Drinking more than three cups of caffeinated coffee a day is associated with less liver stiffness, according to an analysis of a nationally representative survey, which was recently published in Clinical Gastroenterology and Hepatology.
The study is likely the most rigorous look to date on the benefits of coffee on liver health in the U.S. It was based on data from the National Health and Nutrition Examination Survey (NHANES), in which participants were asked about what they eat and drink. Crucially, in 2017, NHANES began to include elastography (FibroScan), of participants’ liver stiffness, not because of suspected problems with the liver but as across-the-board evaluations of all participants.
Dr Elliot Tapper “Because it’s an unselected population for FibroScan and because of the detail, the granularity, the richness of the information from the nutritional surveys that they do, this is the closest we’re ever going to get to a linkage between what people are eating or drinking and the health of their liver, absent a longitudinal study where we set out to follow people for many, many years,” said Elliot Tapper, MD, assistant professor of gastroenterology at the University of Michigan, Ann Arbor, and the study’s senior author.
Researchers examined data from about 4,500 patients who had participated in the NHANES study in 2017-2018. The participants were aged 20 years or older, with an average age of 48; 73% were overweight, about the national average.
The researchers found no association between coffee consumption and controlled attenuation parameter (CAP), a measure of fatty liver. But they found a link between coffee and liver stiffness.
Those who drank more than three cups of coffee daily had a liver stiffness measure (LSM) that was 0.9 kilopascals (kPa) lower than others (P = .03). Drinking more than three cups a day also was found to be protective against an LSM of 9.5 kPa or higher, the threshold for advanced liver fibrosis (OR, 0.4; P = .05).
Decaffeinated coffee was not found to be associated with LSM.
Caffeine is an antagonist to adenosine receptors in the liver cell that, if blocked, stops the production of scar tissue, according to the researchers. But when they looked at estimated caffeine consumption, calculated through the detailed, trained interviews performed by nutritionists, there was no association with liver stiffness. That said, Tapper noted that this could be due to the imperfection of making those estimations.