Carnosine

Glutathione is the body's main intracellular antioxidant, a tripeptide of glutamate, cysteine, and glycine (often written GSH). It is sold as oral, IV, topical, and inhaled products and marketed for everything from detox and immune support to skin lightening, but its real, evidence-backed role is as a redox buffer that neutralizes oxidative stress and supports liver detoxification. Some clinical evidence exists for specific uses, while many popular claims, especially IV skin whitening, rest on weak or risky data.

NAD+ is not a peptide at all, it is a coenzyme every cell uses to move electrons around during energy production. It gets grouped with peptides because it is sold in the same places and injected the same way. Levels fall with age, which is the entire basis of the longevity interest, but the leap from that observation to injecting it is longer than most sellers admit.

DSIP, or delta sleep-inducing peptide, is a small naturally occurring nonapeptide (sequence Trp-Ala-Gly-Gly-Asp-Ala-Ser-Gly-Glu) first isolated in the 1970s from the blood of sleeping rabbits. As the name suggests, it was named for its ability to promote delta-wave (deep, slow-wave) sleep in animals. Despite five decades of study it has no regulatory approval and the human evidence for it as a sleep aid is weak and inconsistent.

Humanin is a 24-amino-acid peptide encoded inside mitochondrial DNA (in the 16S rRNA gene), discovered in 2001 and named for its ability to protect human neurons from Alzheimer-related cell death. It was the first member of the mitochondrial-derived peptide family and is studied mainly for neuroprotection, cell survival, and metabolic and age-related disease. The honest status: it has the deepest preclinical evidence base of any mitochondrial peptide, but human therapeutic trials are essentially absent.

NAD+ precursors are not peptides. They are small molecules, mainly nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN), that the body converts into NAD+, a coenzyme every cell needs to make energy and run repair enzymes. NAD+ falls with age, so these precursors are sold as anti-aging and metabolic supplements. Human trials confirm they reliably raise blood NAD+ levels, but clear proof of real health benefits in people is still missing.

SS-31 (sequence D-Arg-Dmt-Lys-Phe-NH2), known generically as elamipretide and sold as FORZINITY, is a synthetic tetrapeptide that homes in on the energy-producing machinery inside your cells. It works by binding cardiolipin, a fat unique to the inner mitochondrial membrane, to help mitochondria run cleaner and make more ATP with less oxidative damage. This is the rare research peptide with a real regulatory finish line: the FDA granted it accelerated approval in September 2025 for Barth syndrome, though it has failed several other major trials.