A 2019 extension of the French NutriNet-Santé observational study published in the JAMA Internal Medicine indicated the consumption of ultra-processed foods was associated with an increased risk of early mortality among adults. The study participants consumed a reasonable composite nutrient profile, while the investigators noted these foods actually contributed lower levels of calcium, B-vitamins, and complex carbohydrates, just to identify a few. The classic use of Cox proportional hazards regression indicated a 95 percent confidence interval of 1.04 to 1.32. However, the authors noted a limitation that the included population mortality rates were probably lower than those of the study participants, and possibly this variable may underestimate the association.
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Reflecting on this study, it remains somewhat arbitrary to define foods that have > 5 ingredients as ultra-processed. Food ingredients and food additives are safe and provide function and stability to those products. While the authors mention these variables, the study does not provide any data on the quantitative consumption of food additives, but only speculates on their association with longevity. It is interesting that, for example, homemade or artisanal bread is not considered ultra-processed, whereas the same product produced by the food industry using the same ingredients is considered ultra-processed.
A closer examination of this study certainly reveals that perhaps lifestyle, living alone, smoking, obesity, and low levels of physical activity are contributing factors to mortality rates. In addition, a review of the survey instrument calls into question of validity and even calculation of nutritional intake. Importantly, the study cannot establish that ultra-processed foods cause an increase in the short-term risk of death, especially since the differences in death rates between consumers and non-consumers of ultra-processed foods were small—in fact, the authors state, “No causality can be established for the observed associations.”
A number of epidemiological studies suggest the consumption of ultra-processed foods contributes to excess calorie consumption and obesity. These kinds of studies from Sweden (1960-2010), the U.S (2005-2014), Brazil (2008-2009), Mexico (2012), and Europe (data from Living Costs and Food Survey and Data Food Networking 1991-2009) indicated an association with the consumption of ultra-processed foods and the increased risk of obesity and other non-communicable diseases. However, the association indicated by R2 value ranged from 0.30 to 0.63, depending on adjustments for variables such as smoking and physical activity. Within the U.S., a 2017 study suggested these foods were associated with obesity and adverse cardiometabolic outcomes in the absence of any statistical justification.
The Necessity of Processing
It is important to point out that epidemiological studies do not directly indicate a causal impact. As a famous toxicologist once said, “Mathematics does not drive biology; biology drives mathematics.” Statistical association without a plausible biological explanation or hypothesis is likely to represent little more than a spurious connection.
Moreover, one can argue that no single attribute of food processing contributes to an increase or decrease risk of a given chronic disease. Foods represent complex matrices with multiple nutrients and physical characteristics. For example, whole grain consumption may reduce the risk of hypertension and visceral adiposity. However, grains must be processed so that their nutritional contributions may be realized.
The NOVA classification of foods and its purported impact on more healthful dietary patterns is being considered a key justification within dietary guidelines recommendations. The concept of “ultra-processed” foods has morphed considerably since 2009. Food products continue to be reformulated across food categories such that those foods are components of dietary patterns consistent with those recommendations. Even with these efforts, it is critical to remember that all forms of processed foods are important components of the food supply chain. In fact, they reduce food insecurity issues, provide sources of vital nutrition, contribute to consumer choices, and even stimulate regulatory guidance in food composition and health claims.