After the experiment

Less tissue damage, a higher blood measurement and a change in collagen production leave different kinds of evidence behind.

Experimental outcomes

The word recovery can quietly change its meaning between papers. In the stomach experiments it concerns an injury. In the NAD+ trials, the change may be a blood measurement or a particular metabolic response. GHK-Cu adds supporting-material synthesis and small skin studies. I’d distrust any league table pretending these compounds ran the same race.

Subject	Experimental setting	Reported outcome
BPC-157	Rat gastric ulcers	Reduced ulcer area and accelerated tissue rebuilding
KPV	Cell cultures and mouse colitis	Less inflammatory signalling and reduced colitis severity
NMN, a precursor of NAD+	Postmenopausal women with prediabetes	Improved muscle insulin sensitivity; unchanged body composition and HbA1c
GHK-Cu	Small topical study described in a review	Procollagen synthesis increased in a larger share of subjects than in the comparison groups

Reading the procollagen percentages

The skin comparison is easy to misremember. The review reports increased procollagen synthesis in 70% of GHK-Cu subjects, 50% of vitamin C subjects and 40% of retinoic-acid subjects. Each percentage counts subjects with an increase. The height of a bar therefore represents a response frequency within that reviewed study, rather than the amount of collagen made or the amount a wrinkle changed.

I’d need a visible-benefit measurement before trusting a confident cosmetic claim based on those procollagen response proportions. A response measurement can justify a better trial without telling us how much difference a person would notice.

Bars show procollagen increases in seventy, fifty and forty percent of subjects — Subjects showing increased procollagen synthesis in the study described by the 2025 topical-GHK review. These are response proportions, not wrinkle-reduction percentages.

Human benefit and durable recovery

The 2025 NAD+ precursor review found limited human efficacy despite consistent blood increases. The BPC-157 review found a sparse human record. KPV’s published evidence remains in cells and animals, while GHK-Cu’s human work centres on small topical studies. Different gaps remain after each experiment.

The aftermath I care about lasts: a tissue functioning better, a person experiencing a sustained improvement, and harms being counted carefully enough to judge the trade-off. The cited findings leave that larger picture incomplete. The individual chapters supply the context for BPC-157, KPV, NAD+ and GHK-Cu, including the exact substance or combination tested.