Encyclopedia · supplement
Spermidine
A natural compound sold as a longevity supplement lengthened human hair follicles grown in a dish at tiny concentrations, but nobody has shown it grows hair on a head.
What it is
A polyamine found in wheat germ, soy and aged cheese and made by every cell. It is sold as an oral supplement and is not approved for any hair use.
How it works
Fast-growing tissues need polyamines. In cultured human scalp follicles, spermidine promoted shaft elongation, prolonged the growth phase and raised the stem-cell-linked keratins K15 and K19. Blocking the polyamine-making enzyme ODC lowered K15, suggesting polyamines support follicle stem cells. Ramot 2011
What the studies show
- Spermidine at 0.1-1 micromolar lengthened shafts and prolonged growth in donor follicles in culture. The authors had consulted for a company that markets hair products. Lab only. Ramot 2011
- Polyamines have a defined distribution in rat follicles (we read only the title). Yamamoto 2018
- No human oral or topical hair trial was found (PubMed search 2026-10-10).
How it's used in studies
0.1-1 micromolar added to culture medium. Oral supplement doses have not been tested for hair.
Side effects and safety
A dietary compound; safety data beyond hair are outside this page.
Bottom line
A cell-culture result only. Fine as a fun fact, not a hair plan.
Fun facts
- A longevity supplement also lengthened human hair follicles grown in a dish. Ramot 2011
Studies 2
Ramot Y et al. Spermidine promotes human hair growth and is a novel modulator of human epithelial stem cell functions. PLoS One. 2011
Tested: spermidine 0.1-1 micromolar
Result: Promoted shaft elongation, prolonged anagen and changed stem-cell marker expression; authors had consulted for a hair-product company.
Read the study ↗Yamamoto Y et al. Spermine, spermidine, and putrescine in rat hair follicle. Histochem Cell Biol. 2018
Result: Polyamines have a defined distribution in rat follicles (title only read).
Read the study ↗Related
- NAD+ precursors (NMN, nicotinamide riboside)The headline anti-ageing supplements have exactly one hair paper, in DHT-treated mice and cells, and no human hair trial.
- Adenosine (topical)Adenosine, a natural signalling molecule, is the cosmetic hair active with the cleanest small placebo-controlled trials, mainly making thin hairs thicker.
- Caffeine (topical)Caffeine in shampoos and leave-on liquids clearly stimulates hair follicles in the lab, but the human trials are small, mostly industry-run and mostly on blends.