The Library and the Weekly Letter
General information about published research. It describes what sources say. It does not recommend anything.
The library
The library is a set of plain descriptions of the peptides, supplements and other things people track. You can read it in the app and search it when you add something to your list.
- Evidence labels. Claims in an entry carry one of four labels: weak, mixed, moderate or strong, based on the kind of study behind them.
- Regulatory status labels, with a date. Each entry shows its status, for example licensed medicine, investigational, not authorised for any use, supplement or cosmetic ingredient, and the date that status was checked.
- Sources. Entries link to the sources they draw on.
- No doses. The library gives no doses, no recommended amounts and no instructions on how to obtain anything.
A regulatory status label describes what a regulator has said. It is not a recommendation. Some items are not authorised for any use in the UK, and the label says so plainly.
The weekly letter
The letter is a short weekly summary of published studies. It is the same for every reader. Nothing about you or your logs is used to write it. It reports what published sources said and does not recommend anything. The latest four issues are free to read in full. Older issues are Premium, except safety and regulatory items and corrections, which stay open to everyone.
How we choose studies
Where the studies come from
Each week we search public sources only, using a fixed list of topics: PubMed for papers, systematic reviews and guidelines, Europe PMC for abstracts, ClinicalTrials.gov to check how many people a trial enrolled, Crossref to check whether a paper has been retracted, and openFDA for regulator notices.
What gets left out
- Retractions, notices of concern, editorials, comments and news items.
- Studies with no usable abstract, or that describe a trial design without reporting results.
- Studies in animals or cells only. These are never presented as evidence about people.
- Studies rated below Mixed, or below Moderate where a mistake could matter more.
- Anything already used in an earlier issue.
How an issue is balanced
An issue has at most five findings, no more than two from any one topic and no more than one regulator notice. We look for at least one safety, no-effect or regulatory item whenever one is available. Preprints, which have not been peer reviewed, never lead an issue. If a draft cannot pass the automatic checks, the issue is a general explainer instead, and it is labelled as one.
How an issue is written and approved
A draft is written with AI from the abstracts of the chosen studies only, not from full papers. Automatic checks then run: every number in the draft must appear in the cited abstract, the key quote must match exactly, and wording that makes claims, gives doses or mentions buying or prices is blocked. A named person then reads the draft next to its sources, completes a review checklist and approves it. The approver is Alex Prior-Byrne, and every issue is approved by a person before it is published. The reviewer can lower an evidence label but never raise it. Sources are checked again for retractions before approval and on a regular sweep after that.
The evidence labels in the letter
| Label | What it means |
|---|---|
| Strong | A clinical guideline, or a systematic review or meta-analysis of randomised trials. |
| Moderate | A randomised trial of 300 or more people, an observational study of 1,000 or more people, or a systematic review not limited to randomised trials. |
| Mixed | A randomised trial of 50 to 299 people, an observational study of fewer than 1,000 people, or a non-randomised trial of 300 or more. |
| Weak | A small or unknown-size trial, a case report, a narrative review, an unclear design, a mix of people with animals or cells, or a preprint. |
| Preclinical | Work in animals or cells only. It says nothing certain about people. |
Regulatory status lines
Where an item names a medicine or substance, it carries a status line for Great Britain with an as-of date, which a person confirms against the regulator before the issue goes out.
Corrections
If something is wrong, the issue is corrected in place with a dated note at the top. Corrections are never behind the paywall. If an issue cannot be fixed, it is withdrawn and a notice replaces it.
PEPTIDAL sells no products and has no affiliate links. Letter content is published in the app, not on this website. General information about published research. Not medical advice. Talk to your doctor or pharmacist.
Spotted a mistake? hello@getpeptidal.com