Dear Dr. SerVaas: A friend of mine heard that the use of saw palmetto forever skews the results of PSA tests. Would you please address this issue?

Jack Garton
Cheyenne, Wyoming

Dear Reader: You bring up an important point. Herbs and other supplements can sometimes interfere with diagnostic tests. In this case, however, Indianapolis urologist Dr. Phillip Mosbaugh says that saw palmetto does not seem to alter the results of PSA (prostate-specific antigen) blood tests for prostate cancer. Dr. Mosbaugh explains:

"Saw palmetto does not appear to have any effect on total- or free-PSA levels in studies where this has been monitored. The herb does have anti-androgen effects. Although most trials have been done in Europe and not well monitored or standardized, taking saw palmetto has been shown to improve urinary flow rates and reduce symptom scores.

"The quality of saw palmetto depends on the purity of the Serenoa Repens fruit extract. There are currently over 30 brands available in the United States. The National Institutes of Health have authorized studies exploring various phytotherapies, including saw palmetto. For now, however, one should not be concerned about PSA levels while taking saw palmetto."