Ultra-processed food update: New research suggests diet quality mitigates higher mortality risk

13 May 2024 --- Higher consumption of most ultra-processed foods (UPFs) is linked to a “slightly higher” risk of death, according to a 30+-year US study. The researchers found the strongest association for ready-to-eat meat, poultry and seafood-based products, sugary drinks, dairy-based desserts and highly processed breakfast foods. Moreover, a higher diet quality seems to mitigate these associated risks.

The team cautions not to restrict all UPFs equally, noting that their findings “provide support for limiting consumption of certain types of UPFs for long-term health.” 

Over the follow-up period, researchers found that participants in the highest quarter of UPF consumption (around seven servings daily) had a 4% higher risk of total deaths, a 9% higher risk of other deaths and an 8% higher risk of neurodegenerative deaths, than people in the lowest quarter (around three UPF servings daily). 

“Overall, the research is useful and helpful being from two large, longitudinal populations in the UK and the US, and it highlights the challenges and confusion with demonizing all UPFs,” comments Dr. Aisling Daly, lecturer in nutrition at Oxford Brookes University, UK.

“However, we ultimately need a more useful system for classifying ‘healthy’ and ‘unhealthy’ UPFs to help the public make health-promoting dietary choices to improve their overall diet quality and subsequent health risks.”

Study set up 
Researchers tracked the health of 74,563 female registered nurses in the Nurses’ Health Study (1984–2018) and 39,501 male health professionals in the Health Professionals Follow-up Study (1986–2018), none of whom had a history of cancer, cardiovascular diseases or diabetes at enrolment. 

Participants provided health and lifestyle habit information every two years and completed a detailed food questionnaire every four years. The study assessed overall dietary quality with the Alternative Healthy Eating Index-2010 score. 

UPFs with the strongest mortality risks included processed meat and seafood, sugary drinks, dairy desserts and breakfast foods.The rate of death from any cause among participants in the lowest and highest quarter of UPF consumption was 1,472 and 1,536 per 100,000 person-years, respectively. 

The research, published in BMJ, found no associations for deaths due to cardiovascular diseases, cancer or respiratory diseases. 

As this study is observational, no firm conclusions can be drawn on cause and effect. Moreover, the authors point out that there may be potential misclassification of UPFs as the products’ classification system does not capture the full complexity of food processing. The generalizability of the study’s findings is also limited as the participants were predominately white health professionals. 

At the same time, the researchers underscore that the large-scale study had an extended follow-up with detailed, validated and repeated measurements. Further analyses resulted in similar results, providing confidence in its conclusions. 

Diet quality  
UPFs with the strongest associations with mortality outcomes were meat, poultry and seafood-based ready-to-eat products, such as processed meat, at a 6%–43% higher risk. Sugar- and artificially-sweetened beverages had an added average risk of 9%, dairy-based desserts were linked to a 7% higher risk and UPF breakfast foods 4% on average. 

The associations were less pronounced when the researchers included overall dietary quality in their analysis. This may suggest that dietary quality more substantially influences long-term health than UPF consumption. 

Dr. Duane Mellor, dietitian and spokesperson for the British Dietetic Association, notes that the study seems to suggest that “the risk of an early death that could be associated with the consumption of UPFs seemed not to be the case in those who consumed an overall healthy diet.” 

“It is also noticeable that those who consumed the most UPFs tended to eat few vegetables, fruit, legumes and wholegrain. This appeared to suggest that it might not be as simple as that those who ate more UPFs were more likely to die earlier — these foods might displace healthier foods from the diet.”

Mortality risks associated with UPFs were mitigated for people who consumed an overall healthy diet.In addition, Mellor comments that the study suggests that UPF classification groups foods known to be less healthy with those that may be associated with better health, such as processed wholegrain. 

“Therefore, this paper potentially challenges the view that the simple NOVA classification of ultra-processed foods into four groups (minimally/unprocessed foods, processed ingredients, processed foods and ultra-processed foods) is too simplistic and does not fully explain the health effects associated with foods.”

Healthy UPFs?  
Earlier this year, the EIT Food Consumer Observatory found that consumers are uncertain about what classifies as a UPF and how it affects health. The institute called for improved labels and education to address this confusion. 

Daly adds that while many foods are processed and some even ultra-processed, “that does not mean they are all ‘unhealthy.’”

“Many people rely on UPFs as they are affordable sources of nutrition, and UPFs are also less risky in food safety and have longer shelf lives. Equally, the process of fortifying or adding nutrients like vitamins and minerals to food can often push it into the UPF category, and you will rarely find someone claiming nutrient-enriched foods are ‘unhealthy.’”

“Demonizing all UPFs can potentially cause almost as much harm as the foods themselves if people fear them and cut them out but then can’t replace them with suitable foods. As this research rightly notes, overall diet quality is more important than UPFs’ consumption.”

Daly notes that overconsumption of UPFs high in saturated fat, sugar and salt should be discouraged due to their known negative impacts on health. Moreover, many UPFs often contain lower fiber and protein content. 

“Therefore, it is not only the fact that a food is classified as a UPF, but rather the components and quality of the UPF are important, as noted by the authors when they found that diet quality played an interacting or mediating role in their analysis,” she concludes. 

By Jolanda van Hal