High-Protein Diet for Improving Alcoholic Fatty Liver Disease

Plain-language summary

Alcohol-associated liver disease (ALD) is a major cause of mortality from malignant liver diseases, accounting for 47.9% of cirrhosis-related deaths and 30% of liver cancer-related deaths annually. In China, both alcohol consumption and the prevalence of ALD (approximately 5.15%) are on the rise, making ALD an increasingly significant health concern for the population. Alcohol-associated fatty liver disease (AFLD), as the initial and most reversible stage of ALD, is primarily characterized by excessive hepatic lipid deposition, mild liver injury accompanied by mild inflammation. It can progressively develop into alcoholic hepatitis, and in some patients, advance to liver fibrosis, cirrhosis, and even hepatocellular carcinoma. Currently, there is a lack of effective clinical treatments for AFLD. Although alcohol abstinence remains the optimal choice for reversing AFLD, it is often difficult for individuals with alcohol dependence to maintain. A high-protein diet generally refers to a dietary pattern where protein accounts for more than 20% of total energy intake. A protein contribution of 30% is a common ratio in research investigating high-protein dietary interventions for metabolic diseases. Population-based intervention studies have demonstrated that a high-protein diet at this ratio significantly reduces hepatic fat content. For instance, a study published in Gastroenterology (2017) reported that a 6-week isocaloric high-protein diet (macronutrient distribution: 30% protein, 40% carbohydrates, 30% fat) significantly improved hepatic lipid deposition in patients with non-alcoholic fatty liver disease (NAFLD) and type 2 diabetes mellitus (T2DM). Research in Diabetologia (2019) showed that a 6-week isocaloric high-protein diet (30% protein, 30% carbohydrates, 40% fat) significantly reduced hepatic fat content in patients with T2DM. Additionally, a study in Liver International (2020) indicated that a 3-week energy-restricted high-protein diet (30% protein, 35%-45% carbohydrates, 25%-30% fat) significantly decreased hepatic fat content in NAFLD patients. Importantly, none of the aforementioned studies reported adverse events associated with the high-protein dietary interventions. Furthermore, a population-based intervention study published in Annals of Internal Medicine revealed that a low-carbohydrate, high-fat diet was more effective than a high-carbohydrate, low-fat diet in reducing hepatic fat content over a 6-month period in patients with NAFLD and T2DM. These findings suggest that increasing the percentage of energy from protein by reducing carbohydrate intake may yield superior improvements. Based on the macronutrient distributions from the referenced population interventions, and considering that a 30% fat energy contribution closely aligns with the typical dietary fat intake of the Chinese AFLD population, we established the macronutrient distribution for the high-protein diet group as 30% protein, 40% carbohydrates, and 30% fat. This study intends to conduct a randomized controlled trial to investigate the effects of increasing the percentage of energy from protein under an isocaloric dietary pattern on liver function, hepatic fat content, and glucose-lipid metabolism in individuals with AFLD. The aim is to elucidate the mechanisms underlying its beneficial effects on AFLD, thereby providing population-based evidence and strategies for health promotion in this patient group.

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