Researchers warn against criminalizing the entire food group

Food scientists suggest that lifestyle factors may be more responsible for negative health effects than eating ultra-processed foods, challenging current public health recommendations.

Perspective: Ultra-processed foods and health: are we interpreting the available evidence correctly? Image credit: Rimma Bondarenko / Shutterstock

In a recent insight piece published in European Journal of Clinical Nutritionresearchers discussed epidemiological studies on the effects of ultra-processed food (UPF) consumption on human health.

They conclude that there is insufficient evidence that ultraprocessing specifically, and not other confounding factors, causes the observed adverse results.

Confounding factors and proxy behaviors

Several recent studies have found associations between UPF consumption and negative health effects, including increased risks of obesity, overweight, heart disease, type 2 diabetes, and cancer. The researchers also found that people who consume the highest amount of UPF may be at a higher risk of all-cause mortality.

Results of studies showing correlations between UPF consumption and poor health have often been interpreted causally, meaning that UPF consumption causes poor health outcomes. However, the studies are primarily observational, so causality cannot be inferred and confounding factors may play a role.

In these studies, researchers must also assume that dietary intake measurements are accurate and precise, that food composition is known and can be quantitatively characterized, and that results are not affected by food storage, cooking, and preparation. food.

A step in the right direction is a recent study that focused on the contribution of emulsifiers, finding that some (but not all) were linked to the likelihood of developing some types of cancer and overall cancer risk. However, the researchers caution that extending these findings to all emulsifiers is incorrect, as many have not been associated with cancer risk.

The importance of subgroup analyses

One problem is that studies may combine different UPF groups into a single category and that many published papers do not explicitly mention subgroup analyses. However, even within a single study, different subgroups may show significantly different relationships with health outcomes.

For example, while some UPFs (including sauces, margarine, and foods containing ultra-processed fats) may be associated with a higher risk of diabetes, cancer, or heart disease, there is evidence that others, such as ultra-processed grains or bread. , can be protective.

Another study found that the relationship between heart disease and UPF consumption is driven by increased consumption of sauces, condiments and ultra-processed fats and lower fiber intake. An analysis of the link between colorectal cancer death and UPF consumption found that it was attributed to consumption of ultra-processed ice cream and sherbet.

Similarly, a study linking mortality to UPF consumption found that most of this relationship came from ultra-processed beverages. While the incidence of breast cancer has been linked to sugary products, it is not associated with sweetened beverages. No studies to date have found associations between negative health effects and ultra-processed vegetables or fruits. The lack of subgroup analyzes in many studies means that some UPFs may be unfairly grouped with those that pose more significant health risks, further complicating public health messages.

Regional differences and UPF consumption

Thus, experts say that while people who consume the highest amount of UPFs may face the most overall health risks, this may be attributable to a small set of UPFs rather than ultra-processing itself. For example, certain animal-based products were determined to be unhealthy long before the current UPF classification was introduced.

The observed relationships may be because UPF consumption is often a proxy for suboptimal lifestyles or diets. That is, people with poorer diets are also more likely to engage in unhealthy habits such as smoking.

Importantly, the results also show significant regional heterogeneity. On average, people in Italy consume less UPFs; there, all-cause mortality increases significantly for people whose UPF consumption contributes about 24% of their energy intake.

Findings in countries where people consume more UPF, such as the UK, are different. Mortality increases only after UPF consumption increases to more than 40% of total energy consumption. This regional variation suggests that other factors, such as lifestyle and dietary patterns, may play a greater role than UPF consumption itself.

Notably, the studies found no increased mortality risk associated with UPF consumption among low-income US populations who were highly dependent on ultra-processed items. As UPFs in some countries are unlikely to be healthier than others, this further supports the idea that confounding factors such as wider dietary habits or socio-economic status may account for the observed differences.

ConCluSIonS

Consolidating the current evidence requires presenting results for all UPF groups and not combining them into a single category. Studies must also investigate each step of the food preparation process and the specific compounds that might contribute to observed negative health outcomes.

If ultra-processing is not the culprit causing poor health outcomes, then public health recommendations aimed at limiting UPF consumption will not improve health outcomes. In turn, it could reduce access to nutrition for low-income populations that depend on these products.

The observational evidence from the current studies can be strengthened by using experimental frameworks that explore the mechanistic and causal bases of these relationships. More experimental research is needed to directly investigate causality between UPF consumption and health outcomes, which observational studies cannot establish. Consideration should also be given to UPFs that may be “nutritionally beneficial” and protective against some disease or negative health outcomes.