Saw Palmetto is a supplement which is derived from the fruit of the plant Serenoa repens. The supplement (saw palmetto) has a caloric value, as it is rich in fatty acids.

Compounds in saw palmetto have the ability to block an enzyme that converts testosterone into dihydrotestosterone (DHT), the latter of which is more androgenic and can cause hair loss in the genetically susceptible. A couple of preliminary studies suggests supplementation with saw palmetto can promote hair regrowth, though more research is needed before strong conclusions can be made.

Saw Palmetto's effects on DHT production have also led to saw palmetto being used for benign prostatic hyperplasia (BPH) and lower urinary tract symptoms in men. Some studies have shown positive results, but larger and more well-designed studies have brought its efficacy into question.