Medical Edge Newspaper Column

Possible Connection Between Hypericin and Eye Damage

January 28, 2008
Dear Mayo Clinic:
I've read that hypericin, the ingredient in St. John's wort, is damaging to the eye lens and perhaps the cornea. I take one or two 300-milligram tablets a day with a minimum of 0.3 percent hypericin. My ophthalmologist says lab studies don't always translate to real life. Is this herb safe? Am I damaging my eyes?

Answer:
A few recent studies are looking at connections between hypericin, the active ingredient in the herbal supplement St. John's wort, and possible eye damage.

Researchers are questioning whether hypericin increases sensitivity to ultraviolet rays from the sun. The research is in the very early stages and involves laboratory studies, not clinical trials with patients. Results indicate there is some reason for caution, but the real risk is unknown.

Until more is known, it's best to use common-sense precautions in the sun when you are taking St. John's wort. Wear sunglasses. Put on a hat. For everyone, ultraviolet exposure is a risk factor for cataracts and macular degeneration, a progressive eye disease that causes loss of central vision in one or both eyes.

Depression is the most common reason people elect to take St. John's wort. Studies have shown it to be helpful for people with mild to moderate depression. Some use it for other conditions, including seasonal affective disorder, premenstrual syndrome, and perimenopausal symptoms.

Like all herbs and supplements, St. John's wort is subject to limited regulatory oversight by the U.S. Food and Drug Administration (FDA), which means the product isn't put through the rigorous review process that new drugs must undergo before being "approved." In addition to concerns about increased sensitivity to sunlight, St. John's wort is known to interact with a number of prescription medications, including warfarin, oral contraceptives, and seizure and HIV medications. I would advise you to discuss the risks and benefits of this supplement with your primary care doctor or health care team.

— Brent Bauer, M.D., Complementary and Integrative Medicine Program, Mayo Clinic, Rochester, Minn.