Can an apple a day keep Nonalcoholic Fatty Liver Disease (NAFLD) away?

Aim

The prevalence of nonalcoholic fatty liver disease (NAFLD) has increased by over 50% in the last 30 years, with over 32% of the global adult population affected. NAFLD is lipid accumulation in the liver of >5% in the absence of excessive alcohol consumption or other cause. 

Underlying factors such as obesity and sedentary lifestyle can lead to the development of NAFLD. Therefore, preventative and treatment should focus on nutrition and lifestyle interventions.

NAFLD is a metabolic disorder that is closely linked to cardiometabolic abnormalities. In population-based studies, a higher intake of several flavonoid subclasses has been associated with better cardiometabolic health.

Using UK Biobank data, the aim of this study was to assess the association between a flavonoid rich diet with incident NAFLD. 

Method

UK Biobank is a prospective population-based cohort study that includes data from half a million men and women (ages 39 to 72) recruited from the general population between 2006 and 2010. The data includes detailed information on demographics, social, lifestyle, physical activity, medical history, hospital records and mortality.

The authors analysed the data from the Oxford WebQ 24-h dietary assessments in 2 parts. Firstly, they show correlations between three flavonoid intake indices (a flavodiet score (FDS), flavonoid-rich foods, flavonoid subclasses) and incident NAFLD. Secondly, they show correlations between the same flavonoid indices and NAFLD imaging biomarkers gathered during imaging follow-up.

The FDS is calculated by adding up the daily servings of foods high in flavonoids. Foods in the FDS are tea (black and green, capped at 4 servings per day), apples, berries, red wine, grapes, sweet peppers, onions, dark chocolate, oranges (including satsumas), and grapefruit. 

Key findings

The mean (SD) age of the participants was 59.0 (7.9) y, 55.9% of participants were female, 63.0% had attained a “high” educational status, and the mean (SD) BMI was 26.7 (4.6).

Over a mean follow-up period of 10 years, 1081 cases of NAFLD were identified.

The FDS demonstrated a linear inverse association with NAFLD, with the highest quartile of the FDS being associated with a statistically significant 19% lower risk for NAFLD compared to the lowest [HR (95% CI): 0.81 (0.67, 0.97), p-trend 0.02].

High apple intake was associated with a 22% lower risk of NAFLD compared to low intakes [HR (95% CI): 0.78 (0.67, 0.92), p-trend <0.01]. No significant associations were observed with red wine, berries, or less commonly consumed flavonoid-rich foods.

Liver fat concentration was lower in those who had a higher intake of tea and apples compared to those who consumed less (tea: relative difference low compared with high –6.60%, p-trend <0.001); apple: relative difference low compared with high –4.38%, p-trend <0.001).

Conclusion

This analysis demonstrates that a lower risk of developing NAFLD and a smaller amount of imaging-derived liver fat is linked to a greater FDS and consumption of several flavonoid-rich foods, such as apples and tea.

NAFLD is thought to be driven by insulin resistance, impaired lipid metabolism, and inflammation. Lipid accumulation, alongside oxidative stress and inflammatory signalling is thought to be a key driver of NAFLD progression.

Foods high in flavonoids and their isolated components reduce inflammation, lower insulin resistance, and alter lipid metabolism, which lowers low-density lipoprotein and triglycerides.

This study adds to a growing body of literature that eating a diet high in flavonoids could have a protective effect on the development and progression of NAFLD.

Save article as PDF

Save article as PDF