A recent study from the University of Toronto has found that drinking a lot of coffee might affect kidney health differently depending on a person’s genes.
The research focused on a gene called CYP1A2, which determines how fast the body breaks down caffeine.
To understand this, imagine two coffee lovers, Alice and Bob. Both drink several cups of coffee every day, but their bodies process caffeine differently.
Alice is a slow metabolizer, meaning her body takes longer to break down caffeine. Bob, on the other hand, is a fast metabolizer, clearing caffeine quickly.
The study found that people like Alice—who process caffeine slowly—are at a much higher risk of kidney problems if they drink a lot of coffee. Their risk was nearly three times higher compared to fast metabolizers like Bob.
Scientists have long debated whether coffee is good or bad for kidney health. Some studies suggest caffeine might be harmful, potentially leading to kidney damage.
Others have found benefits, such as lower risks of certain diseases. This new study adds another piece to the puzzle: it’s not just about coffee itself, but also about how each person’s body processes caffeine.
Researchers looked at key indicators of kidney function, including:
- Protein in urine (albuminuria) – a sign of kidney stress
- Filtration rate (hyperfiltration) – how hard the kidneys are working
- Blood pressure – which can affect kidney health over time
They found that heavy coffee drinkers who metabolize caffeine slowly showed more signs of kidney problems. The risk increased when coffee intake was more than three cups per day (about 300 mg of caffeine)—close to the daily limit recommended in many countries like Canada and the U.S. (400 mg).
Why Does This Happen?
Caffeine affects blood pressure, blood flow, and kidney function. In slow metabolizers, caffeine stays in the body longer, meaning its effects last longer too. This may put extra strain on the kidneys over time. Fast metabolizers, however, clear caffeine quickly, which may protect them from these negative effects.
About half of the population has the slow metabolizer gene, meaning many coffee drinkers could unknowingly be at risk.
Not necessarily. The study doesn’t say that coffee is bad for everyone. Instead, it suggests that some people need to be more cautious about their caffeine intake based on their genetics.
More companies and clinics now offer genetic testing for CYP1A2 to help people understand how their bodies process caffeine. This can lead to personalized nutrition plans, where diet recommendations are based on an individual’s unique genetic makeup.
This research, led by Dr. Ahmed El-Sohemy and published in JAMA Network Open, highlights the growing field of personalized health care. Instead of general diet rules, future health advice may be tailored to each person’s genetics.
For coffee lovers, this means that knowing your genetic profile could help you make smarter choices about your daily caffeine intake—protecting your kidney health while still enjoying your favorite drink.
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