That’s the same material kidney stones are made of. Doctors found no family history of kidney stones or other issues, according to the Live Science report.

Then the patent mentioned he drank a gallon of black tea every day. Black tea contains a great deal of oxalate, an ingredient found to lead to kidney problems when a large amount is consumed. In this case, they believe the large amount of tea consumed on a daily basis was the likely cause of the kidney failure.

The condition could not be explained by any other cause, according to Dr. Alejandra Mena-Gutierrez.

“With 16 cups of tea daily, the patient’s daily consumption of oxalate was more than 1500 mg,” the report noted. “A level that is higher than the average American intake by a factor of approximately 3 to 10.”

The patient stopped drinking tea, but his kidney failure continues to worsen. It’s not the first time high tea consumption has been noted in health issues.

Live Science cited a 2013 study published in the New England Journal of Medicine, in which researchers described a rare case of bone disease called skeletal fluorosis in a woman who drank a pitcher of tea made from 100 tea bags daily, for 17 years.  In that case fluoride was pointed out as the culprit, a mineral found in drinking water and tea.