Longevity peptides is a marketing category rather than a pharmacological one, and the molecules inside it have almost nothing in common except the promise attached to them.
That matters because the evidence behind each one is wildly different in quality. Some have randomized trials with hundreds of participants and hard biochemical endpoints; others have a handful of cell-culture papers from a single research group, and are sold on the strength of the mechanism they were named after.
What follows is each compound in that category, with what its human studies measured and where the record stops. A shorter version organized by outcome rather than by molecule is in peptides for anti-aging.
The evidence, compound by compound
| Compound | Strongest human evidence | What it showed | FDA compounding status |
|---|---|---|---|
| NAD+ precursors (NR, NMN) | 33 human intervention studies, 28 randomized | Levels rise reliably; outcome effects heterogeneous and often null | NAD in 503A Category 1 |
| Glutathione | 6-month randomized trial, 54 adults | Body stores up 30 to 35% at 1,000 mg a day; back to baseline after washout | 503A Category 1 |
| GHK-Cu and collagen peptides | Meta-analysis of 26 trials, 1,721 participants | Skin hydration and elasticity improved with hydrolyzed collagen | GHK-Cu Category 1 except injectable routes |
| GHRH analogs | 20-week randomized trial, 152 adults aged 55 to 87 | IGF-1 up 117%, body fat down 7.4%, executive function improved | Sermorelin compoundable; tesamorelin is brand-only |
| Epitalon | Cell-culture and animal work | Telomerase activity in cultured cells | On no 503A list |
| MOTS-c | No human trial identified | Rodent and mechanistic work only | On no 503A list |
NAD+ and its precursors
This is the best-studied entry in the category, and the pattern in it is instructive for everything else. NAD+ is a coenzyme that falls with age, and the reasoning is that restoring it should restore something downstream.
A crossover trial gave nicotinamide riboside to healthy middle-aged and older adults for six weeks and found it well tolerated, with NAD+ metabolism measurably stimulated [2]. The target engagement is real and it replicates.
A 2026 PRISMA-guided systematic review then gathered every human and rodent intervention study from January 2010 to October 2025 [1]. It identified 113 eligible studies: 33 human, of which 28 were randomized, and 80 in rodents.
Its summary of the human work is that oral precursors consistently demonstrated biochemical target engagement and were generally well tolerated over weeks to months, while effects on functional, metabolic and vascular outcomes were heterogeneous and often null.
The same review reports that no eligible outcomes trial evaluated intravenous or intramuscular NAD+ itself for an anti-aging or wellness indication. That is the form most commonly sold in clinics, and it is the form with no outcome evidence, which is covered in NAD injections and their evidence.
Glutathione
Glutathione is the body's most abundant endogenous antioxidant, and the question that dogged it for years was whether swallowing it does anything at all, since it is a tripeptide and the gut digests peptides.
A six-month randomized, double-blind, placebo-controlled trial in 54 non-smoking adults settled the absorption question [3]. At 1,000 mg a day, glutathione rose 30 to 35% in red cells, plasma and lymphocytes, and 260% in buccal cells, all at P < 0.05.
At 250 mg a day the rise was 17% in whole blood and 29% in red cells. Natural killer cell cytotoxicity more than doubled against placebo in the high-dose group at three months.
Two details limit how far that carries. Levels returned to baseline after a one-month washout, so the effect is maintenance rather than repair, and the trial measured stores and immune markers rather than any clinical outcome.
The skin peptides
Copper peptides and oral collagen peptides are sold under the same longevity banner, and their evidence is about skin rather than about aging as a whole.
A meta-analysis of 26 randomized trials covering 1,721 participants found hydrolyzed collagen supplementation significantly improved skin hydration, with an overall effect of Z = 4.49 and P < 0.00001 [4]. Its subgroup analyses found the effect varying by collagen source and by how long supplementation ran.
The authors also identified several biases in the trials they pooled, which is worth carrying alongside the headline. Skin hydration measured over weeks is a genuine endpoint, and it is not a claim about how long anyone lives.
The growth hormone route
GHRH analogs raise growth hormone by acting on the pituitary, and the longevity argument for them starts from the observation that growth hormone output falls steadily with age.
The best-designed trial in this space gave 152 adults aged 55 to 87, 66 of them with mild cognitive impairment, a daily bedtime injection of tesamorelin at 1 mg or placebo for 20 weeks [5].
IGF-1 rose 117% while staying inside the physiological range, body fat fell 7.4%, and the intent-to-treat analysis showed a favorable effect on cognition at P = .03, driven by executive function at P = .005.
Adverse events were reported by 68% of treated adults against 36% on placebo, and fasting insulin rose 35% within the normal range in the group with mild cognitive impairment. The compound used there is brand-only in the United States, so it is not what a compounding pharmacy dispenses.
Sermorelin is the compoundable GHRH analog, and its own trial record is thinner and older than this one.
The two with no human trials
Epitalon, also spelled epithalon, is a four-amino-acid peptide derived from a bovine pineal extract. A 2025 review covering 25 years of work on it describes in vitro, in vivo and in silico studies, and reports effects on melatonin synthesis, interleukin-2 messenger RNA and telomerase activity [6].
The specific telomere claim traces to a 2003 paper reporting telomerase activity and telomere elongation in cultured human somatic cells [7]. A cultured-cell result is a mechanism, not an outcome, and the fuller account is in the epitalon article.
MOTS-c is a mitochondria-derived peptide with rodent and mechanistic work behind it and no identified human trial, which is set out in the MOTS-c evidence article.
Neither appears anywhere in FDA's 503A bulk substances list, in any of its three categories[8]. No human dose is established for either one.
Putting it together
Read as a group, these compounds separate cleanly into three tiers. Two of them reliably move a measurable thing in the body, one improves a skin property, one has a well-run trial with a cognitive signal, and two have no human evidence at all.
None of them has been tested against the outcome the category is named for. That is not a criticism of the trials, which measured what trials can measure; it is a statement about what the category is currently entitled to claim.
To compare prescribers for the compounds that are actually dispensed, see the longevity peptide rankings, and for the rest of the research on this goal, the longevity hub.