After a 56-year-old man experienced kidney failure, his doctors discovered that his habit of drinking excessive amounts of iced tea every day was likely the culprit, according to a new report of his case.
The man's kidney function has not recovered, and he remains on dialysis, said Dr. Alejandra Mena-Gutierrez, of University of Arkansas for Medical Sciences, who treated the patient and wrote the report of his case. The authors of the report stressed that moderation is key when it comes to drinking tea.
"We are not advising against tea consumption," Mena-Gutierrez said. "If you are healthy and drink tea with moderation, it should not cause damage to your kidneys."
In May 2014, the man was admitted to an Arkansas hospital, feeling weak and achy. Tests showed that his urine had high levels of calcium oxalate crystals, which are the components of kidney stones.
But the man had no family history of kidney disease, nor had he previously had kidney stones, according to the report. To treat his kidney failure, the doctors began dialysis. [7 Foods You Can Overdose On]
The man told his doctors that he drank 16 glasses of iced tea daily. Black tea — which was in the iced tea the man drank — is a rich source of oxalate, a compound that may contribute to kidney problems if consumed in high quantities.
The doctors concluded that the man's excessive consumption of oxalate in the iced tea likely led to the kidney failure that was progressing rapidly.
The man'scondition "could not be explained by any other cause in this case," Mena-Gutierrez told Live Science.
The average person in the United States consumes between 152 to 511 milligrams of oxalate a day, according to the report. This is higher than the 40 to 50 mg per day recommended by the Academy of Nutrition and Dietetics.
There are between 50 and 100 mg of oxalate per 100 ml of black tea, the researchers wrote in the report.
"With 16 cups of tea daily, the patient's daily consumption of oxalate was more than 1500 mg — a level that is higher than the average American intake by a factor of approximately 3 to 10," they wrote.
In another report, published in 2013 in the New England Journal of Medicine, 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 the woman's case, her bone disease was likely caused by consuming too much fluoride, a mineral that is found in tea and drinking water, according to that report.
The new report was published today (April 1) in the New England Journal of Medicine.
Sign up for the Live Science daily newsletter now
Get the world’s most fascinating discoveries delivered straight to your inbox.