A puzzling medical case in which a 56-year-old man suddenly developed weakness, fatigue, and body aches, was, upon further investigation, revealed to be linked to the patient’s daily consumption of sixteen 8-ounce glasses of iced tea.

Photo Credit: Peter Moore | CC BY-NC-SA 2.0

The man’s doctors describe his case in Thursday’s issue of the New England Journal of Medicine (emphasis added):

A 56-year-old man presented to the hospital in May 2014 with weakness, fatigue, body aches, and an elevated serum creatinine level (4.5 mg per deciliter [400 μmol per liter]). Review of his medical record indicated previous creatinine levels of 1.2 mg per deciliter (110 μmol per liter) in October 2013 and 2.5 mg per deciliter (220 μmol per liter) in February 2014. He had no proteinuria or hematuria. The urine sediment was remarkable for the presence of abundant calcium oxalate crystals. He did not have a personal history of kidney stones or any family history of kidney disease. He reported not consuming ethylene glycol. He had no malabsorptive symptoms or history of gastric surgery. On further questioning, the patient admitted to drinking sixteen 8-oz glasses of iced tea daily. Worsening renal failure with uremic symptoms necessitated the initiation of dialysis.

Results from a urine analysis hinted at a diagnosis that a kidney biopsy would later corroborate: the problem was down to an excess of oxalate, a compound found in a range of edible plants – like star fruit, spinach, beets and tea leaves – that is particularly infamous for leading to kidney stones when consumed in excess. (It’s also a metabolic byproduct of ethylene glycol, better known as antifreeze. Its sweet taste means that ethylene glycol is occasionally ingested accidentally, which is why the additive gets a mention in the diagnostic procedure recounted above).

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Because oxalate is so ubiquitous, most people consume a fair bit of it on a daily basis – in the range of 152 and 511 mg per day, according to urology and nephrology studies cited by the authors. That’s greater than the maximum daily intake recommended by the Academy of Nutrition and Dietetics (less than 40–50 mg/day), but it’s still nowhere near the estimated daily intake of the tea-lover documented in the NEJM, whose daily consumption of oxalate, the authors estimate, was in excess of 1,500 mg – “a level that is higher than the average American intake by a factor of approximately 3 to 10.”

The man’s doctors are calling it “iced-tea nephropathy.” We’re calling it a warning to immoderate tea drinkers everywhere.

[ NEJM]