Saw palmetto (Serenoa repens or Sabal serrulata) is a dwarf palm plant native to North America. It primarily grows along the Atlantic coast in Georgia and Florida. The active ingredients are believed to be found in the plant's brown-black berries.
Saw palmetto was a popular folk remedy used by Native Americans to treat urinary conditions in men and breast disorders in women.
It has become an accepted treatment for symptoms associated with benign prostate gland enlargement (called benign prostatic hyperplasia, or BPH) in many parts of Europe and in New Zealand. In North America, saw palmetto is considered an alternative herbal remedy for BPH.
Saw palmetto is also popular as an herbal remedy for a type of hair loss and baldness called androgenic alopecia, or male- and female-pattern baldness. This type of hair loss is typically the greatest at the top of the head or around the temples.
Although we still don't know exactly how it works, it's believed that it may block an enzyme (5-alpha-reductase) from allowing the hormone testosterone from being converted to another hormone, dihydrotestosterone. Dihydrotestosterone is considered a key contributing factor to the onset and progression of androgenic alopecia and benign prostatic hyperplasia.
Saw palmetto has also been found to affect the levels of sex hormones such as testosterone and estrogen in other ways.
Much of saw palmetto's popularity as a remedy for hair loss and baldness, however, is based on how it's believed to work rather than on evidence that it actually does. Although there have been some lab studies showing that saw palmetto can inhibit 5-alpha-reductase, there are no well-designed clinical studies showing that saw palmetto can cause hair growth, or stop hair loss or baldness from progressing. One of the only published trials on saw palmetto for baldness is a small study involving 10 men with mild to moderate male pattern baldness. Although promising, the study was too small to provide meaningful evidence.
Like most other herbal supplements, saw palmetto has potential side effects. The most common side effects associated with saw palmetto use are mild stomach pain, constipation, diarrhea, nausea, vomiting, and bad breath. Some men taking saw palmetto have reported erectile dysfunction, breast tenderness or enlargement, and changes in sexual desire.
There have been rare case reports describing liver inflammation, pancreatitis, jaundice, headache, dizziness, insomnia, depression, breathing difficulties, muscle pain, high blood pressure, chest pain, abnormal heart rhythm, blood clots, and heart disease, but it's not clear that these side effects were directly caused by saw palmetto.
Although it hasn't been well-demonstrated in humans, saw palmetto may influence levels of sex hormones such as estrogen and testosterone. Until we know more, people with hormone-sensitive conditions, such as breast cancer, should use caution. Also, saw palmetto could theoretically interfere with oral contraceptives and hormone therapy.
At least two case reports have linked saw palmetto with severe bleeding. People with bleeding disorders or who are taking anticoagulant or antiplatelet medications ("blood-thinners")--such as warfarin (Coumadin), aspirin, or clopidogrel (Plavix)--should avoid taking saw palmetto unless under medical supervision. It should also be avoided at least two weeks before and after surgery.
The safety of saw palmetto for pregnant or nursing women, children, or people with kidney or liver disease hasn't been established.
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