A new study led by researchers at the University of Bristol and the International Agency for Research on Cancer (IARC) suggests that eating more ultra-processed foods (UPF) may be linked to a higher risk of cancers of the upper aerodigestive tract, which includes the mouth, throat and esophagus. The international study analyzed dietary and lifestyle data from 450,111 adults, following them for approximately 14 years. Researchers say obesity linked to UPF intake may not be the only cause. On November 22, relevant research results were published in the European Journal of Nutrition.
Several studies have established an association between UPF intake and cancer, including a recent study that looked at associations between UPF and 34 different cancers in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort, Europe's largest cohort study.
As evidence mounts of a link between UPF intake and adverse health outcomes, researchers from the University of Bristol School of Medicine and IARC hope to investigate this further.
Because many UPFs have unhealthy nutritional profiles, the researchers sought to determine whether the association between UPF intake and head and neck cancer and esophageal adenocarcinoma (a type of esophageal cancer) in EPIC could be explained by increased body fat.
The analysis showed that in EPIC, eating 10% more UPF was associated with a 23% risk of head and neck cancer and a 24% risk of esophageal adenocarcinoma. Increased body fat only partially explains the statistical association between UPF intake and the risk of these upper aerodigestive tract cancers.
Lead author Fernanda Morales-Berstein, a PhD student at the University of Bristol, explains: "UPFs have been associated with being overweight and gaining body fat in several observational studies. This makes sense as they are generally tasty, convenient and cheap, often consumed in large quantities and add excess calories. Interestingly, however, in our study, the link between UPF intake and upper aerodigestive tract cancers did not appear to be well explained by body mass index and waist-to-hip ratio."
The authors believe that other mechanisms may explain this association. For example, additives including emulsifiers and artificial sweeteners, as well as contaminants in food packaging and production processes, may partially explain the link between UPF intake and upper aerodigestive tract cancers in the study.
However, Morales-Berstein and colleagues expressed caution about their findings and suggested that the relationship found between UPF intake and upper aerodigestive tract cancers may be affected by some type of bias.
This explains why they found evidence of an association between increased UPF intake and an increased risk of accidental death, which is extremely unlikely to be causal.
George Davey Smith, professor of clinical epidemiology at the University of Bristol and one of the paper's authors, said: "UPF intake is clearly associated with a number of adverse health outcomes, but whether they actually cause these adverse health outcomes, or whether underlying factors such as general health-related behaviors and socio-economic status are involved in this link, is unclear because the association with unexpected deaths has attracted attention."
Inge Huybrechts, leader of the Lifestyle Exposures and Interventions Group at IARC, added: "Cohorts with long-term dietary follow-up intake assessments, taking into account contemporary consumption habits, are needed to replicate these findings, as the EPIC dietary data were collected in the 1990s, when UPF intake was still relatively low. The association may be more pronounced in cohorts that include more recent dietary follow-up assessments." Further research is needed to identify other mechanisms, such as food additives and contaminants, that may explain the observed associations.
Helen Croker, Assistant Director of Research and Policy at the World Cancer Research Fund, said: "This study adds to the growing body of evidence linking UPF to cancer risk. The association between increased UPF intake and an increased risk of upper aerodigestive tract cancers supports our cancer prevention recommendations to eat a healthy diet high in whole grains, vegetables, fruits and legumes."