Drinking green tea confers many health benefits, particularly due to the powerful polyphenols contained within, which have antioxidant effects greater than those of vitamin C. But a new study suggests that consuming iron alongside green tea blocks the health benefits of the tea, especially in the wake of inflammatory bowel disease.
The study, led by Matam Vijay-Kumar of Penn State, is published in the American Journal of Pathology.
In the study, the researchers note that the green tea-derived polyphenol epigallocatechin-3-gallate (EGCG) has been widely studied for its antioxidant and anti-inflammatory characteristics in inflammatory bowel disease (IBD) models, but the underlying mechanism is not entirely understood.
The polyphenols present in teas are catechins, a type of natural antioxidant. Although green tea has six primary catechin compounds, EGCG is the most studied and the most active.
However, Beng San Yeoh, first author of the latest study and graduate student at Penn State, notes that the "benefit of green tea depends on the bioavailability of its active compounds. It is not only a matter of what we eat, but also when we eat and what else we eat with it."
'Main compound in green tea binds to iron'
In their study, the researchers say that EGCG inhibits myeloperoxidase, which is a pro-inflammatory enzyme that is released by white blood cells in the wake of inflammation. As such, when EGCG inactivates myeloperoxidase, it could help to curb IBD flare-ups.
As such, IBD patients are often prescribed iron supplements.
However, the researchers found that when EGCG and iron are consumed at the same time, the EGCG loses its power to inactivate myeloperoxidase.
"If you drink green tea after an iron-rich meal," says Vijay-Kumar, "the main compound in the tea will bind to the iron. When that occurs, the green tea loses its potential as an antioxidant."
He adds that, to get the benefits of green tea, "it may be best to not consume it with iron-rich foods." Foods that are high in iron include red meat and dark, leafy greens, including kale and spinach.
Furthermore, if patients with IBD are prescribed iron supplements, drinking green tea at the same time would be counterproductive; EGCG and iron would bind together, cancelling each other out.
Vijay-Kumar concludes the study by noting:
"It is important that IBD patients who take both iron supplements and green tea know how one nutrient affects the other. 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."
Medical News Today previously reported on a study that suggested too much green tea could be harmful to reproductive function and development.