Canada: A study published in JAMA Network Open has concluded that coffee intake increases the risk of kidney dysfunction like albuminuria, hyperfiltration, and hypertension only among slow metabolizers of caffeine in susceptible individuals.
Slow metabolizers of caffeine are 2.7 times more likely to develop albuminuria, 2.5 times more likely to develop hyperfiltration, and 2.8 times more likely to develop hypertension with heavy coffee intake compared with low coffee intake.

Caffeine stimulates CNS and is a psychoactive substance. It exerts adverse effects on kidney function via stimulation involved in glomerular remodelling and sclerosis.
Does coffee consumption confer protection action against kidney diseases?
Does coffee accelerate kidney disease, or is it even associated with kidney disease?
The data in the context mentioned above needs to be more conclusive.
Predominantly caffeine is metabolized by cytochrome P450 1A2 (CYP1A2). This modifies the association between coffee intake and the risk of MI, high blood pressure, and impaired fasting glucose. Those with AC and CC genotypes are slow metabolizers, and those with the AA genotype are fast metabolizers.
Considering this background, researchers assessed whether CYP1A2 genotype rs762551 modified the association between caffeinated coffee intake and markers of kidney dysfunction.
Albuminuria (albumin level of ≥30 mg/24 h) and hyperfiltration (eGFR ≥150 mL/min/1.73 m2) were indicators of kidney dysfunction.
The study points include:
The data was used from HARVEST (Hypertension and Ambulatory Recording Venetia Study).
The study used data from April 1, 1990, to June 30, 2006, with ten years follow-up.
During the first three months, Blood pressure and biochemical data were collected and thereafter repeated every six months.
The study had 1180 untreated participants aged 18-45 years with stage 1 hypertension.
Genotyping, lifestyle questionnaires, and urine analysis data were obtained from 604 individuals, including 438 males aged 33.3 years and a mean body mass index of 25.4
158 participants consumed less than 1 cup of coffee per day
379 participants took 1 to 3 cups per day
Sixty-seven participants had more than 3 cups per day.
Genotype frequencies for rs762551, 43.1% with AA genotype, 40.8% with AC, and 16.1% with CC genotype, did not differ between coffee intake categories.
The risks of albuminuria, hyperfiltration and hypertension with aHR of 2.74, 2.11 and 2.81 increased significantly among slow metabolizers. These individuals consumed more than 3 cups per day.
To conclude, albuminuria, hyperfiltration, and hypertension increase with heavy coffee intake among AC and CC genotypes of CYP1A2 at rs762551 tied to slow caffeine metabolism.
Further reading:
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