Eating your greens could trump genetics in fighting fatty liver disease, new study suggests

By Dr. Priyom Bose, Ph.D.Reviewed by Benedette Cuffari, M.Sc.Sep 19 2023

A recent BMC Medicine study investigates the association between a plant-based diet and genetic predisposition with the risk of non-alcoholic fatty liver disease (NAFLD).

Study: Plant-based diets, genetic predisposition and risk of non-alcoholic fatty liver disease. Image Credit: zarzamora / Shutterstock.com

Background

NAFLD is among the most common chronic liver disorders, affecting around 32.4% of adults worldwide. In the United Kingdom, one in every three people is diagnosed with NAFLD.

NAFLD occurs as a consequence of an interaction between environmental and genetic factors. In fact, several studies have shown that diet is a modifiable risk factor for NAFLD.

A higher consumption of plant-based foods reduces the risk of NAFLD and liver fat content; however, not all plant-based foods are beneficial for NAFLD. For example, the consumption of refined grains, sugar-sweetened beverages, and fruit juices increases the risk of NAFLD.

Most of the studies correlating these food products with NAFLD risk included a small sample size, which limits the understanding of the actual effectiveness of this diet on NAFLD risk. Thus, there is a need for extensive population-based studies to understand what type of plant-based diet can reduce the risk of NAFLD.

Although multiple NAFLD-associated loci have been identified in genomic studies, no studies have assessed the interaction between genetic predisposition and diet patterns that may influence the risk of NAFLD.

About the study

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 U.K. 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 U.K. 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.

Study findings

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.

A significant multiplicative interaction between PDIs and NAFLD-polygenic risk score (PRS) was noted, which increased the risk of NAFLD in those with an hPDI in a sex-specific manner.

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.

Conclusions

The current longitudinal study has some limitations, including a dietary assessment based on 24-hour recall, which is subjected to bias and misclassification. Furthermore, limited data on long-term dietary habits was available. Since this study only included European participants, the generalizability of the findings was limited.

Despite these limitations, the current study reported the interplay between genetic factors and PDIs, which influenced NAFLD risks. Higher hPDI food consumption reduced the risk of NAFLD, irrespective of genetic susceptibility, which is comparable to higher uPDI, which increased the risk of NAFLD.

The study findings emphasize the importance of adhering to a healthy plant-based diet to reduce the risk of NAFLD in the entire population, irrespective of genetic susceptibilities.