Dietary Sources of Fructose and Its Association with Fatty Liver in Mexican Young Adults

Nutrients 2019, 11, 522; doi:10.3390/nu11030522 —

Cantoral A, Contreras-Manzano A, Luna-Villa L, et al.

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Objective

  • To assess the consumption of dietary fructose according to: 1) classification of hepatic steatosis by two indexes and 2) diagnosis of NAFLD by MRI.

Background

  • Previous studies have shown that consumption of fructose through soft drinks and other beverages is higher in NAFLD patients than in controls.
  • Mexico has one of the highest per capita intake of soft drinks worldwide and their consumption is particularly high in the 19 to 29 year-old age group.
  • The present study sought to compare the intakes of different dietary sources of fructose in relation to two liver indexes that predict hepatic steatosis and the identification of NAFLD by MRI in young adults in Mexico.

Methods

  • A cross-sectional analysis was performed in a sample of 100 healthy young adults living in Mexico City between October of 2016 and May of 2017. Participants were selected from the Early Life Exposure in Mexico to Environmental Toxicants (ELEMENT) cohort study.
  • For the present study, participants were evaluated during a weekend day at the research center after 10 hours of fasting. A blood sample and anthropometric measures were obtained. In order to estimate the hepatic triglyceride content, proton magnetic resonance spectroscopy (PMRS) was performed. Also, a trained nutritionist administered a validated semi-quantitative food frequency questionnaire (FFQ) and a lifestyle questionnaire.
  • Measurement of liver fat content and diagnosis of NAFLD was made by MRI, and a fasting blood sample was obtained to quantify glucose, triglycerides and hepatic enzymes (ALT, AST, GGT) using a bench clinical chemistry analyzer.  The Hepatic Steatosis Index (HSI) was estimated using the ALT/AST ratio, BMI, sex, and impaired fasting glucose (IFG) blood levels (>110 mg/dL).

Findings

  • The study sample had a mean age of 21 years, 54% were male, 52% were classified as low SES and 56% of participants were not physically active.
  • According to the MRI, 18% of the participants had the diagnosis of NAFLD (>5% of triglyceride content in the hepatocytes), and according to HSI and FLI, 44% and 46% of the participants presented hepatic steatosis, respectively.
  • The comparison between the true positive participants and the healthy participants showed that the true positive participants had an elevated risk in almost all the parameters in a higher level.  When comparing those classified as false positive versus those in the healthy category, BMI was 2.3 to 3 times higher in the false positive group according to the HSI and FLI, respectively.
  • For the false positive participants in the FLI the risk is significantly higher in the variable ALT (RRR = 1.10, 95%CI 1.02–1.20) compared to healthy participants.
  • For the total sample, dietary information showed that the median energy intake was 2689 Kcal with approximately 56% of the calories from carbohydrates, 33% from lipids, and 13% from proteins. The median intake of SSB was 720 mL, with the main contributor to SSB being soda (specifically cola-type) which contributed 45% of the total SSB, followed by sugar-sweetened commercial fruit beverages and home-made fruit beverages with 22%.
  • Those with negative FLI (score < 30) consumed statistically less energy (kcal) and total grams of carbohydrates per day, but also reported consuming more calories from proteins and lipids as a percentage of the total calories, compared to those classified as positive FLI (score ≥ 30) and also compared to those classified as false positives.
  • The dietary intake of almost all dietary sources of fructose were higher in those classified with steatosis by both indexes. 
  • When the consumption of the different beverages included in the SSB category was compared, the soda intake was statistically higher in FLI false positive than in negative subjects.  In the case of those classified as NAFLD, the median intake of natural fruit juices was statistically higher compared to those classified as non-NAFLD (146 versus 0 mL/day).

Conclusions

  • Sugar-sweetened beverages (SSB) and juices were consumed significantly more by those with steatosis by FLI and NAFLD suggesting that SSB intake is linked to metabolic alterations that predict the risk of having NAFLD at a young age.
  • This study adds to the existing evidence linking SBB intake with NAFLD, a disease that is increasing in Mexico.  Therefore, more public health action is needed to reduce the intake of fructose, as sucrose or HFCS, especially from SSB that are highly consumed in Mexico and in other populations.
  • As obesity is currently one of the biggest health problems in Mexico, and it is related to the incidence of NAFLD, more studies are needed to measure the prevalence of NAFLD in relation to dietary components.

Points to Consider

  • The limited sample size and the cross-sectional nature of this analysis limits the ability to draw conclusions regarding the effect of increased fructose consumption, mainly through SSB, on the natural history or progression of NAFLD in this population.
  • It is possible that other lifestyle factors, such as overall diet, obesity and sedentary behavior, may have an equal of higher effect on NAFLD classification. Given the design of this study, it is not possible to isolate the effect of a single factor. Further, no conclusions about cause and effect can be drawn.
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