Acknowledgments

To the people who did the actual work

Every fact in this book was established by somebody else — usually slowly, usually with public money, usually without recognition. It seems worth naming what was inherited.

To the Toronto group of 1921–22 — Banting, Best, Macleod, and Collip — who took a pancreatic extract from an idea to a dying child in under two years, and then sold the patent for a dollar. Every peptide drug that followed is standing on that. Chapter 11 tries to do it justice.

To Vincent du Vigneaud, who determined the structure of oxytocin and then synthesized it, proving that a hormone was a chemical you could build rather than only a thing you could extract. Nine amino acids, and the whole idea of peptide therapeutics starts there.

To Bruce Merrifield, whose insight — anchor the growing chain to a solid bead so you can wash everything else away — turned peptide synthesis from a career into a procedure. Nearly every compound discussed in this book, legitimate and otherwise, exists because of a method published in 1963.

To the endocrinologists and physiologists who spent the 1960s through the 1990s working out the incretin effect, the hypothalamic-pituitary axes, and the appetite circuitry, mostly without any prospect that it would ever produce a blockbuster drug. The GLP-1 story is a forty-year basic-science investment that happened to pay off spectacularly, and the people who made it were not the people who got famous for it.

To the participants in clinical trials. Tens of thousands of people took an experimental compound, submitted to the blood draws and the questionnaires and the four-year follow-up, and accepted a real chance of being randomized to placebo. Every ✅ in this book was purchased with their time and their risk. That includes the trials that failed, which are the ones this book has learned the most from.

To the people who published null results, and to the journals that accepted them. A field that only publishes what worked is not a field; it is a marketing department with citations. The negative oxytocin trials, the failed NK1 antagonist program, the myostatin inhibitors that raised muscle mass and did not improve function — those results cost careers and taught more than most successes.

To the skeptics and the replicators

To the researchers who tried to reproduce a striking result and reported honestly that they could not. To the meta-analysts who pooled twenty small trials and found the effect shrinking as the studies got better. To the statisticians who keep insisting that a relative risk reduction without an absolute one is a half-truth.

This work is thankless, structurally underfunded, and frequently unwelcome. It is also the only reason anyone can trust anything. A large fraction of this book's ability to say "that claim doesn't hold up" traces to people who did the unglamorous work of checking.

To the readers this book was written for

To the person who typed "what is BPC-157" into a search bar, spent forty minutes reading contradictory forum posts and three sales pages, and came away less certain than when they started — this book exists because that experience is unacceptable and entirely fixable.

To the person whose sister started Ozempic and who wants to understand it well enough to be useful to her.

To the clinician who has had the same conversation eleven times this month and does not have twenty hours to go read the secretagogue literature.

To the person who already has a vial in the refrigerator, who has probably been talked down to by every authoritative source they consulted, and who deserves accurate information rather than a lecture.

The book is for all four of you, and the effort to serve all four at once shaped nearly every decision in it.

On what this book gets wrong

Some of it is wrong. That is not modesty; it is arithmetic.

A book that makes hundreds of specific claims about an actively moving field will contain errors of three kinds. There will be facts that were wrong when written, which are the author's fault and which corrections are genuinely welcome. There will be claims that were right in 2026 and are wrong by the time you read this, because trials read out, approvals happen, shortages resolve, and a ❌ becomes a ⚠️ the moment somebody finally runs the study. And there will be judgment calls that reasonable experts would make differently — several ratings in these pages are defensible rather than obvious, and the book tries to say so where that is the case.

The third kind is the reason every rating in this book comes with a what would change my mind line. A verdict you cannot imagine revising is not a scientific judgment. If the book has done its job, a reader who disagrees with a rating will be able to say precisely which evidence they weigh differently and why — which is a much better outcome than agreement.

Corrections are wanted. The contribution guide explains what is most useful: a wrong fact with a source, a trial that has since completed, a rating that should move. Evidence updates are the most valuable contribution anyone can make to a book like this, and they are the reason it is licensed the way it is.

On the license

This book is CC BY-SA 4.0: free to read, free to copy, free to translate, free to teach from, free to build on — commercially or otherwise.

There is one request that the license cannot enforce and that is made here instead. If you adapt or redistribute this book, carry the evidence ratings and the safety framing forward intact. Stripping the ⚠️ and ❌ ratings out of a peptide chapter in order to sell a product would be perfectly legal under this license and a complete betrayal of why it was written.

The ratings are the book. Everything else is scaffolding around them.

And finally

To anyone who has ever said "I don't know, and here's what we'd need to find out" in a room where that was the unpopular answer: this book is an extended attempt to make that sentence sound like what it actually is, which is the most rigorous thing a person can say.

DataField.Dev, 2026