WHILE ULTRA-PROCESSED food (UPF) is the latest buzzword in nutrition, scientific evidence on its health effects points in different directions. Why can’t researchers tell us the perfect diet?
Shifting Nutrition Advice
The evolution of nutrition advice is a complex journey. In the 1990s, fats were blamed for rising obesity rates. Then, in the early 2000s, carbohydrates took the spotlight. The consensus is to opt for whole foods and steer clear of ultra-processed ones. However, this shift doesn’t guarantee a healthier diet. The mixed results from studies on UPF, as highlighted at a recent meeting of the American Society for Nutrition in Chicago, underscore the intricate nature of nutrition advice.
Mixed Research Findings
At the meeting, researchers presented conflicting findings on UPF’s health impacts. For instance, one study showed that people who consume more UPF had a greater risk of dying during the study period than those who ate less UPF. This conclusion was drawn from analysing data from over 500,000 people in the US. Participants who enrolled in the study between 1995 and 1996 filled out a food frequency questionnaire and were followed up two decades later. The study found that those who ate the most UPF had a roughly 10% greater chance of dying during this period, even after accounting for diet quality and body mass index.
While this suggests UPF increases the risk of dying early, other factors could explain the association. People who cook from scratch may also prioritise exercise or sleep, which might be the underlying factors rather than UPF. Most studies on UPF are observational, making it difficult to untangle these effects. Additionally, dietary preferences have changed significantly over the past 30 years, complicating long-term studies. For instance, the average person in the US now consumes more chicken and cheese and less beef and potatoes than in the 1990s.
Defining Ultra-Processed Foods
Even avoiding UPF does not guarantee health. There needs to be a universal definition of what makes a food ultra-processed. Most studies refer to the NOVA food classification system, developed by Carlos Monteiro at the University of São Paulo, Brazil. This system categorises foods based on the extent and purpose of their processing. According to this system, UPF includes foods made entirely from ingredients extracted from foods or synthesised in laboratories. It includes store-bought cookies, soft drinks, sweets, and wholewheat breakfast cereals and is a good source of fibre, iron, and other micronutrients.
Allen Levine at the University of Minnesota says, “You can’t automatically dismiss ultra-processed foods as bad or unhealthy and automatically assume that non-processed foods are healthy.” Levine’s research demonstrated this by constructing two seven-day menus of similar meals. UPF constituted 67% of the calories in one menu and 20% in the other. Despite this, according to the Healthy Eating Index, both menus provided low-quality diets, scoring 44 and 43 out of 100, respectively. This suggests that the issue is about more than just the processing of the food but also about the overall nutritional quality of the diet.
The Real Culprit: Processing or Nutrient Content?
It raises the question of whether UPF is linked to poorer health outcomes because it is processed or higher in fats, sugars, and salt. “If you match [UPF] to a non-processed [food] using the same set of macronutrients – protein, fat, carbohydrate – why would one be different than the other?” asks Levine. “Some people think, ‘Oh, it’s the food additives,’ but I don’t see a lot of evidence for that.” Individual differences in response to these foods could also play a role. Until this question is answered, we can’t say for sure that UPF is terrible for our health.
The Cost and Practicality of UPF
Vilifying UPF risks dismissing foods, many people rely on for quick, easy, and low-cost meals. Levine’s research found that the UPF-heavy menu costs about £10 less per day than the one with fewer UPF while providing comparable nutrients. Another study by Julie Hess at the US Department of Agriculture constructed a seven-day menu with a diet quality score of 86, despite 91% of the calories coming from UPF.
Conclusion
What we should eat to stay healthy is an ongoing debate. As Levine puts it, “Food is a complicated structure. Everybody thinks it’s simple. It’s not.” As long as research presents mixed findings, the debate over UPF and its health implications will continue, inviting us all to be part of the discussion.
