How Much Coffee Can Harm Your Kidneys

A study of 1,180 adults with stage 1 hypertension found that drinking three or more cups of coffee a day may harm the kidneys. In people with slow caffeine metabolism (CYP1A2 gene variant), the risk of kidney dysfunction increases 2.7-fold. Doctors advise limiting coffee and controlling blood pressure.

New research shows that drinking three or more cups of coffee a day can harm the kidneys, especially in people with stage 1 hypertension. The study involved 1,180 adults aged 18 to 45 with elevated blood pressure. Scientists monitored signs of kidney dysfunction and focused on the CYP1A2 gene, which is responsible for caffeine metabolism. About half of the participants had a variant of this gene that slows caffeine breakdown. Among those who metabolize caffeine more slowly, the risk of kidney dysfunction increased 2.7-fold with daily consumption of three or more cups of coffee. Slower metabolism leads to longer caffeine exposure, increasing stress on the kidneys, raising blood pressure, and causing fluid retention. Doctors recommend that people with hypertension limit coffee intake, control blood pressure, and regularly check kidney function.