Animal studies vs human trials: how much should you trust them?

Most peptides sold online have been studied in cells or animals, and few have been studied in controlled human trials. That difference is the single most useful thing to check before reading anything else about a peptide.

The levels of evidence, from weakest to strongest

1. In vitro (cell culture). Shows that something can happen in a dish. Says little about a whole body.
2. Animal studies. Show an effect in a living animal, usually rats or mice, often at doses and routes that do not map onto people.
3. Case reports and small uncontrolled human studies. Show that people tried it and what was observed, without a comparison group.
4. Randomised controlled trials (RCTs). Compare the treatment against placebo or another treatment in people, assigned at random. This is the level regulators rely on.

Why animal results often fail in humans

Animals differ from people in metabolism, body size, lifespan and how injuries heal. Many compounds that work in animal models never show the same benefit in human trials. A strong animal result is a reason to run a human trial, not a substitute for one.

Questions to ask of any study

• Was it done in people? How many?
• Was there a control group, and was assignment random?
• Who paid for it, and who ran it?
• Has another, independent group found the same result?

Every entry in the Upzo study library is labelled with its design and species for this reason.