Despite being the most frequent cause of chronic liver disease globally, NAFLD lacks pharmaceutical therapy and dietary recommendations to address its severe health consequences. NASH worsens cirrhosis and hepatocellular carcinoma, resulting in higher medical costs, financial losses, and a worse quality of life. Dietary adjustments, lifestyle changes, and lifestyle modifications are examples of treatment options. Metabolic syndrome, obesity, cardiovascular disease, hypertension, diabetes, and chronic renal disease have all been associated with NAFLD. The current longitudinal study investigates the relationship between plant-based diet index (PDI) and NAFLD risk and whether this association is influenced by genetic factors. All relevant data were obtained from the UK Biobank, comprising over 500,000 participants from England, Scotland and Wales between the ages of 37 and 73.
The current study included participants who underwent at least one dietary assessment and excluded those diagnosed with NAFLD, cirrhosis or other liver diseases. Individuals diagnosed with alcohol-related problems were also excluded. Participants with incomplete genetic data or not of European descent were not considered in this study. Data related to the dietary patterns of the selected participants from the UK Biobank were obtained using the Oxford WebQ, a 24-hour dietary recall questionnaire. Different food types were categorized into seventeen groups, which were sub-classified into three larger categories, including healthy plant-based food, less healthy plant-based food, and animal-based food. Overall PDI, healthful plant-based diet index (hPDI), and unhealthful plant-based diet index (uPDI) were estimated using the study cohort. A total of 159,222 participants were included in the NAFLD risk analyses and 20,692 in liver fat content analyses.
The mean age of the participants was 58 years, and about 58% of the cohort was female. The overall PDI ranged between 25 and 74, hPDI ranged between 27 and 82, and uPDI ranged between 27 and 78. Female, educated, non-current smokers, and non-obese participants were likelier to have a higher overall PDI and hPDI but lower uPDI. Liver fat content was assessed based on magnetic resonance imaging-derived proton density fat fraction (MRI-PDFF) data. A greater consumption of PDI, particularly nPDI, was associated with lower NAFLD risk and liver fat content. Comparatively, higher uPDI was linked to a greater risk of NAFLD and liver fat content. Improved diet quality, which a Mediterranean diet score could represent, influenced the genetic risk of NAFLD on the liver fat content increase. The study findings highlight that PDIs might mediate NAFLD genetic risk.
Consumption of nuts, tea, and coffee was associated with a reduced risk of NAFLD. Consistent with previous reports, a higher intake of hPDI significantly increases the ingestion of flavonoids, dietary fibers, caffeine, phytosterols, and plant proteins. This elevated amount of phytoconstituents leads to improved insulin resistance, gut microbiome composition, and decreased central obesity, which significantly reduces the risk of NAFLD. In this review, researchers have discussed various dietary strategies for managing NAFLD. They conducted searches in databases like MEDLINE, Web of Science, Google Scholar, and Scopus from January to July 2023. Diet plays a significant role in the development of NAFLD because it can impact DNA homeostasis and telomere biology. Proper DNA production and repair depend on the presence of essential nutrients like folate, calcium, retinol, vitamin E and nicotinic acid.
Conversely, trans fats have the potential to cause DNA damage. In NAFLD, there is a noticeable phenomenon of telomere shortening, which can be The Mediterranean Diet (MedDiet) is a predominantly plant-based eating pattern rich in monounsaturated fatty acids (MUFAs) and low in red meat consumption. Research suggests that individuals who follow a high-fat Western diet are more prone to developing NAFLD. MedDiet distinguishes itself from other diets by its low carbohydrate intake, avoidance of refined carbohydrates, and minimal sugar consumption, with a focus on using olive oil as the primary source of added fats. Studies have shown that MedDiet is associated with a reduced risk of NAFLD, as well as a decrease in weight gain and insulin resistance, due to fiber, omega-3 fatty acids and vegetables into its protocol.
Conversely, high-glycemic index carbohydrates, processed meats, and saturated fats tend to accelerate telomere shortening. Protein PNPLA3 plays a crucial role in regulating the accumulation of fat in the liver and the development of NAFLD. Diets rich in carbohydrates and fatty acids can lead to the production of specific proteins encoded by this mutant gene. Consequently, diet has the potential to alter how the liver utilizes lipids, affects insulin resistance, influences oxidative stress, and impacts mitochondrial function through epigenetic changes. Deficiencies in nutrients such as betaine, choline, folate and vitamin B12 may promote DNA methylation, which, in turn, can boost the production of hepatic triglycerides. Thus, the inclusion of foods like nuts, seeds, seafood, and high-fiber diets can significantly reduce the risk of developing NAFLD.
Fish can produce omega-3 fatty acids, which can help reduce fat accumulation in the liver and prevent the development of NAFLD, nonalcoholic steatohepatitis (NASH) and fibrosis. High-fiber diets and whole grains can influence the composition of gut microbiota, potentially affecting the communication between the gut and the liver in NAFLD development. A diet rich in legumes, such as peas, lentils and beans, is strongly associated with a decreased risk of NAFLD. While the exact mechanism behind the protective benefits of vegetables and fruits against NAFLD risk is not fully understood, it is thought to be related to their lower energy density after their addition to the diet and the antioxidant properties derived from polyphenols and carotenoids found in these foods.
Nuts have been shown to have a positive effect on lipid profiles, liver health, and inflammation, potentially serving as an effective treatment for NAFLD. Thgey contain micronutrients associated with NAFLD like zinc, copper, iron, selenium, magnesium, vitamins A, C, D, and E, as well as carotenoids. These micronutrients are known for their antioxidant, antifibrotic, immunomodulatory, and lipoprotective properties, which are reported as mechanisms of action in mitigating NAFLD. Dairy products, especially yogurt containing Lactobacillus acidophilus La5 and Bifidobacterium lactis Bb12, have been linked to a reduced risk of NAFLD due to their high whey protein content, which aids in weight reduction and reducing fat mass. Probiotics have been demonstrated to decrease inflammatory damage in the liver while reducing hepatic triglycerides and steatosis.
Collectively, a plant-based food intervention is pivotal in either avoiding and reversing NAFLD; data indicate that Mediterranean and vegetarian styles may be the best choice thanks to bioactive substances that regulate gut microbiota and liver metabolism. Fermented foods are adviced as well for their antinflammatory and balancing effects on the gut communities. Though taste and choice “exceptions” are tolerated, the main point is not to let them become the rule.
- Edited by Dr. Gianfrancesco Cormaci, PhD, specialist in Clinical Biochemistry.
Scientific references
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