Saw palmetto (Serenoa repens) is a tree that grows up to 10 feet tall with thorn-shaped leaves arranged like a fan. Its ripe fruit is used to make medicine.
Saw palmetto seems to lower the amount of pressure on the tubes that carry urine in males. Saw palmetto also might prevent testosterone from being converted to a more potent form called dihydrotestosterone (DHT). Reduced levels of DHT might help prevent some types of hair loss.
People commonly use saw palmetto for symptoms of an enlarged prostate called benign prostatic hypertrophy (BPH). But it doesn't seem to improve this condition. Saw palmetto is also used to prevent complications from prostate surgery and for treating other prostate conditions, male-pattern baldness, sexual dysfunction, and many other purposes, but there is no good scientific evidence to support most of these uses.