Even when it comes to delicious, refreshing drinks, too much of a good thing can sometimes be dangerous: In a letter published in a scientific journal, doctors say drinking a gallon of iced tea every day could’ve led to kidney failure in a 56-year-old man who just couldn’t get enough of the stuff.

The New England Journal of Medicine calls it iced-tea nephropathy in a new letter describing the case, reports Reuters Health, warning others that massive consumption of tea could be responsible for other unexplained cases of kidney failure.

The 56-year-old man suddenly developed weakness, fatigue and body aches, and it seems the source of his ailments was an excessive amount of oxalate, which is a compound found in many foods. You can also get a build-up of oxalates from “juicing” too much, gastric bypass surgery, and eating foods chock full of ascorbic acid like beets, spinach, nuts and strawberries.

Before you swear off any of those foods however, rest assured that the amount you’d have to consume is a heck of a lot — the man said he drank 16 nine-ounce glasses of iced tea a day, resulting in an intake of more than 1,500 milligrams of oxalate per day. That’s well above the advised 40-50 mg limit per day, according to the Academy of Nutrition and Diatetics recommendations.

“If you drink tea once or twice a day, it probably wouldn’t exceed what is the normal range for Americans. But this patient was taking 10 times that amount,” said Dr. Umbar Ghaffa of the University of Arkansas for Medical Sciences in Little Rock, a coauthor of the letter.

Too much oxalate can lead to kidney stones, which in turn can damage the kidney by blocking the flow of urine. Ghaffar told Reuters that this case involved oxalate crystals actually inside the kidney, which generates an inflammatory reaction.

“If that’s not resolved it will cause scarring and loss of the kidney tissue. So that’s what probably was happening in this patient,” he explains.

On the other hand, previous research has shown that people who drink tea in normal amounts can have a lower risk of kidney stones, another professor who was not involved in this case told Reuters.

“But in this case, the person was drinking huge amounts of oxalate,” said Dr. Gary Curhan, a professor of medicine at Harvard Medical School. “I would caution people against drinking that much, but drinking a glass or two would not concern me.”

Massive tea consumption linked to kidney failure [Reuters Health]

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