Discover how a diet packed with flavonoid-rich foods like tea and apples could revolutionize liver health and cut your risk of fatty liver disease.
Study: A flavonoid-rich diet is associated with lower risk and improved imaging biomarkers of nonalcoholic fatty liver disease: a prospective cohort study. Image Credit: Shutterstock AIStudy: A flavonoid-rich diet is associated with lower risk and improved imaging biomarkers of nonalcoholic fatty liver disease: a prospective cohort study. Image Credit: Shutterstock AI
In a recent study published in The American Journal of Clinical Nutrition, researchers assessed associations between a flavonoid-rich diet and non-alcoholic fatty liver disease (NAFLD) incidence and biomarkers.
NAFLD is the accumulation of lipids in the liver without excessive alcohol intake or other causes. It can progress to inflammatory non-alcoholic steatohepatitis, cirrhosis, and fibrosis, leading to the loss of viable hepatic tissue and, eventually, liver failure. Its global prevalence has increased by over 50% in the past three decades. Principal treatment options include cardiovascular disease risk reduction, primarily through weight loss; however, this might not be appropriate for all individuals.
Therefore, prophylactic and therapeutic approaches should focus on lifestyle and nutritional interventions. A plant-based diet characterized by a high intake of whole grains, fruits, and vegetables is beneficial for several cardiometabolic outcomes. Plant foods contain high levels of flavonoids. Flavonoids are bioactive compounds that can reduce inflammation, improve insulin sensitivity, and modulate lipid metabolism. Higher intake of flavonoids has been associated with augmented cardiometabolic health. However, there is limited research on flavonoids regarding NAFLD.
About the study
Broad Dietary Sources: Foods with high flavonoid content include not only tea and apples but also parsley, onions, citrus fruits, blueberries, and even the skin of peanuts, demonstrating their ubiquity in both common and niche foods.
In the present study, researchers assessed associations of flavonoid-rich diet with NAFLD incidence and imaging biomarkers of steatosis and liver fat in the United Kingdom (UK) Biobank cohort. More than 500,000 individuals aged 40–69 years were recruited from 2006 to 2010 in England, Wales, and Scotland. Baseline assessments were performed; additional data were obtained during 2009-12 through Oxford WebQ 24-hour dietary assessments.
Additional biomarkers were measured at follow-up, including magnetic resonance imaging (MRI)-based body composition biomarkers. The researchers investigated associations of flavonoid intake indices with incident NAFLD and imaging-derived NAFLD biomarkers. Flavonoid intake indices were flavodiet score (FDS), flavonoid subclasses, and flavonoid-rich foods. FDS, a measure of flavonoid consumption, included servings of tea, apples, berries, grapes, onions, and dark chocolate, among other foods. All dietary data were sourced from the Oxford dietary assessments.
Incident NAFLD was determined from the International Classification of Diseases, Tenth Edition (ICD-10) data linked to inpatient records. Participants were followed up until NAFLD diagnosis, other competing diagnoses, or death. Liver fat was measured as proton density fat fraction. Liver-corrected T1 (cT1) values, a marker for steatosis, were also derived. Cox proportional hazard regression models were used to assess hazard ratios of NAFLD risk. Multivariable linear regression was used for analyses of flavonoid exposures and imaging-derived biomarkers.
Findings
Unique Metabolism of Flavonoids: Flavonoids are poorly absorbed by the human body, with less than 5% absorption, and are rapidly metabolized into smaller fragments, many of which have unknown properties but contribute to their health effects.
Overall, the study included 121,064 adults aged 59 years, on average. Most participants were female (56%) and had a high educational status (63%). The average body mass index (BMI) was 26.7 kg/m2. When stratified into FDS quartiles, participants in the lowest quartile were younger, more likely to be smokers, and had lower education than those in the highest quartile.
In total, 1,081 NAFLD cases were identified over an average of 10 years of follow-up. The FDS was inversely associated with the risk of NAFLD; the highest FDS quartile was significantly associated with a 19% lower risk of NAFLD compared to the lowest quartile (hazard ratio: 0.81, 95% confidence interval: 0.67–0.97). In food-based analyses, higher consumption of apples and tea was associated with 22% and 14% reduced NAFLD risk, respectively, compared to lower consumption levels.
Based on flavonoid subclasses, the highest quartile of theaflavin and thearubigin, proanthocyanidin, flavan-3-ol, and flavonol was associated with a lower NAFLD risk than the lowest quartile. Participants in the highest FDS quartile had a significantly lower percentage of liver fat (–5.28%) than the lowest quartile participants. Consistently, individuals with high intakes of apples and tea had a lower liver fat content than those with low intakes.
Participants in the highest FDS quartile showed significantly lower cT1 values (–1.73%) than those in the lowest quartile. A high red wine and tea consumption was inversely associated with cT1 values. However, higher grape intake was linked to elevated cT1 values, potentially due to its sugar content. Further, a high intake of dark chocolate was associated with lower liver fat, but a high intake of grapes and onions was associated with higher liver fat content.
Conclusions
The findings reveal that a higher FDS and intake of specific flavonoid-rich foods were associated with a reduced risk of NAFLD and lower imaging-derived cT1 values and liver fat. Further, there were unexpected positive associations between grapes, onions, anthocyanins, and liver fat, albeit weak in magnitude. These findings may reflect confounding dietary factors, such as the sugar content in grapes and the high-fat meals often paired with onions.
Overall, the study contributes to the growing literature suggesting possible protective effects of flavonoids on NAFLD and its progression. Further research is warranted to explore mechanistic pathways and confirm these findings across diverse populations.
Journal reference:
Bell W, Jennings A, Thompson AS, et al. A flavonoid-rich diet is associated with lower risk and improved imaging biomarkers of nonalcoholic fatty liver disease: a prospective cohort study. The American Journal of Clinical Nutrition, 2024, DOI: 10.1016/j.ajcnut.2024.09.022, https://www.sciencedirect.com/science/article/pii/S0002916524007913