Relationship Between Coffee Consumption and NAFLD in Community Studies
Four continuous cycles of the National Health and Nutrition Examination Surveys (NHANES, USA 2001–2008) were used to investigate the effects of dietary behavior in NAFLD patients. Dietary intake was evaluated by questionnaires that included nutrition components. Multivariate analyses were conducted of variables that included demographics, clinical parameters, and nutritional components in relation to presence of NAFLD (defined in this study by elevated aminotransferase, without ultrasonography). Five factors were independently associated with NAFLD: African American race, male gender, obesity, caffeine intake, as well as plain water consumption. These findings show a strong association between coffee consumption and protection against the development of NAFLD (see Table 1). The limitation of the NHANES data analysis is the restricted define of NAFLD; cases with cirrhosis may not have shown elevated ALT.
In an Italian study, 137 NAFLD cases and 108 controls were enrolled, and coffee intake determined by the absolute number of cups of coffee consumed. This was graded as 1 (0 cups of coffee/day), 2 (1–2 cups of coffee/day), and 3 (≥ 3 cups of coffee/day). Insulin resistance was analyzed by homoeostasis model assessment-insulin resistance (HOMA-IR) index. When compared with non-coffee drinkers, those who consumed coffee had less severe fatty liver evaluated by ultrasound "bright liver score" (BLS). Further, obesity, insulin resistance, lower high-density lipoprotein (HDL) cholesterol, older age, and arterial hypertension were associated with a greater risk of more severe grades of BLS, while coffee intake was associated with a lower risk of severe BLS. By multiple regression analysis, coffee use was inversely associated with the degree of "bright liver," while insulin resistance and obesity were directly associated with increased likelihood and severity of BLS on ultrasound. A case–control study from Mexico also found similar protective effects of coffee consumption against NAFLD as assessed by ultrasonography (Table 1). The limitations of these studies are the insensitivity of ultrasound for minor grade of steatosis and possibly for established cirrhosis when steatosis may be resolved.
The association of caffeine consumption with both the prevalence and severity of NAFLD was further established in another study where a validated questionnaire of caffeine consumption was utilized to determine if there was a relationship between caffeine intake and NAFLD severity, this time established by histological examination of liver biopsies. In this study, the authors reported a strong inverse relationship between caffeine consumption and hepatic fibrosis (Table 1).
J Gastroenterol Hepatol. 2014;29(3):435-441. © 2014 Blackwell Publishing