How we grade evidence

We start from systematic reviews and meta-analyses, which pool results from many trials, instead of single studies, animal research, or marketing claims. Every claim on this site links to its source on PubMed. Study titles, journals, and years are pulled from PubMed automatically rather than typed in by hand.

Evidence grades

• AStrong evidence Several meta-analyses or large randomized trials agree on a meaningful benefit.
• BModerate evidence Meta-analyses show a benefit, but the trials are small, vary a lot, or the effect is modest.
• CLimited evidence Few or small trials, inconsistent results, or benefit only in specific groups.
• DInsufficient evidence Little good human data, or high-quality trials show no meaningful benefit. We list these so you know what to skip.

What we consider

• Study design and quality (meta-analyses of randomized controlled trials rank highest)
• Consistency of results across studies
• Size of the effect, not just whether it was statistically significant
• Funding source. We note when benefits appear only in industry-funded studies.
• Newer, larger analyses. When an update overturns earlier findings, we follow the update.

Safety information

Side effects, upper limits, pregnancy guidance, and medication interactions come from NIH Office of Dietary Supplements and NCCIH fact sheets and the cited literature. Interaction checks cover common medication classes only and do not replace a pharmacist's review.

How matching works

When you describe a goal, our software first screens your text for urgent warning signs. An AI model then maps your words to the goals we cover. The AI only picks categories. It doesn't write recommendations or invent studies. All results come from our curated, cited database.

Independence

We may earn a commission from purchase links. Commissions never affect grades or ranking order. Rankings are determined only by evidence grade and the number of supporting reviews.

Review status

Each supplement page shows whether its summary is a draft or has been reviewed by a qualified health professional, and when it was last updated.