An Arkansas man went to the hospital last May complaining of nausea, fatigue, weakness, and body aches. After doctors conducted a kidney biopsy, they realized his kidneys were failing due to a high number of oxalate crystals found in the tissue.

Black tea is a significant source of oxalate, which is naturally found in many foods, and the 56-year-old man admitted to drinking 16 glasses of iced tea a day!

Researchers believe his excessive beverage habit could be the cause of his kidney failure, but can’t prove iced tea was the culprit.

“There are reports about kidney stones related to high oxalate intake attributed to tea, but to our knowledge there are no reports of biopsy-proven nephropathy [kidney damage] associated with excessive consumption of iced tea,” said one of the report’s co-authors, Dr. Alejandra Mena-Gutierrez, of the University of Arkansas for Medical Sciences in Little Rock.

Although it can’t be proven that iced tea led to this man’s condition, doctors often put kidney stone patients on low-oxalate diets. Beverages that are considered high-oxalate drinks include black tea, dark beer, instant coffee, and Ovaltine.

Unfortunately, the man needed dialysis, and remained on it because the damage to his kidneys was so severe.

Researchers reported the man’s case in the April 1 New England Journal of Medicine.