How to Read Peptide Studies
A reader’s checklist for assessing whether a peptide paper supports the claim being made about it.
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Study type
- RCT — randomised, controlled, in humans. Strongest individual-study type.
- Human observational — useful for safety signals, weaker for causation.
- Animal — mechanism plausibility; not human-relevant by itself.
- In vitro — mechanism plausibility only.
- Case report — hypothesis-generating, very weak evidence.
Sample size
Larger is generally better, but not always. A well-powered RCT of n=200 beats a poorly-designed RCT of n=2000. Look for whether the study pre-specified the sample size, and whether it was powered to detect a clinically meaningful effect.
Endpoints
Was the primary endpoint pre-registered? Was it a surrogate (e.g. biomarker change) or a clinically meaningful outcome (e.g. tendon re-injury)? Beware studies that report only secondary endpoints, which can be cherry-picked.
Controls and blinding
Was there a control group? Was randomisation concealed? Were outcome assessors blinded? Open-label studies overestimate effect sizes — particularly for subjective endpoints (pain, recovery, well-being).
Conflict of interest
Who funded the study? Who employed the investigators? A manufacturer-funded study is not automatically wrong — but it is a signal to read more carefully and to look for independent replication.
Limitations
Read the limitations section. A study’s authors usually know its weaknesses better than its readers do. A paper that does not discuss its limitations is itself a warning sign.
Relevance
Does the study answer the question being asked of it? A rodent tissue-repair study does not establish a claim about human muscle growth. A 12-week human PK study does not establish a claim about 12-month safety.
See also our companion tool: study quality checklist.