Several popular over-the-counter herbs, including St. John's Wort and echinacea, could badly affect people's fertility. High doses of echinacea, ginkgo and St. John's wort can damage reproductive cells, can stop sperm from fertilizing eggs and might damage eggs and sperm.

St. John's Wort is sold widely for use in treating depression and anxiety, and has been shown in clinical tests to help, while gingko biloba is marketed for boosting memory and can help Alzheimer's patients. Echinacea is sold to boost the immune system to fight off colds and flu.

The researchers did not test people taking the herbal preparations but instead worked in the laboratory. They took hamster eggs, removed the zona pellucida or outer shell-like coating, exposed them to the herbs and then mixed in human sperm. Healthy human sperm usually can penetrate the egg, but will not fertilize it. At very low concentrations there was no effect, but at higher doses St. John's Wort prevented the sperm from penetrating the eggs. Echinacea and gingko impaired penetration, and palmetto, sold to help prostate problems, had no measurable effect.

Fertility and Sterility March 1999

COMMENT: This is a great example of a study that you might see in the paper and wonder, gee maybe this natural medicine is not all it’s cracked up to be. But if you carefully examine the details, you will find that this is a laboratory study NOT a human study. There is no demonstration that these herbs reach the concentration in their non-metabolized form on the eggs and sperm after they are swallowed by real live human beings. I am not a great fan of herbs. I view them as a safer alternative to drugs, but one still must be careful with them. However, I am not concerned about this study until the researchers are able to perform their measurements under more realistic circumstances.