Other

A lab-made copy of a natural thymus-gland peptide that fine-tunes the immune system. It is a licensed prescription medicine in many countries (as Zadaxin) but not in the UK, where it is sold only as an unlicensed research chemical.

Grade B · Human trials exist but are incomplete.

A brain peptide discovered in sleeping rabbits in the 1970s and tested as a sleep aid in humans, but development stalled and it never became a licensed medicine.

Grade C · Some human data, far from settled.

An experimental peptide that kills the blood vessels feeding fat tissue, with striking results in mice and a few monkeys.

Grade D · No meaningful human evidence yet.

A lab-made three-amino-acid peptide claimed to protect brain cells. The evidence is almost entirely from cell dishes and rodents, produced by one research group, with no proper human trials.

Grade D · No meaningful human evidence yet.

A natural zinc-dependent thymus hormone that helps immune cells mature, sold as a research peptide despite almost no convincing human trial evidence as a treatment.

Grade D · No meaningful human evidence yet.