Junk food for thought: Landmark study directly links ultra-processed foods to poor health

Researchers at McMaster University investigated the relationship between ultra-processed food (UPF) consumption and risk factors including blood pressure, cholesterol levels (LDL and HDL), waist circumference and body mass index (BMI).

Their study is the first in Canada to leverage population-based and robust biomarker data to examine this relationship.

The team analyzed data from more than 6,000 adults across Canada, representing a diverse range of ages, health conditions and socio-economic backgrounds. The subjects completed a questionnaire for the Canadian Health Measures Survey, conducted by Health Canada and Statistics Canada, and were then personally assessed at mobile clinics.

Individuals who consumed the most UPF were more likely to be men, and to have lower income levels, less education and to have reported lower fruit and vegetable intake. They had significantly higher BMI, waist circumference, blood pressure, insulin, and triglyceride levels than those who consumed the least UPF.

Researchers noted that many links between UPF consumption and cardiometabolic risk factors remained significant even after adjusting for BMI, suggesting that ultra-processed foods may influence health through mechanisms beyond weight gain, such as inflammation, insulin resistance, and poor metabolic regulation -- all well-established predictors of heart disease and type 2 diabetes.

The associations persisted even after adjusting for physical activity, smoking, the total amount of food consumed and socioeconomic factors including income and education.

"We have this very complex food supply that is more than just the nutritional composition of a food," explains Anthea Christoforou, an assistant professor in the Department of Kinesiology at McMaster University and senior author of the paper.

"It may be about the additives. The way the food is prepared. It's related to the packaging and the marketing of that food. All these things come together to create this food environment that really affects the healthfulness of our diets."

The study, published today in the journal of Nutrition and Metabolism, uncovered a strong association between UPF consumption and the presence of C-reactive protein (CRP), which the liver produces in response to inflammation, as well as an increase of white blood cells.

"These two biomarkers indicate that these foods are causing an inflammatory response in our bodies. In a sense, this suggests that our bodies are seeing these as non-foods, as some kind of other element," says Christoforou.

UPFs are ready-to-eat, pre-packaged foods, often high in sodium, sugar and unhealthy fats, while being low in fibre, minerals and vitamins. They are often more convenient, heavily marketed, and appeal to time-pressed consumers, factors that may contribute to higher consumption among lower-income groups and growing health disparities.

Researchers point out that such foods have come to dominate the global food supply, particularly in middle- and high-income countries. Canadian study participants consumed an average of more than three servings of UPFs per day, but those who consumed the highest amounts averaged six servings daily, and researchers believe UPFs may be replacing healthier foods such as fruits and vegetables.

"Ultra-processed foods are impacting health across all socioeconomic groups," says Angelina Baric, a graduate student in the Department of Kinesiology at McMaster and co-author of the study. "While some populations are more exposed to these foods, our findings show that the health risks persist independently of income and education. This highlights the need for broad, equitable food policies that protect everyone."

Health Canada currently recommends reducing the consumption of processed foods as part of its healthy eating guidelines and has begun consultations to develop broader strategies for limiting UPFs in the Canadian food supply.

"We found consistent evidence that eating ultra-processed foods is associated with cardiometabolic risk factors, which not only reinforces the evidence we have seen linking these foods with rising overweight and obesity rates in Canada and other parts of the world, but also provides more detailed information about what's happening in the body before a full disease," says Baric.

In future, the research team plans to develop a study on children's eating habits as related to processed foods, and female health, focusing on fertility, menses and the onset of menopause.

They are also investigating the biological mechanisms by which UPFs may trigger inflammation and metabolic dysfunction and exploring the role of affordability and food environments in driving UPF consumption -- with the aim of informing more equitable public health strategies.