How to Evaluate Peptide Evidence

Not all evidence is created equal. The hierarchy, from strongest to weakest, generally follows this pattern: systematic reviews and meta-analyses of randomized controlled trials (RCTs), individual RCTs, observational studies, animal studies, in vitro (cell culture) studies, and mechanistic reasoning. Many peptides have strong animal evidence but limited human data. This is an important distinction — what works in mice does not always work in humans, and side effects can differ dramatically between species.

Throughout this resource, we use five evidence levels: Strong (supported by multiple human clinical trials), Moderate (some human data with consistent preclinical support), Emerging (early human data or strong animal evidence), Preliminary (mostly preclinical with limited human data), and Limited (very early research, mostly mechanistic). These ratings reflect the overall body of evidence, not just the most optimistic study. We aim to be conservative in our assessments.

Be cautious of claims that: cite only animal studies as proof of human efficacy, cherry-pick positive results while ignoring negative studies, use phrases like 'clinically proven' without specifying the clinical context, promise dramatic results with no mention of limitations, or fail to acknowledge unknowns and risks. Good science is transparent about what it does and does not know. Any resource that presents peptides as guaranteed solutions without acknowledging uncertainty should be viewed skeptically.

For each peptide, we provide: an evidence snapshot showing the strength of human, animal, and mechanistic evidence; specific evidence ratings for each claimed use case; clear statements about what is unknown; and links to key references. We encourage you to use this information as a starting point for informed conversations with qualified clinicians, not as a substitute for professional medical guidance.