I get this question a lot. First off, if the fatty liver is due to alcohol, the answer is no. Your fatty liver may be alcohol related if you consume more than 14 standard drinks (140 g alcohol) per week if you are male, and 7 drinks (70 g) if you are a woman. In this case a diagnosis of NAFLD (non-alcoholic fatty liver disease) cannot be made.
NAFLD and alcohol use
Let’s assume you have NAFLD. Can you drink and how much? The short answer is, we don’t know for sure. Why? Because we don’t have high quality studies. What we have is marred by recall bias as most studies are retrospective. Patients self-reported their alcohol use. We know that patients with alcoholic liver disease often underreport their alcohol intake, NAFLD patients may likewise underreport alcohol intake because they think that alcohol intake can make their disease worse.
A recent important study by Ajmera and colleagues  provides important data showing that modest alcohol use is associated with less improvement in NAFLD histology over 4 years of follow-up. The study is important because unlike previous studies, included patients from a natural history cohort and two drug trials. Still, other studies come to opposite conclusions, i.e., modest alcohol consumption may confer benefits (see table below). All in all, at present we cannot recommend modest drinking in patients with NAFLD to improve liver health.
Table 1. Observational studies on the effect of modest drinking on NAFLD
(from Lee HW, Wong VW-S, Is modest drinking good for the liver?, Clinical Gastroenterology and Hepatology (2018), doi: 10.1016/j.cgh.2018.03.026.)
|Study||Design||Definition of modest drinking||Observation|
|Cross-sectional population study of 11754 community subjects (the Third National Health and Nutrition Examination Survey); suspected NAFLD was defined as ALT >43 U/l||Up to 10 g of alcohol per day||Modest wine drinkers had a lower prevalence of suspected NAFLD than non-drinkers (0.4% vs 3.2%)|
|Cotrim 2009||Cross-sectional study of 132 patients who underwent liver biopsy during bariatric surgery||Group 1: 20-40 g of alcohol per day Group 2: 0-20 g per day
Group 3: Non- drinkers
|Similar proportion of patients in the 3 groups had NASH (89.5% vs 87.5% vs 86.0% had type III and IV histology by the Matteoni classification)|
|Wong 2012||Cross-sectional population study of 922 community subjects using proton- magnetic resonance spectroscopy and transient elastography||Up to 20 g of alcohol per day in men and 10 g per day in women||Modest drinkers were more likely to have fatty liver than non-drinkers (37.8% vs 26.4%), though the association became insignificant after adjustment for age, sex and metabolic syndrome|
|Hamaguchi 2012||Cross-sectional study of 18571 subjects undergoing health checkups; fatty liver was diagnosed by abdominal ultrasonography||40-140 g of alcohol per day||Modest drinkers were less likely to have fatty liver than non-drinkers (26.4% vs 36.5%)|
|Cross-sectional study of 582 biopsy-proven NAFLD in the NASH Clinical Research Network||Up to 20 g of alcohol per day||Modest drinkers were less likely to have NASH (53.2% vs 69.8%) and
fibrosis (70.0% vs 80.1%) than non- drinkers
|Kwon 2014||Cross-sectional study of 77 patients with biopsy-proven NAFLD at an academic center||Patients classified by weekly amount of alcohol consumption||Patients with any alcohol consumption were less likely to have F3-4 fibrosis than non-drinkers (15% vs 36%)|
|Moriya 2015||Longitudinal study of 5297 subjects undergoing health checkups; fatty liver was diagnosed by abdominal ultrasonography||Patients classified by weekly amount of alcohol consumption||In men, drinking of any amount reduced the odds of fatty liver by 21-32%. In women, drinking 0.1-
69.9 g/week and 70.0-139.9 g/week reduced the odds of fatty liver by 29% and 33%, respectively.
|Ajmera 2018||Paired liver biopsies in 187 clinic patients and 98 patients receiving placebo in the PIVENS and FLINT trials||Up to 2 drinks per day||Non-drinkers were more likely to have improvement in steatosis, aspartate aminotransferase level and resolution of steatohepatitis than modest drinkers|
ALT, alanine aminotransferase; NAFLD, nonalcoholic fatty liver disease
 Ajmera V, Belt P, Wilson LA, Gill RM, Loomba R, Kleiner DE, et al. Among Patients with Nonalcoholic Fatty Liver Disease, Modest Alcohol Use is Associated with Less Improvement in Histologic Steatosis and Steatohepatitis. Clin Gastroenterol Hepatol 2018.