Study Evaluates Link Between Diet, Hepatic Health

Results of a nationally representative cross-sectional study showed no link between transient elastography parameters and an anti-inflammatory diet profile. However, the findings, published in the Journal of Human Nutrition and Dietetics, did reveal an association between higher proinflammatory properties of diet and poorer hepatic health based on surrogate markers of liver disease.

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease, with an estimated prevalence of around 30% in the United States and Europe. NAFLD is also a predictor of cardiovascular disease events and increased all-cause mortality.

Previous research has indicated a link between dietary factors and hepatic health, but limited evidence exists pertaining to the role of diet quality in the prevention of NAFLD.

“Considering that NAFLD has been associated with a systemic and hepatic proinflammatory state and that inflammatory cytokines and chemokines, including tumor necrosis factor-α, interleukin-6 and high-sensitivity C-reactive protein (hs-CRP), are increased in patients with NAFLD and [nonalcoholic steatohepatitis], it should be hypothesized that an anti-inflammatory diet could lead to an improvement in liver status,” researchers explained.

To assess the anti-inflammatory diet profile measured by the Dietary Inflammatory Index (DII) and its association with liver stiffness measurement (LSM) and controlled attenuation parameter (CAP)—measured via transient elastography—investigators carried out a cross-sectional study using data from the population-based National Health and Nutrition and Examination Surveys (NHANES).

A total of 4189 NHANES participants with data recorded between 2017 and 2018 were included in the analysis. In addition to liver disease and diet parameters, researchers also analyzed comorbidity data on hypertension, low high-density lipoprotein (HDL) cholesterol, obesity, and diabetes. Aspartate transaminase:alanine transaminase (AST:ALT) ratio, the fatty liver index (FLI), and the Fibrosis-4 score (FIB4) were also recorded as surrogate measures of NAFLD.

The mean participant age was approximately 51 years and just over half (50.9%) were female.

Analyses revealed:

• Lower DII scores were associated with a lower AST:ALT ratio (P < .001) and FLI (P < .036) after adjusting for covariates.
• Gamma-glutamyl transferase levels (β = 1.702; 95% CI , 0.325-3.080; P = .015), ALT levels (β = −0.616; 95% CI, −1.097 to −0.135; P = .012), AST:ALT ratio (β = 0.025; 95% CI, 0.014-0.036; P < .001), and FLI (β = 1.168; 95% CI, 0.224-2.112; P = .015) were significantly associated with DII in the multivariable-adjusted model.
• Participants in the highest anti-inflammatory tertile had the lowest odds ratio (OR) for NAFLD assessed by FLI in both unadjusted (OR, 0.652; 95% CI, 0.539-0.788; P ≤ .001) and adjusted (OR, 0.722; 95% CI, 0.537-0.972; P = .032) models.
• For the transient elastography parameters (LSM and CAP), no significant associations were identified.

“An anti-inflammatory diet was significantly associated with a lower AST:ALT ratio and FLI after adjusting for potential covariables, supporting the influence of dietary inflammatory potential on liver status,” the authors wrote. In addition, “participants that consumed a proinflammatory diet had an increased risk of NAFLD assessed by FLI as a surrogate marker, suggesting that diet-induced inflammation may increase the development of NAFLD,” they noted.

As causality cannot be determined from the study’s cross-sectional nature, future longitudinal studies are warranted, the researchers wrote. Dietary intake was also assessed via a 24-hour recall, marking a limitation to the study, and the precise prevalence of NAFLD was unknown as no liver biopsies were carried out.

“Strategies to promote an anti-inflammatory diet should be considered to prevent NAFLD in adults,” the authors concluded. “Future intervention studies investigating the effect of dietary inflammatory potential on LSM and CAP are required.”

Reference

Ramírez-Vélez R, García-Hermoso A, Izquierdo M, Correa-Rodríguez M. The dietary inflammatory index and hepatic health in the US adult population. J Hum Nutr Diet. Published online November 15, 2021. doi:10.1111/jhn.12962