Q: What is erectile dysfunction, and are there any natural medicines that can treat it?

A: Erectile dysfunction is a condition in which men are unable to achieve or maintain an erection sufficient for satisfactory sexual function. It can affect personal relationships, self-esteem and quality of life.

A common disorder in the United States, it affects approximately 50 percent of men ages 40 to 70. Some men with ED have impaired blood flow to the penis, which can be caused by a variety of factors; the most common are heart disease, diabetes, hypertension and smoking. ED can also be the result of using pharmaceutical medications that alleviate depression.

There are a number of natural medicines that can help treat it. Among those most substantiated by research are panax ginseng, L-arginine, Pycnogenol and ginkgo biloba.

Panax ginseng, also known as Korean ginseng, has been used for thousands of years in Asia to enhance sexual potency. Recent research has found that it can have a beneficial effect on ED because of its antioxidant effects and its ability to increase nitric oxide, which improves penile blood flow. A study published in the Asian Journal of Andrology in 2007 found a significant improvement in erectile function in men treated with panax ginseng. The study also noted that there were no changes in blood levels of testosterone — an important consideration for men with a history of either prostate cancer or benign prostatic hypertrophy. The dose of panax ginseng used in the study was 1,000 milligrams three times daily.

L-arginine is an amino acid that can benefit those suffering from ED because it is the precursor to nitric oxide, which is involved in dilating blood vessels. One study, published in the Journal of Sex and Marital Therapy in 2003, showed that L-arginine in combination with Pycnogenol — a flavonoid from pine bark that has an effect on nitric oxide — had significant benefits in normalizing erections in 92.5 percent of the participants. The doses used in the study were 1.7 grams of L-arginine and 80 milligrams of Pycnogenol daily.

Ginkgo biloba, a herb used for enhancing memory, may also help alleviate ED in those taking antidepressant medications.

According to Alternative Medicine Review in 2004, "an open trial of ginkgo to alleviate antidepressant-induced sexual dysfunction found ginkgo to be 76 percent effective in alleviating symptoms related to all phases of the sexual response cycle in men, including erectile dysfunction."

The average dose prescribed in the trial was 207 milligrams daily.

Laurie Steelsmith is a naturopathic physician and licensed acupuncturist in Honolulu, as well as author of the book "Natural Choices for Women's Health" (Random House). Reach her and read her past columns at www.DrSteelsmith.com. This column is for information only. Consult your health provider for medical advice.