Evidence Grading System

ZYNAVA uses a transparent grading system to communicate the strength and quality of available research for each ingredient. Our goal is to help you understand what the science says — and what it doesn't.

How We Grade Evidence

Each evidence grade reflects the volume, consistency, and quality of peer-reviewed research from sources including PubMed, NIH, and PubMed Central (PMC). Grades are not endorsements — they describe the current state of the evidence.

Grade A — Strong Evidence

Multiple well-designed clinical trials, systematic reviews, or meta-analyses support a consistent finding. Results have been replicated across different populations and study designs.

Grade B — Moderate Evidence

Several clinical studies show positive results, but the evidence may be limited by smaller sample sizes, fewer replications, or some inconsistency between studies.

Grade C — Preliminary Evidence

Early-stage research (animal studies, in-vitro studies, or small pilot trials) suggests potential benefits, but human clinical trials are limited or results are mixed.

Grade D — Insufficient Evidence

Very limited or no peer-reviewed research is available. Claims are largely based on traditional use, anecdotal reports, or theoretical mechanisms that have not been tested in rigorous studies.

Important Limitations

  • Evidence grades reflect the current state of research and may change as new studies are published.
  • A high evidence grade does not mean a supplement is right for you. Individual factors like medications, health conditions, and genetics all matter.
  • These grades are not medical recommendations. Always consult with a qualified healthcare provider before starting any supplement.
  • ZYNAVA does not conduct original research. We reference publicly available studies from established databases.

Our Sources

All referenced studies come from trusted, peer-reviewed databases:

  • PubMed — U.S. National Library of Medicine
  • PMC — PubMed Central full-text archive
  • NIH — National Institutes of Health

Disclaimer: ZYNAVA provides educational information only. Evidence grades are not medical advice, diagnoses, or treatment recommendations. Consult a healthcare professional before using supplements. See our full Medical Disclaimer and Editorial Policy.

Last Updated: February 2026