How much of a good thing is too much? In this case, 16 cups per day.
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.