Does she drink tea?

I was quickly moving along through my busy university clinic, seeing another CKD patient when the nurse came to inform me that the patient’s hemoglobin was critically low at 5 g/dl, while the patient appeared to be just fine. I reviewed the rest of labs just to find out that the iron studies were even more impressive: iron saturation 3% and ferritin 2 ng/ml.

I inquired about the usual suspects - bleeding from various sources - but no luck there (the patient was post-menopausal and denied GI bleeding, later ruled out by EGD and colonoscopy)... Failing to identify a cause of her iron deficiency, I presented the case to my staff who, after reviewing the data, asked me an unusual question: does she drink tea? To my surprise, indeed, the patient admitted to drinking large quantities of black tea. Still puzzled about the link between the two, I jumped onto Google Scholar.

In the renal world, the only time when we talk about tea is when discussing hyponatremia in patients that are on a “tea and toast” diet. So what did I find out? An interesting South African study demonstrated that black tea inhibits non-heme iron absorption by forming iron tannate complexes. This was confirmed by a UK study which showed that black tea was the most potent out of all polyphenol-rich beverages (coffee, cocoa, etc.) in inhibiting absorption of non-heme iron.

Iron deficiency anemia is common in CKD patients, one of the latest mechanisms to be described involves the hepcidin-ferroportin axis (as recently reviewed in JASN). But today I discovered another one!

Posted by Tomoki Tsukahara