As research on the adverse health impacts of ultra-processed foods (UPFs) continues to expand, researchers urge national dietary guideline recommendations and public policies to advise reducing UPF consumption. The team suggests that premature deaths attributable to UPFs increase significantly for populations with higher consumption.
However, experts reacting to the study caution against interpreting its details and numerical estimates. They say more research is needed to ascertain a causal link between UPF consumption and diseases or mortality.
The study modeled data from nationally representative dietary surveys and mortality data from Australia, Brazil, Canada, Chile, Colombia, Mexico, the UK, and the US. The researchers used this data to link dietary patterns, considering the extent and purpose of industrial food processing, to deaths from all causes.
“Assessing deaths from all causes associated with UPF consumption allows an overall estimate of the effect of industrial food processing on health,” says the study’s lead investigator, Eduardo Augusto Fernandes Nilson from the Oswaldo Cruz Foundation, Brazil.
“UPFs affect health beyond the individual impact of the high content of critical nutrients (sodium, trans fats, and sugar) because of the changes in the foods during industrial processing and the use of artificial ingredients, including colorants, artificial flavors and sweeteners, emulsifiers, and many other additives and processing aids.”
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Increase in mortality risk
For the research published in the American Journal of Preventive Medicine, the team conducted a meta-analysis of observational studies to determine the link between UPF consumption and all-cause mortality. The authors estimated the effect on mortality for each 10% increase in UPF consumption.
The analysis showed that each 10% increase in UPFs in the diet increased the risk of death from all causes by 3%, says Nilson.
“Then, using the relative risks and the food consumption data for all countries (ranging from 15% of the total energy intake in Colombia to over 50% of the calories in the US), we built a model that estimated that the percentage of all-cause premature, preventable deaths due to the consumption of UPFs can vary from 4% in countries with lower UPF consumption to almost 14% in countries with the highest UPF consumption.”
Doctors walking in a hospital
Nilson says the analysis showed that each 10% increase in UPFs in the diet increased the risk of death from all causes by 3%.
“For example, in 2018, 124,000 premature deaths were attributable to the consumption of UPFs in the US.”
However, Kevin McConway, emeritus professor of Applied Statistics at the Open University, UK, says no observational study can determine whether varying UPF intake levels cause differences in mortality between people who consume different UPF amounts. McConway is not a part of the study.
Statistical calculations
Moreover, McConway spots some statistical issues in the study’s analysis. He explains that the researchers compare their estimates of additional deaths attributable to UPF consumption to a theoretical population that has never consumed UPFs. “The deaths attributable to UPF consumption are the difference between these two expected numbers of deaths.”
“What this sounds like, for the UK in 2018–19, for example, is that there would have been almost 18,000 fewer deaths of people aged between 30 and 69 if nobody in the country had consumed any UPFs,” he adds.
However, he stresses: “There isn’t a whole population in the UK or the other seven countries in the study where nobody ever consumed any UPFs. So the comparison is being made between an estimate for current UPF consumption levels and an estimate for a theoretical population that can’t exist.”
Therefore, McConway concludes that reducing UPF consumption could not save 18,000 premature deaths annually in the UK.
“This doesn’t mean that taking such actions wouldn’t reduce early deaths — just that we can’t tell how much the reduction might be, when it would occur, or how much longer the individuals concerned might have lived — not from the calculations in this paper.”
Nutritionist holding apple and donut
McConway stresses that the paper’s calculations do not prove how many premature deaths could be achieved by reducing UPF consumption.
UPF health risks
Previous research has linked higher UPF consumption to a wide range of health issues, from higher fat inside thigh muscles and diabetes to an increased risk of developing 32 adverse health outcomes, such as cancer, cardiovascular, or metabolic health issues.
With their findings, the study authors recommend national dietary guidelines should aim to reduce UPF intake.
“It is concerning that, while in high-income countries UPF consumption is already high but relatively stable for over a decade, in low- and middle-income countries the consumption has continuously increased,” says Nilson.
“While the attributable burden in high-income countries is currently higher, it is growing in other countries. This shows that policies that disincentivize the consumption of UPFs are urgently needed globally, promoting traditional dietary patterns based on local fresh and minimally processed foods.”
Nutritional profile, not processing?
There is an ongoing debate among researchers about what causes these adverse health impacts — a food’s processing level or its sugar, salt, and fat content, which tends to be higher in many UPFs. Moreover, not all UPFs have the same impact on health.
For example, US researchers unveiled a database ranking processed foods on their ingredient lists, nutrition facts, and prices earlier this year to help unlock healthier choices. Recently, we spoke to the authors of a study calling to prioritize biochemical composition and plant-based foods’ nutritional values over processing levels.
Nutritionist giving dietary advice based on nutrition facts
Instead of their processing levels, researchers link UPFs’ adverse health impacts to their high sugar, salt, and fat content.
Dr. Nerys Astbury, associate professor of Diet Obesity at the University of Oxford, UK, also believes that “rushing to add recommendations on UPF” to national dietary guidelines is not warranted based on the study’s findings.
“Many national dietary guidelines and recommendations already advise reducing consumption of energy-dense, high-fat, high-sugar foods, which typically fall into the UPF group. Adding additional recommendations based on UPF could cause consumer confusion — some foods may be considered unhealthy by nutrient standards but not by NOVA classification (and vice versa).”
“This study and other similar studies that have explored the association between UPF and diet-related disease have used the NOVA classification system invented by Dr. Carlos Monteiro (an author of this paper).”
He says that the NOVA system that classifies foods according to their processing levels has many limitations, including “arbitrary definitions and overly broad food categories, the over-emphasis of food ingredients as opposed to the processing per se, and the difficult practical application of the system in accurately classifying foods.”
“This is especially notable when attempting to classify foods from dietary data collected in large cohort studies, as in this study,” he cautions.
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