck and update the relevant content.

What we don’t do

We do not present ingredient science as proof a finished product works. We do not imply diagnosis or treatment of any medical condition. We do not use a study’s existence as evidence of a specific effect size unless the study actually supports that magnitude of claim.