Freshwater fish-based diet eases liver steatosis in NAFLD patients

Adherence to a freshwater fish-based diet helps regulate the gut microbiota and its metabolites, suggesting benefits in individuals with nonalcoholic fatty liver disease (NAFLD), reveals a study.

On the other hand, consumption of a similar total of animal protein and fat from the alternating freshwater fish and red meat does not seem unsafe in the dietary management of NAFLD patients.

“[T]his 84-day randomized, controlled pilot study in participants with NAFLD showed that the freshwater fish-based diet induces a greater improvement in hepatic steatosis and other metabolic phenotypes by regulating gut microbiota and its metabolites compared with the alternating freshwater fish-based and red meat-based diet, independent of weight change,” the researchers said.

Using a computer-generated random number allocation by a researcher not involved in this study, 34 NAFLD patients with hepatic steatosis ≥10 percent were randomized to the fish (F) group or the alternating fish and meat (F/M) group. Liver fat content and gut microbiota and its metabolites were then measured.

Patients in the F group had significantly greater absolute reduction of hepatic steatosis at the end of intervention than those in the F/M group (‒4.89 percent vs ‒1.83 percent; p=0.032). [Am J Gastroenterol 2022;117:1621-1631]

Sixteen secondary outcomes were also assessed: levels of body weight, waist circumference, body mass index, fasting blood glucose, fasting insulin, alanine aminotransferase, aspartate aminotransferase, γ-glutamyl transpeptidase, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, interleukin-6, tumour necrosis factor-α, C-reactive protein, and ferritin.

Of these, seven improved in the F group, including alanine aminotransferase and gamma-glutamyl transferase, which was greater than in the F/M group. Notably, intake of alternating freshwater fish and red meat in the diet did not worsen NAFLD.

In addition, significantly greater changes in the enrichment of Faecalibacterium, short-chain fatty acids, and unconjugated bile acids and the depletion of Prevotella 9 and conjugated bile acids were noted in the F group compared with the F/M group.

Gut microbiota

A growing body of evidence suggests the important role played by the gut microbiota in the occurrence and development of diabetes, obesity, cardiovascular disease, and NAFLD. [Nature 2012;490:55-60]

“Therefore, we explored the potential involvement of gut microbiota in mediating dietary freshwater fish-induced NAFLD improvement. In the F group, the abundance of Faecalibacterium increased while the abundance of Escherichia-Shigella and Prevotella 9 decreased at the end of the intervention,” the researchers said.

“However, these results should be considered preliminary, and large-scale controlled studies are required to confirm these findings,” they noted.

Apart from gut microbiota, several metabolites produced by commensal bacteria had been suggested to influence the pathogenesis and progression of NAFLD. [Gut 2019;68:359-370]

“Gut macrobiotic-related metabolites, including short-chain fatty acids (SCFAs), amino acid catabolites, and butyric acids (Bas), regulate hepatic steatosis and inflammation by signaling from their homologous receptors,” the researchers said. “We, therefore, attempted to clarify metabolites (ie, SCFAs and BAs) that potentially mediate the beneficial impact of dietary freshwater fish consumption on NAFLD.”