In a study from the University of Toronto and elsewhere, scientists found that the association between heavy coffee drinking and kidney disease hinges on a common genetic variation.
They showed that markers of kidney disease were nearly three times higher in heavy coffee drinkers with a variant of the CYP1A2 gene.
The gene variant makes them slow metabolizers of caffeine than other heavy coffee drinkers who had a different version of the gene that enables faster caffeine metabolism.
The team suggests that fast metabolizers can eliminate caffeine from their systems more efficiently and avoid harmful build-ups of caffeine.
Some previous studies have found that caffeine is associated with impaired kidney function and kidney failure, while others have found that coffee may protect against kidney disease.
The amount of caffeine a person consumes also appears to be important.
In the current study, risk of kidney dysfunction was only significant in people who drank three or more cups of coffee a day, which is about 300 mg of Italian espresso.
Current guidelines in Canada and the U.S. recommend no more than 400 mg per day for healthy adults.
The researchers also found that the prevalence of the CYP1A2 gene variant that makes people slow metabolizers of caffeine was similar in both the study group and the general population: roughly 50%.
Many companies and clinics now include CYP1A2 in personalized genetic tests, as different versions of the gene can affect risk for several conditions associated with caffeine consumption.
In the study, the researchers studied three markers of kidney dysfunction: albuminuria (too much of the protein albumin in urine); hyperfiltration (high glomerular filtration rate in the kidney); and high blood pressure.
The team hopes this study will raise awareness about the importance of personalized nutrition recommendations based on individual genetic makeup.
If you care about kidney health, please read studies about how to protect your kidneys from diabetes, and common cholesterol-lowering statin drug may harm kidney health.
For more information about kidney health, please see recent studies about foods that may prevent recurrence of kidney stones, and Stanford finds drug that prevents kidney failure in diabetes.
The study was conducted by Ahmed El-Sohemy et al and published in JAMA Network Open.
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