Heavy Coffee Consumption Increases Prediabetes Risk Among Hypertensive Patients

The risk for developing prediabetes was doubled among hypertensive patients who drank more than 3 cups of coffee per day.

Drinking coffee may increase the risk for prediabetes among hypertensive adults, especially those who metabolize caffeine slowly and are overweight or obese.

In the Hypertension and Ambulatory Recording VEnetia Study (HARVEST) trial presented at the 2014 European Society of Cardiology Congress in Barcelona, Spain, the effect of coffee consumption on glucose metabolism was analyzed in a group of patients diagnosed with stage 1 hypertension. The trial included a total of 1180 patients aged 18 to 45 years, 639 of whom underwent genotyping for CYP1A2, the enzyme that metabolizes caffeine.

Overall, 74% of the patients drank coffee. Among them, 87% drank a moderate 1 to 3 cups of coffee each day, while 13% were considered heavy drinkers, consuming more than 3 cups each day.

After a median follow-up of 6.1 years, 24% of the patients were diagnosed with prediabetes. Compared to those who did not drink coffee, moderate coffee consumers had a 34% increased risk for developing prediabetes, while heavy drinkers had twice the risk. Analyzed by body mass index, the association between coffee and increased prediabetes risk remained significant among overweight and obese patients, but it lost significance among those with normal weights.

The HARVEST trial also found the effects of coffee consumption differed based on CYP1A2 genotyping, as it was associated with prediabetes risk only among slow caffeine metabolizers, but it did not have a significant effect on fast caffeine metabolizers.

“Slow caffeine metabolisers are exposed for a longer time to the detrimental effects of caffeine on glucose metabolism,” lead study author Lucio Mos stated in a press release. “Thus, the effect of coffee on prediabetes depends on 2 factors: the amount of daily coffee intake and the individual’s genetic background.”

The findings contradicted previous studies that suggested coffee consumption lowers the risk of developing type 2 diabetes.

“Young-to-middle-age people with hypertension should be aware that coffee consumption may increase their risk of developing diabetes in later life,” said Mos. “Genotyping for the CYP1A2 gene polymorphism could help them to better know their risk. (Those) who are slow caffeine metabolisers should abstain from drinking caffeinated coffee.”