For patients with nonalcoholic fatty liver disease (NAFLD) who supplement their diets with polyunsaturated fatty acids (PUFA), liver and metabolic parameters improve, results of a systematic review and meta-analysis suggest.
Data from randomized clinical trials show that, for participants with NAFLD who used PUFA supplements with or without additional dietary interventions, hepatic steatosis and lobular inflammation decreased, and in one study, fibrosis decreased. There were also improvements in liver enzyme levels, said Saleh Alqahtani, MBChB, associate professor of medicine at Johns Hopkins University, Baltimore, during a presentation at the annual meeting of the American Association for the Study of Liver Diseases.
“Since there’s no effective medical therapy for NAFLD, weight loss through lifestyle modifications becomes the most important focused intervention for patients with NAFLD,” he said. “However, the majority of patients fail to achieve or to maintain weight loss for long-term therapy. Therefore, dietary intervention or supplementation might help reduce the prevalence of NAFLD and decrease the progression of nonalcoholic steatohepatitis [NASH] and liver cirrhosis.
“More clinical trials are warranted to determine the long-term efficacy of the Mediterranean diet and polyunsaturated fatty acid supplementation among adult patients with NAFLD,” he added.
RCTs and case-control studies
It’s well documented that consumption of PUFAs, found in fatty fish and in canola, grapeseed, corn, and soybean oils, as well as monounsaturated fatty acids, found in olive oil and peanut oil, can contribute to improvement of NALFD, Dr. Alqahtani said.
In contrast, foods high in saturated fatty acids, such as butter, as well as trans fats and cholesterol can contribute to NAFLD progression, he said.
In their studies of intrahepatic triglyceride content, Dr. Alqahtani and colleagues found that fatty acids in the liver come from three major sources: dietary fatty acids, which account for about 15% of liver fat, tissue lipolysis, and de novo hepatic lipogenesis.
Previous systematic reviews and meta-analyses of the relationship between diet and NAFLD have focused on marine-based (n-3) PUFAs, but “the data regarding the evidence of unsaturated fatty acids through supplements or monounsaturated fatty acids through dietary supplementation are lacking,” he said.
To summarize the effects of dietary or supplemental fatty acids on liver and metabolic parameters in adults with NAFLD, Dr. Alqahtani and colleagues conducted a systematic review and meta-analysis, concentrating on studies that included specifics about interventions and outcomes.
They identified a total of 18 randomized controlled trials and 4 case-control studies that met their criteria. The studies were published from 2008 to 2020.
Regarding the effects of interventions on the components of NASH, they found that, in 1 or more of 12 randomized trials of PUFA supplementation with or without dietary interventions, there were associations with decreased hepatic steatosis, lobular inflammation, and fibrosis and declines in ALT and AST levels.
In three trials of dietary-only interventions, there were decreases in hepatic steatosis and ALT and/or AST levels. In two studies of the effects of healthy cooking oils only, hepatic steatosis decreased, but there was no effect on ALT or AST levels.
All three interventions were associated with improvements in fasting glucose levels and insulin metabolism, as well as decreases in total cholesterol, triglycerides, and LDL cholesterol and increases in HDL cholesterol.
Better understanding of dietary composition
“We’ve known for a while that dietary composition may impact NAFLD and NASH,” said Manal F. Abdelmalek, MD, professor of medicine at Duke University, Durham, N.C., who commented on the study.
“What [Dr. Alqahtani and colleagues] have shown is that supplementation with healthy fatty acids improves fatty liver. This really does extend our knowledge of what we understand about dietary composition, particularly the recommendations that support higher fish consumption and a Mediterranean-style diet,” she said.
“It’s not just about the fat but the type of fat that’s consumed, and drilling down to the particulars of dietary composition beyond calories alone,” she added.
No source of funding for the study has been disclosed. Dr. Alqahtani and Dr. Abdelmalek have reported no relevant financial relationships.
A version of this article first appeared on Medscape.com.