Coffee Wikipedia image

Coffee May Raise Risk of Kidney Disease and Hypertension in About Half of Population Interview with:

Dr. Sara Mahdavi

Dr. Mahdavi

Dr. Sara Mahdavi, PhD
Clinical Scientist and Clinical Instructor
Research Appointment in the Faculty of Medicine
University of Toronto
Toronto, ON What is the background for this study?

Response: This was a long-term study spanning 16 years and began with a population of young adults who were medically assessed on a regular basis. It was remarkable to see just how striking the effects of coffee were in the group that had the susceptible genetic variant, what we termed “slow caffeine metabolizers” yet no effect whatsoever in those who did not were termed “fast metabolizers”. What are the main findings?

Response:  Slow metabolizers who drank more than 3 cups of coffee per day were 2.7 times more likely to develop kidney dysfunction and 2.8 times more likely to develop hypertension. Since slow metabolizers represent roughly half of the population, this is an important factor to take into consideration for those who consume 3 or more cups of coffee per day. This is a very important discovery firstly because about 50% of a population are slow metabolizers, and we already have seen negative health outcomes for this group in terms of increased risk of heart attacks and hypertension, so this is just more reason to consider reducing caffeine intake, whether it be reducing coffee intake to less than 300mg per day or switching to decaffeinated coffee instead. Is DNA testing for this variant commonly available?

Response:  There are now several genetic testing companies that test for this CYP1A2 variant, and testing is readily available to consumers, by providing a saliva sample but the interpretation of genetic testing data usually requires a health care professional who can review the results with an individual. Personally, I use Nutrigenomix Inc because they are the largest provider of genetic testing for personalized nutrition for healthcare professionals and I am confident about their science as I, along with several other scientists, serve on their international science advisory board. What should readers take away from your report?

Response: Since slow metabolizers represent roughly half of the population, we need to revisit current guidelines that permit up to 4 cups per day for everyone. Our research also adds further evidence for the use of genetic testing for personalized nutrition rather than one-size-fits all. This type of tailored approach to health care and preventative medicine is the way of the future and what many cutting edge clinics already use worldwide. What recommendations do you have for future research as a results of this study?

Response: It would be interesting to conduct an intervention trial where we take a group of slow metabolizers who drink more than 3 cups of coffee per day and randomize them to either continue their coffee drinking habit or to switch to decaf and see if we can slow the progression of kidney dysfunction. Is there anything else you would like to add? Any disclosures?

Response: These latest findings add to the growing body of evidence that suggests the current guidelines for coffee consumption may be harmful for half the population. They also shed light on the benefits of genetic testing for personalized nutrition.

Disclosures: Dr. Mahdavi serves on the Science Advisory Board of Nutrigenomix Inc.


Mahdavi S, Palatini P, El-Sohemy A. CYP1A2 Genetic Variation, Coffee Intake, and Kidney Dysfunction. JAMA Netw Open. 2023;6(1):e2247868. doi:10.1001/jamanetworkopen.2022.47868

The information on is provided for educational purposes only, and is in no way intended to diagnose, cure, or treat any medical or other condition. Always seek the advice of your physician or other qualified health and ask your doctor any questions you may have regarding a medical condition. In addition to all other limitations and disclaimers in this agreement, service provider and its third party providers disclaim any liability or loss in connection with the content provided on this website.



Last Updated on March 1, 2023 by Marie Benz