The study, which was presented at a nutrition conference in Chicago yesterday (30 June 2024), drew data from more than 540,000 US adults over the course of almost three decades.
How was the study conducted?
The participants provided information about their eating habits and health in the mid-1990s, when they were between 50 and 71 years of age. Over half of the participants have since died.
The researchers looked at the overall death rates among those in the 90th percentile for UPFs consumption versus those in the 10th, alongside analysing whether there were any associations with specific diseases or food.
The results found that a higher intake of ultra-processed foods was associated with modest increases in death from any cause and from deaths related specifically to heart disease or diabetes. No association was found with cancer-related deaths.
“We observed that highly processed meat and soft drinks were a couple of the subgroups of ultra-processed food most strongly associated with mortality risk and eating a diet low in these foods is already recommended for disease prevention and health promotion,” explained said Erikka Loftfield, PhD, Stadtman investigator at the National Cancer Institute.
There is no universally agreed definition of processed foods and a number of classification systems have been developed globally, which attempt to group foods by their level of processing. For this study, the researchers classified the level of processing by breaking down food frequency questionnaire data into particular food and ingredient types, as well as incorporating expert consensus to categorise dietary components in line with the NOVA system.
According to this study, people who consumed UPFs tended to also have a higher body mass index and a lower Healthy Eating Index score (a measure of diet quality based on how closely a person’s diet aligns with the Dietary Guidelines for Americans).
While the researchers also took into account factors such as obesity and smoking, the team said the findings showed that mortality risk persisted in those who were also identified as 'normal' in weight.
'Still a lot we don't know'
It is worth noting that the study design did not allow researchers to determine causality. In addition, Loftfield noted that the US food supply and dietary preferences have changed considerably since the study’s baseline data was collected in the mid-1990s, underscoring the importance of continued research to further elucidate the relationships between food processing and human health.
Moreover, although the abstracts presented at NUTRITION 2024 were evaluated and selected by a committee of experts, they have not generally undergone the same peer review process required for publication in a scientific journal.
“Our study results support a larger body of literature, including both observational and experimental studies, which indicate that ultra-processed food intake adversely impacts health and longevity,” added Loftfield. “However, there is still a lot that we don’t know, including what aspects of ultra-processed foods pose potential health risks.”
UPFs in the UK
This study is the latest in a long line of research emerging around UPFs. In the UK, the Scientific Advisory Committee on Nutrition (SACN) reviewed the evidence on processed foods and health in 2023; it concluded that because of limitations to the research available caution is still needed when it comes to making dietary recommendations.
UPFs were also the topic at Food Manufacture's most recent Business Leaders' Forum, with leaders contenting that the ultra processed food conversation has been "hijacked by the national media".
