Eating ultra-processed food raises the risk of cancers in the upper aerodigestive tract, including mouth, throat and esophagus, a new study has found. Researchers note that the correlation is not solely due to obesity.

A team, led by researchers from the University of Bristol and the International Agency for Research on Cancer (IARC), analyzed the link between head, neck and esophageal cancer and consumption of ultra-processed food. They analyzed the diet and lifestyle data of 450,111 adults who were followed up for around 14 years. The results were published in the European Journal of Nutrition.

Ultra-processed food is manufactured using industrial formulations, with ingredients and additives such as emulsifiers, flavoring agents and artificial sweeteners generally not used in normal cooking in kitchens. Soft drinks, packaged snacks, confectionery, packaged breads and buns are some examples.

Studies have shown that ultra-processed food items can be as addictive as nicotine or alcohol. The use of certain types of additives such as emulsifier E in ultra-processed food has been linked to an elevated risk of cardiovascular disease.

"UPFs (ultra-processed food) have been associated with excess weight and increased body fat in several observational studies. This makes sense, as they are generally tasty, convenient, and cheap, favoring the consumption of large portions and an excessive number of calories. However, it was interesting that in our study the link between eating UPFs and upper-aerodigestive tract cancer didn't seem to be greatly explained by body mass index and waist-to-hip ratio," the study's lead author, Fernanda Morales-Berstein, said in a news release.

The analysis showed that eating 10% more UPFs raised the risk of head and neck cancer (HNC) by 23% and the risk of esophageal adenocarcinoma (OAC) by 24%.

"In this large prospective cohort, UPF consumption was associated with an increased risk of HNC and OAC. The positive association between UPF intake and HNC may be stronger in males than in females," the researchers wrote.

The study indicated that only a small proportion of the positive association was contributed by obesity, measured as adiposity in terms of BMI and weight-to-hip ratio.

Other factors responsible for elevating risk include the use of additives such as emulsifiers and artificial sweeteners in ultra-processed food, which were previously linked to cancer. Contaminants in the packaging and manufacturing process could also contribute to the risk, the researchers suggest.

However, researchers warn that the associations they found between ultra-processed food and cancer risk may not be causal and could be affected by certain types of bias. For example, the study found a link between high UPF consumption and increased risk of accidental deaths, a connection that is unlikely to be causal.

"UPFs are clearly associated with many adverse health outcomes, yet whether they actually cause these, or whether underlying factors such as general health-related behaviors and socioeconomic position are responsible for the link, is still unclear, as the association with accidental deaths draws attention to," George Davey Smith, a co-author on the paper, said.

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