Saw palmetto is a plant. Its ripe fruit is used to make medicine. Saw palmetto is best known for its use in decreasing symptoms of an enlarged prostate (benign prostatic hypertrophy, BPH). According to many research studies, it is effective for this use. Saw palmetto is used for treating certain types of prostate infections. It is also sometimes used, in combination with other herbs, to treat prostate cancer. Some people use saw palmetto for colds and coughs, sore throat, asthma, chronic bronchitis, chronic pelvic pain syndrome, and migraine headache. It is also used to increase urine flow (as a diuretic), to promote relaxation (as a sedative), and to enhance sexual drive (as an aphrodisiac). How does it work? Saw palmetto doesn’t shrink the overall size of the prostate, but it seems to shrink the inner lining that puts pressure on the tubes that carry urine.