Is drinking coffee/caffeine bad for your kidneys?

Ever since coffee was discovered over a millennium ago in Ethiopia, pages upon pages have been written about the myriad health effects of caffeine. Being a psychoactive substance, caffeine has been regulated and even banned for multiple reasons ranging from the religious, to its effect on “overstimulating the senses”. Books have been written about even the “sexual hysteria” it could cause! 

But lets talk about it from an objective, health perspective. I am going to restrict myself to the cardiovascular and renal effects of coffee (the effects of coffee are dose dependent; please note that a single, 8 oz cup of coffee has about 100-200 mg of caffeine). 

CARDIOVASCULAR EFFECTS, BLOOD PRESSURE, AND KIDNEY DISEASE

There is some evidence that caffeine can cause momentary increases in the blood pressure (up to 10 mm Hg), especially in people who are not habitual coffee drinkers. However, this effect is enhanced in the elderly, and people who have underlying hypertension. Beyond this short lived spike in blood pressure, there is some data that caffeine could have a long term chronic effect on raising the blood pressure as well.

Given hypertension’s deleterious effects on the kidneys’, it would seem plausible that moderating caffeine intake could indirectly have a beneficial effect on the kidneys. However, despite the possibility of these kidney damaging effects of caffeine that would “make sense”, the evidence has not quite panned out that way. And so, if we look at the aggregate data available at this time, it would appear that consuming the equivalent of 3-4 cups of coffee daily does not increase the risk of kidney disease. This applies to the average person. There still are special situations like kids and the elderly where caution needs to be taken given the other cardiovascular and diuretic effects. A similar rider might also apply to people who are at risk of forming kidney stones. 

My take home message: if you don’t fit any of the special categories mentioned above, it is probably safe to consume moderate amounts of coffee from a kidney standpoint! 

Veeraish Chauhan, MD, FACP, FASN

Nephrology

Bradenton / Sarasota, FL