Rightfully touted for its many health benefits as an antioxidant, green tea doesn’t really play well with iron. A lab study on mice found that consuming an iron-rich diet can greatly reduce the tea’s benefits, as well as the iron’s.

Photo by Wild Bindy.

The main component in green tea is called epigallocatechin gallate (EGCG), a substance still under investigation for its potential to affect human health and disease. EGCG is used in many dietary supplements, but we still don’t know exactly how or why it works. Howeveer, we do know it potently inhibits myeloperoxidase, a pro-inflammatory enzyme released by white blood cells during inflammation. But when EGCG and iron are consumed together, they bind to each other, with EGCG losing its ability to inhibit myeloperoxidase.

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“If you drink green tea after an iron-rich meal, the main compound in the tea will bind to the iron,” said Matam Vijay-Kumar, assistant professor of nutritional sciences, Penn State. “When that occurs, the green tea loses its potential as an antioxidant. In order to get the benefits of green tea, it may be best to not consume it with iron-rich foods.” Iron-rich foods include red meat and dark leafy greens, such as kale and spinach. According to Vijay-Kumar, the same results also apply to iron supplements.

The research can be especially useful for inflammatory bowel syndrome (IBD) patients. EGCG is especially helpful for this condition, as is iron. Dietary supplements containing both substances are often prescribed, which according to the study, is especially counterproductive as it cancels both their effects.

“It is important that IBD patients who take both iron supplements and green tea know how one nutrient affects the other,” Vijay-Kumar said. “The information from the study could be helpful for both people who enjoy green tea and drink it for its general benefits, as well as people who use it specifically to treat illnesses and conditions.”

“The benefit of green tea depends on the bioavailability of its active components,” said Beng San Yeoh, graduate student in immunology and infectious diseases and first author of the study. “It is not only a matter of what we eat, but also when we eat and what else we eat with it.”

It should be noted that the results haven’t been validated for humans.