Study links ultra-processed foods to higher metabolic disease risk

A recent Frontiers in Nutrition study assesses the association between metabolic diseases and the consumption of ultra-processed foods (UPFs). 

Study: Ultra-processed food consumption and metabolic disease risk: An umbrella review of systematic reviews with meta-analyses of observational studies. Image Credit: JeniFoto / Shutterstock.com

Background

Reducing the consumption of UPFs is typically recommended to prevent the development of metabolic diseases like type 2 diabetes mellitus (T2DM) and obesity. Metabolic diseases adversely affect organs, tissues, or cells and are caused by the decomposition and abnormal synthesis of certain substances during metabolism.

The precise etiology of metabolic diseases remains unclear. Nevertheless, both environmental and genetic factors influence their occurrence, among which diet is an easily modifiable environmental factor.

The NOVA food classification system defines UPFs as a class of foods arising from industrial formulations created from extracted substances, additives, and little intact food. Examples of UPFs include cakes, snacks, sausages, and sweetened beverages.

Research has identified an association between various metabolic diseases and UPF consumption. However, some question this association, claiming that these relationships established in the literature are prone to biases.

About the study

The present study involved an umbrella review (UR), in which published systematic reviews were analyzed with meta-analyses to assess their credibility and validate the robustness of the relationship between metabolic disease and UPF consumption.

The Web of Science, PubMed, Embase, and Cochrane Library databases were systematically searched until July 15, 2023. Language restrictions were not imposed, and citations of included studies were monitored to detect additional eligible studies.

Articles involving laboratory and animal studies, as well as genetic polymorphisms, were excluded. Additionally, studies unable to obtain study-specific data, those without quantitative evaluations, and those that included fewer than three original studies were excluded from the meta-analyses. 

Key findings

An extensive overview of 13 meta-analyses was performed to evaluate the credibility of relationships between the consumption of UPFs and metabolic disease. To this end, all studies suggested that the consumption of UPFs was associated with the development of obesity and T2DM. 

The highest level of UPF consumption and a 1.55-fold higher obesity risk were established in seven cross-sectional studies and several prospective cohort studies; therefore, UPF consumption could be considered a risk factor for obesity. These findings indicate that there may be health benefits associated with reducing the consumption of UPFs. This should be considered in the future by healthcare professionals and policymakers while formulating dietary guidelines.

Two meta-analyses revealed a significant association between UPF consumption and T2DM, thus suggesting that consuming UPFs could be a risk factor for developing T2DM. Within UPFs, processed meat and sugar-sweetened beverages were strongly related to the risk of T2DM, with the dose of these UPFs potentially dictating this association.

In the moderate and lowest meta-analysis, the association between T2DM and UPFs was supported by weak evidence. This association was insignificant in the Asian population. 

The consumption of UPFs was also associated with an increased risk of non-alcoholic fatty liver disease (NAFLD), hypertension, and metabolic syndrome (MetS). However, these associations were not robust across subgroups, which necessitates the need for additional studies to explore these associations.

Conclusions

The current study provides evidence that the consumption of UPFs is associated with a greater risk of metabolic diseases, particularly obesity and T2DM. For other metabolic diseases, the associations should be explored further in future studies.

The main strength of this study is the comprehensive assessment of the quality and credibility of each meta-analysis. In fact, this is the first UR to offer an extensive summary of the association between metabolic diseases and UPF consumption.

One limitation of this study could be due to underlying studies lacking specific data or the exclusion of studies by previous meta-analyses. Future studies should address this concern by including other outcome variables, such as hyperuricemia and dyslipidemia. Residual confounding and measurement errors were also not considered due to the lack of randomized controlled trials. 

Few underlying studies used the NOVA classification system to define UPFs, and some meta-analyses simultaneously included studies that used the NOVA system and those that did not. This made it difficult to maintain consistency while reporting findings and could have led to the misclassification of UPFs.

The generalizability of the results could be questioned, as most studies were conducted in the United States, across several European countries, and Brazil.