The fruit of the serenoa plant, often used as an herbal treatment for a variety of urinary conditions including benign prostate hyperplasia (also known as BPH, an enlargement of the prostate common in older men).

However, clinical trials indicate that saw palmetto is probably no more effective at treating BPH than a placebo. The fruit’s extract may contain enzymes that affect the body’s ability to process sex hormones, including testosterone, but there is currently limited research for this use. As saw palmetto extract also includes phytosterols, a type of plant steroid compound, it may lower cholesterol levels when taken regularly.

As a supplement, saw palmetto is considered safe. The most common side effects include upset stomach and other mild gastrointestinal issues.