Vegan Diet Advice Might Benefit Liver Enzymes in Nonalcoholic Fatty Liver Disease: an Open Observational Pilot Study

The Western diet is rich in saturated fats, refined sugars and meat consistent with a high-energy load and secondary risk of increased metabolic diseases including nonalcoholic fatty liver disease (NAFLD). However, no data are available on potential benefit of vegan diets in NAFLD and/or nonalcoholic steatohepatitis (NASH). We aimed to study prospectively the effect of a vegan diet, excluding all animal products on liver chemistry in a group of consecutive NAFLD patients.

This was a prospective, pilot study run on 40 consecutive patients affected by NAFLD. Eight subjects refused to join the study for poor diet palatability, leaving 32 patients (19 males, mean age 50 years), with abnormal measures of liver function who agreed to adhere to a vegan diet for six months. The caloric intake was tailored by the dietitian to obtain a weight loss ≥5% of body weight in overweight patients [body-mass index (BMI) ≥25] and ranged from 1500 Kcal to 1800 Kcal. Patients were contacted monthly by phone to reinforce diet and lifestyle advice and were seen at the gastrointestinal clinic when doubtful about diet advice.

At six-month follow-up, 6 subjects did not attend the clinic leaving only 26 patients for data analysis. Initial anthropometric values were mean weight 78 kg (range 52-95), mean body mass index (BMI) 26.8 Kg/m2 (range 20.3-31.2). Liver function tests showed mean ALT value 99 U/L (SD±45), mean AST value 54 U/L (SD±44), mean GGT value 160 U/L (SD±122), pre-treatment. After six months mean body weight was 73 Kg (range 52-87), mean BMI was 25.2 Kg/m2 (range 20.3-29.7) (p<0.001 compared to baseline for both parameters). Liver enzymes improved to a mean of ALT value 36 U/L (SD±21), AST value 27 U/L (SD±10) and GGT value 55 U/L (SD±57), respectively (p<0.001 compared to baseline for all enzymes). Normalization of liver function tests as a whole was observed in 20/26 patients (76.9%). A loss of ≥ 5% of body weight was observed in 12 patients (46.1%), but it did not correlate with the normalization of liver function tests (p=0.5).

Our data provide preliminary evidence of improved liver enzymes in NAFLD patients with a strict vegan diet and although our study sample is limited, decreased body weight did not seem critical to the outcome.