Men with enlarged prostates who took higher doses of the herbal supplement saw palmetto had no greater relief from incontinence or difficult urination than those given a placebo, researchers said. More than 300 men at least 45 years old were given a daily dose of saw palmetto or a sugar pill. Over 17 months, those on the supplement had their doses increased to 960 milligrams, or triple the standard amount, according to the study released today in the Journal of the American Medical Association.