Increased intake of both regular and decaffeinated coffee was significantly associated with a reduced severity of NAFLD in the study, published in Nutrients. The study participants included 156 overweight adults, most of whom had type 2 diabetes.
A confluence of factors including diet and lifestyle changes and increased obesity have contributed to a rise in type 2 diabetes and of NAFLD, Margarida Coelho, of the Center for Neuroscience and Cell Biology at the University of Coimbra (Portugal), and colleagues wrote.
Previous studies support an association between coffee and protection against NAFLD, but the roles of the caffeine and noncaffeine components of coffee have not been examined, corresponding author John Griffith Jones, PhD, also of the Center for Neuroscience and Cell Biology at the University of Coimbra, said in an interview.
“There have been previous studies indicating a link between coffee intake and NAFLD amelioration, but these were entirely based on self-reporting questionnaire data, but the main limitation of this approach is that it does not provide any information on which components of coffee confer the beneficial effects,” Dr. Jones said. “The development of new analytical techniques allowing reliable profiling of coffee metabolites in urine allowed this limitation to be addressed.”
Dr. Jones and associates examined the relationship between consumption of regular and decaffeinated coffee on the fatty liver index (FLI), a validated predictor of NAFLD. They measured coffee intake of 156 overweight adults, 135 of whom had type 2 diabetes. The study population included 76 women and 80 men with a mean age of 59 years and a mean body mass index of 29 kg/m2.
The participants reported coffee intake via questionnaires, and 98 participants (all with type 2 diabetes) also provided urine samples for measurement of caffeine and noncaffeine metabolites (the products of the body breaking down coffee). NAFLD was assessed using the FLI and a scanning measure of fibrosis.
Overall, no associations appeared between self-reported coffee intake and NAFLD measures. However, urine caffeine metabolite levels were significantly higher among individuals with no liver fibrosis, compared with those with fibrosis, and noncaffeine metabolites showed a significant negative association with FLI measures.
In a multiple regression analysis of 89 individuals with type 2 diabetes, both caffeine and noncaffeine metabolites were negatively associated with FLI, which suggests less severe NAFLD, the researchers noted.
Although the mechanism of action remains unclear, the findings suggest that other noncaffeine coffee components such as polyphenols may reduce the risk of fibrosis by reducing oxidative stress on the liver, they said.
Benefits beyond caffeine
“The main surprise of the study was that both caffeine and noncaffeine metabolites had beneficial effects,” Dr. Jones said. “We had anticipated caffeine, based on its well-known effects on inhibiting liver fibrosis, but the effects of other components were less well described.”
Clinicians can encourage their patients with type 2 diabetes who drink coffee to continue to do so within a normal range (up to three to four cups per day) including decaffeinated coffee; however, “they should be strongly encouraged to drink coffee without added fats and sugars, otherwise the protective benefits [against more severe NAFLD] will not be realized,” Dr. Jones said.
Additional research is needed to extend the analysis to include more coffee compounds, especially those truly unique to coffee, since caffeine can be found in many other foods and beverages, Dr. Jones added.