Light-To-Moderate Alcohol Consumption Tied To Increased Type 2 Diabetes Risk With NAFLD

People with nonalcoholic fatty liver disease (NAFLD) are at increased risk of developing type 2 diabetes when they consume light-to-moderate amounts of alcohol than when they abstain from drinking, a Chinese study suggests.

Researchers followed 7,079 Chinese men, including 1,831 with NAFLD, who underwent annual health system checkups between 2009 and 2018. They included 243 men with type 2 diabetes at baseline and 630 who developed type 2 diabetes during 45,456 person-years of follow-up.

Compared to nondrinkers without NAFLD, adjusted hazard ratios for type 2 diabetes in men with NAFLD were 1.6 for nondrinkers, 2.64 for light drinkers, and 2.69 for moderate drinkers.

Light-to-moderate alcohol consumption (LMAC) was associated with a reduced risk of type 2 diabetes in men without NAFLD, however. In this group, light drinkers were 78% less likely to develop type 2 diabetes, and moderate drinkers had a 54% lower risk, compared to men with NAFLD.

"Our results also showed that light-to-moderate alcohol consumption may prevent type 2 diabetes in lean participants, but not in overweight or obese participants," said senior study author Dr. Chengfu Xu of the First Affiliated Hospital and Zhejiang University School of Medicine, Ningbo, China.

"Our findings suggest that NAFLD patients should not intake light-to-moderate alcohol for the purpose of lowering risk of type 2 diabetes," Dr. Xu said by email.

To assess alcohol consumption, researchers screened habitual and binge drinkers using questionnaires at baseline and during follow-up exams. They asked drinkers to detail how often and how much they drank over the previous 12 months using a questionnaire, then had nurses discuss the responses to confirm what people said.

Researchers excluded people from the study who were binge drinkers or who consumed more than 210 grams of alcohol a week. They categorized participants as light drinkers who drank less than 70g a week, and as moderate drinkers if they drank 70g to 210g a week.

Participants were classified as having type 2 diabetes if they met any of the following criteria: self-reported clinician diagnosed type 2 diabetes; fasting plasma glucose of at least 126 mg/dL; or hemoglobin A1c of at least 6.5%.

They diagnosed NAFLD based on abdominal ultrasound examination, excluding heavy alcohol consumption or other factors that might cause fatty liver.

One limitation of the study is that recall bias might lead to incorrect answers on alcohol consumption questionnaires, the study team notes in the American Journal of Gastroenterology. Researchers also didn’t distinguish between lifetime abstainers and people who were former drinkers.

In addition, the researchers lacked data on some confounding factors like diet and exercise habits. Ultrasound for the diagnosis of NAFLD might not detect some mild cases, the study team adds.

NAFLD is a wide spectrum of liver damage, ranging from simple steatosis to steatohepatitis (NASH) and advanced fibrosis and overt cirrhosis, said Dr. Gianluca Perseghin, a professor of endocrinology at Universita degli Studi di Milano Bicocca, Department of Medicine and Rehabilitation-Policlinico di Monza in Milan, Italy.

"Ultrasound has very poor sensitivity to distinguish the severity of the hepatic disease, therefore within the group of patients with NAFLD at baseline the degree of severity of the hepatic disease is missing (for) patients within the same category (NAFLD) but with large potential difference in the hepatic disease and as a consequence, in (patients’ susceptibility to) the detrimental impact of alcohol consumption," Dr. Perseghin, who wasn’t involved in the study, said by email.

"If you have NAFLD even the low dose of alcohol consumption may be associated with higher risk of future development of diabetes," Dr. Perseghin added.

—Lisa Rapaport

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