Millions of middle-aged men take saw palmetto extract to relieve the urinary-tract symptoms of an enlarged prostate, but a new study finds that the supplements work no better than placebo.
The findings follow about a decade of accumulating evidence that the popular herbal remedy has questionable benefit for common problems related to prostate growth. Nearly all men experience prostate enlargement — known as benign prostatic hyperplasia, or BPH — as they age. Most have mild symptoms or none at all, but when an enlarged prostate impinges on the urethra, it can cause urinary and bladder problems, including difficulty urinating, weak or intermittent urine flow and frequent urges to go to the bathroom, especially at night. For many men, the symptoms interfere with quality of life.
There are drugs to treat the problem, but they have side effects. So, doctors sometimes suggest trying saw palmetto, which has been thought to help because of its anti-androgenic and anti-inflammatory properties. But in a series of studies, the plant extract has fallen short. The largest previous trial to date, enrolling 225 men over age 49, found that saw palmetto was no more effective than a dummy pill. That study was published in the New England Journal of Medicine in 2006.
The new trial went bigger, with 369 men aged 45 or older. It also bettered the dosage: the 2006 trial used 320 mg of the plant extract daily, the standard recommended dose; the new trial started men out at 320 mg, doubled it at six months, then tripled it to 960 mg daily after a year. The men were randomized to take either saw palmetto or a placebo every day for a total of 18 months.
Both groups saw “slight” improvement in their symptoms, but men taking saw palmetto were no better off than those who got placebo. At the start of the study, participants had moderate urinary symptoms of BPH, registering an average score of 14.6 on a 35-point scale of symptom severity. By the end of the trial, that score had dropped two points in men taking saw palmetto, and three points in those taking placebo.
But here’s the thing: the men actually did show slight relief of symptoms, and for about 40% to 45% of them, it made a noticeable difference in their everyday lives, the authors said. Granted, the improvement was due to the placebo effect, but given that saw palmetto didn’t have any side effects, not even at the highest doses, the researchers aren’t quite ready to give up on it yet. (The study was funded by grants from the National Institutes of Health.)
Many men who take saw palmetto say it helps. So, aside from the cost of the supplement, there isn’t much other measurable harm. “While I would tell a patient interested in trying saw palmetto that I wouldn’t object, I’d make sure he understood that, on average, it doesn’t seem to work any better than a placebo,” said lead author Dr. Michael Barry of Massachusetts General Hospital’s department of medicine.
The new study was published in the Journal of the American Medical Association.