Unpacking ultra-processed foods: Identifying research priorities
Virtual Best Brains Exchange summary

Event description

On June 11-12, 2024, Health Canada’s Food and Nutrition Directorate collaborated with CIHR, the CIHR-Institute of Cancer Research, and the CIHR-Institute of Nutrition, Metabolism and Diabetes to host a Best Brains Exchange (BBE) on the topic “Unpacking Ultra-Processed Foods—Identifying Research Priorities.” Canadian and international researchers, non-governmental research funders, and officials working in food and nutrition research from other federal departments joined Health Canada and CIHR to discuss what is currently known about the relationship between ultra-processed food (UPF) consumption and health, and identify knowledge gaps and research priorities relevant to public health. With a strong signal of a link between UPF consumption and poor health outcomes, and the increasing prominence of UPF in the diets of Canadians, it is important to better understand the link  to inform future food and nutrition policies designed to reduce diet-related health burdens.

Objectives

The Best Brains Exchange Unpacking Ultra-Processed Foods—Identifying Research Priorities was designed to identify knowledge gaps and research priorities regarding the impact of ultra-processed food (UPF) consumption on health. The three objectives were to:

  1. Discuss what is known about UPF consumption and health, including the nature and extent of vulnerability in the population.
  2. Identify critical gaps in evidence to understand the relationship between UPF consumption and health.
  3. Identify priorities for research to address identified gaps.

Background

Ultra-processed foods (UPF) are prominent in the food supply and estimates suggest they represent almost half of all energy consumed in CanadaFootnote 1. In the last decade, research on the association between UPF consumption and health outcomes has steadily increased. The NOVA food classification, including its definition of UPF (“formulations of ingredients, mostly of exclusive industrial use, typically created by a series of industrial techniques and processes”)Footnote 2, is the most common classification applied by researchers around the world investigating the role of UPF and health. Results of several recent systematic and umbrella reviews, which combined and analyzed epidemiological evidence, show consistent signals that higher consumption of UPF is associated with greater risk of adverse health outcomes including overweight, obesity, poor mental health, type 2 diabetes, some cancers and cardiovascular diseases Footnote 3,Footnote 4, Footnote 5. However, the certainty of evidence has been assessed as being low. A randomized controlled trial (RCT) showed that people consumed more calories and gained more weight when eating diets high in UPF than when consuming a diet based on minimally or unprocessed foodsFootnote 6. Research undertaken to understand these associations and the distinct role of UPF is increasing.

This is an emerging and complex area of research that warrants attention given the prominent role of UPF in the diets of Canadians and the signals of association between high levels of UPF consumption and adverse health outcomes. This BBE was designed to help clarify knowledge gaps and accelerate research to increase certainty in the evidence.

Best Brains Exchange

The Best Brains Exchange explored several topics related to two main themes:

The relation between UPF consumption and health

  • Association between UPF consumption and health outcomes: state of evidence from observational studies, clinical trials, and intervention studies
  • Challenges in classifying food intake data by degree of processing. Considerations for collecting and interpreting food intake data
  • Tackling heterogeneity of UPF to understand their impact on health

Potential attributes, plausible pathways and mechanisms of UPF

  • Overview of potential pathways of effect and hypothesized mechanisms of UPF consumption and health
  • The food matrix: implications of ultra-processing and considerations for health
  • Driving consumption: characteristics of UPF that affect eating rate and overconsumption
  • How does the body respond to UPF? Biological mechanisms: current knowledge on how characteristics of UPF interact with the gut microbiota and inflammation, raising concerns for adverse health outcomes

BBE Approach

A small number of BBE participants were invited to provide brief presentations to stimulate thinking on specific topics under each theme, followed by facilitated dialogue and focused break-out groups. Key points from these discussions are outlined below.

The relation between UPF consumption and health

Association between UPF consumption and health outcomes

  • Epidemiological research shows an association between UPF consumption and several adverse health outcomes, however, using the GRADE approach, the certainty of evidence has been deemed “low” due to a lack of RCTs and concerns about the accuracy of UPF intake measurements.
  • The association between UPF consumption and health cannot be fully explained via nutrient pathways alone.
  • Considering the level of food processing independent of nutritional composition provides a complementary lens regarding dietary intake and health.
  • The results of the first RCT studying the effect of UPF exposure found that when people ate diets high in UPF food, they gained weight and body fat compared to when they ate a diet based on minimally or unprocessed foods, when matched for calorie and nutritional content.
  • While RCTs are recognized as the “gold standard” for studying causal relationships, ethical concerns, costs, and logistical challenges limit their use in studying the association between long-term exposure of UPF consumption and health outcomes – as is the case with most nutrition research.

Challenges in classifying food intake data by degree of processing, methodological considerations

  • Efforts by researchers to support consistent methodological approaches continue. Traditional dietary intake measurement tools are not designed to collect nor assess dietary intake by degree of food processing. Exposure assessment could be improved by recording details such as brands, preparation method, and location.
  • The accuracy of classifying food by level of processing is also increased when using dietary assessment tools validated for assessing UPF consumption.
  • Evidence does not support claims that UPF are routinely misclassified and/or that misclassification is biased toward over-estimating associations.
  • Sensitivity analyses in large cohort studies have shown that when adjusting for potential misclassification, the direction of risk stays the same, suggesting misclassification does not systematically increase observed associations.

Tackling heterogeneity of UPF to understand their impact on health

  • Large multi-centre cohort studies have shown that it is possible to assess consumption of UPF based on data that comes from diverse food systems and food environments, and that relates to diverse types of UPF.
  • Biomarkers can be used to validate the harmonization of heterogenous dietary intake data.
  • Heterogeneity within the UPF category can be studied by analyzing sub-groups of UPF with different characteristics.
  • Some studies have found that not all UPF subgroups (researcher assigned) were equally associated with risk of cancer-cardiometabolic multi-morbidity.

Potential attributes, plausible pathways and mechanisms of UPF

Potential pathways of effect and hypothesized mechanisms

  • Several potential pathways of effect have been identified in the literature, reflecting the impact of various properties of UPF, including lower nutritional quality, changes to the food matrix and texture, contaminants from processing and packaging, additives, industrial ingredients, and hyper-palatability.
  • Efforts to synthesize research on mechanisms are hindered by comparability issues across studies, including inconsistent definitions of a potential mechanism, UPF exposure, or outcome. Better research synthesis, specifically higher quality systematic review methods [e.g., utilizing well defined PECO statements (Population, Exposure, Comparator, and Outcomes) and evaluating homogeneous exposures], is needed to understand which attributes of UPF consistently lead to the observed negative health outcomes.
  • To support understanding of causality, more research is needed to identify specific UPF properties that lead to consistent evidence of adverse health outcomes.

Hyper-palatability of ultra-processed foods

  • Hyper-palatability is the intensified appeal of foods due to a combination of ingredients like high fat and sodium, fat and sugars, or carbohydrates and sodium.  
  • Many UPF are hyper-palatable.
  • UPF which increase the pleasure of eating through hyper-palatability may harm health by triggering over-eating and the consumption of excess calories and/or other unique attributes of UPF.

The food matrix: implications of ultra-processing and considerations for health

  • Whole foods and their ultra-processed derivatives do not have the same physical structure (food matrix), and they are not digested in the same way.
  • Combinations of isolated compounds from whole foods that are contained in UPF do not provide the same physiological responses as the original whole food.
  • Machine simulators demonstrate there are major differences in how whole foods and UPF are digested in the upper digestive system or in the intestines, suggesting possible pathways for the observed health effects of UPF.

The gut microbiota and inflammation

  • The gut microbiota can protect against pathogens and contribute to immune system balance. In some situations, however, gut microbiota can also contribute to chronic inflammation and metabolic issues. Its effect on health is not yet well understood and is being actively researched.
  • For example, one common type of UPF ingredient that affects gut microbiota is emulsifiers. Emulsifiers are food additives used to improve texture and extend shelf-life food. Some emulsifiers have been shown to cause inflammation and colitis in mice prone to colitis, but not in others. Research on humans has also linked some dietary emulsifiers to chronic and inflammatory diseases in susceptible people, similar to the effect observed in susceptible mice.

Knowledge gaps and considerations

The presentations and discussions during the breakout and open sessions raised several issues, knowledge gaps, and considerations. While the BBE did not seek consensus, nor were specific research priorities identified, some recommendations emerged as next steps.

Epidemiology

  • Improve dietary intake tools to better assess UPF consumption (e.g., improve ability to capture UPF consumption by ensuring sufficient granularity of dietary assessment tools; improve ability to classify foods by level of processing by including information on food additives in food composition databases).
  • Explore specific emerging relationships more fully, for example, the relationship between UPF consumption among those experiencing early-onset cancers.
  • The need for, and approach to, sub-categorization of UPF in research requires careful consideration and theoretical rationale (e.g., categorize according to hypothesized attribute or mechanism).

Pathways of effect and mechanisms

Participants noted that research in this area is nascent and suggested the following approaches to enhance knowledge:

  • Develop clinical trials with the highest likelihood of elucidating mechanisms for one or two health outcomes and use this experience to inform other research efforts.
  • Prioritize the pathways through which UPF contribute to over-consumption. For example, identify components of the food matrix and digestive processes which may drive overconsumption (e.g., how food matrix impacts satiety, rate of absorption, and transit time).
  • Be open to alternate ways of studying the impact of UPF on health that may differ from traditional nutrition and diet studies.
  • Leverage multi-omic methods, for example, by identifying metabolic biomarkers to establish exposure, then working backwards to examine mechanisms.
  • Use mediation analyses to clarify potential mechanisms.

Generalizability across populations

Much of the research exploring UPF consumption and health outcomes is among adult populations. Suggestions were made to broaden the evidence base to understand unique considerations for other populations and enhance generalizability, for example:

  • Utilize a life-cycle perspective to understand impacts of UPF consumption in other life stages including pregnancy, infancy, early childhood, and old age.
  • Include equity and diversity considerations in cohort study design. Inclusion of under-represented communities would provide an opportunity to understand disproportionate impact across the population.

Drivers of UPF consumption

Participants noted that broader factors that impact consumption of UPF are important to understand, for example:

  • Consider and seek a better understanding of the factors that influence increased or disproportionate consumption of UPF in the population (e.g., commercial determinants of health, cost and availability of UPF, among other drivers).
  • Complement epidemiology and mechanistic studies regarding UPF consumption and health, with social science research to have a more holistic understanding of the issue at the population level.

Research methods to strengthen evidence

The following suggestions were made for ways to increase the reliability of research on how UPF impact health:

  • Improve systematic review approaches to enhance quality of results.
  • Ensure the dosage in animal studies that is used to clarify causal pathways is appropriate for informing understanding regarding human consumption and health; use standardized research protocols to facilitate acceptance of results.
  • Support more randomized controlled trials; conduct human trials with strict control on participants’ diets in appropriate facilities (e.g., metabolic chambers or domicile facilities).
  • Accelerate knowledge development by employing a variety of methods and approaches; triangulate results to address complexities in food exposure.
  • Explore biomarkers or other new tools to validate UPF exposure.
  • Conduct formal mediation analyses to understand and clarify mechanisms.

Conclusion

Health Canada will continue to monitor the evidence. Since the Best Brains Exchange in June 2024, science on UPF and health continues to evolve and additional areas of interest continue to emerge.

Health Canada, CIHR-INMD, and CIHR-ICR are grateful to the members of the planning committee for their contributions to organizing this Best Brains Exchange, and to the speakers and participants for their willingness to share their expertise.

For more information

Learn more about CIHR’s Best Brains Exchange program

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