NEW YORK — Hypericin, the active ingredient in the popular herbal anti-depressant St. John’s Wort, can damage the eye significantly if the eye is exposed to intense bright light, according to research presented by chemistry Professor Joan Roberts at the annual meeting of the American Society of Photobiology in July.
Roberts’ study of St. John’s Wort, which is available without a prescription, reveals that it is phototoxic. If it is ingested and the hypericin travels to the eye, and that person is then exposed to visible or ultraviolet bright light, the hypericin can induce changes in lens protein that could lead to the formation of cataracts, she said. Roberts, who studies ocular phototoxicity at both Fordham and the National Institute of Environmental Health Sciences (NIEHS), has been conducting her research with two Fordham students, Michael Datillo and R.H. Wang, and Colin Chignell at the NIEHS. They have been researching which ingestible products — including drugs, herbs and food — can cause damage to the eye when exposed to light. Roberts’ findings are particularly alarming since millions of people take this natural remedy in combination with some form of light exposure as treatment for a form of depression called Seasonal Affective Disorder, which usually strikes during the winter, when there are fewer hours of daylight. Compounding the risk is the fact that cataracts take five to 10 years to develop and during that period are symptomless. People at risk for developing cataracts may not know to choose alternate therapies to beat the winter blues. “I support effective alternative medicines,” Roberts said.
“However, in this case, I would either take St. John’s Wort or choose exposure to the sun [as treatment]. Certainly, people who take this herb should not simultaneously use light-box therapy or spend any time out in the sun whether walking, sunbathing, bike riding, swimming, skiing or performing any other outdoor activity.” Other experts in the field agree there is a correlation between the herb and bright light. Ivor Roots, a clinical pharmacologist at Humboldt University in Berlin, told New Scientist magazine in an article about Roberts’ research that in Germany it is “recommended to avoid tanning beds while taking St. Johns Wort.” Roberts’ next step is to conduct clinical studies with people who take St. John’s Wort regularly so she can determine accurately the frequency of cases where hypericin is present in their eyes. Determining the presence of hypericin is relatively easy to do since it is fluorescent and easily identifiable when looking at an eye using a method called ocular fluorometry, Roberts said.
As often is the case with science, the results of one study can serendipitously help other research efforts, and the St. John’s Wort/sun combination actually is shedding light on a potential cancer treatment. According to Roberts, scientists are studying the merits of photodynamic therapy (PDT), whereby light or laser stimulation enables an otherwise ineffective drug to kill cancerous cells. “PDT treatment methods are most effective for skin cancer, however, the method is very dangerous when used to treat eye- or brain-related cancers,” Roberts said. There’s a chance that the compound would leak and damage healthy cells and cancer-free areas when used to treat eye or brain cancers, she said. Roberts currently is testing her own method of PDT that kills forms of eye cancer without harming cancer-free areas.
