In May 2014, a 56-year-old man arrived in the emergency department at the veterans' hospital in Little Rock, Arkansas. He reported intense but vague symptoms: weakness, fatigue, and body aches. The emergency-room team drew some of his blood and found it bursting with a waste chemical called creatinine—more than four times the normal level. That meant he was experiencing severe kidney failure. Doctors started urgent dialysis, cycling the blood out of the man's body, through a machine that cleaned it in lieu of functional kidneys.
The University of Arkansas physicians who managed the case were perplexed, they report in the current issue of The New England Journal of Medicine. What causes an otherwise healthy person to develop such dramatic renal failure? Another clue initially confused the picture: Urine tests found oxalate crystals at more than twice the upper limit of normal. When they show up in those quantities, doctors are taught to ask if the person has been drinking antifreeze, because ethylene glycol can cause oxalate crystals to accumulate. This man denied drinking antifreeze—as people who drink antifreeze tend to do. But the doctors didn't need to pursue that line because, they report, "on further questioning, the patient admitted to drinking 16 eight-ounce glasses of iced tea daily." And then it made sense.
The man had been brewing the tea at home, and luckily, despite the Southern tradition, it was unsweetened. Black tea constitutes upwards of 80 percent of the tea consumed in the United States, and it is high in oxalate, a chemical that is a metabolic byproduct in many plants. If a person is eating a lot of those plants, regardless of said person's relationship to antifreeze, oxalate can build up in the kidneys and lead to renal failure. In this case, the doctors did a biopsy of the man's kidneys and found oxalate throughout the renal tissue.