A large study has found that eating more ultra-processed foods is linked to the risk of head, neck and esophageal cancer. However, they found that obesity, which is often caused by eating too much of these foods, was not the main causative factor. The findings highlight the need to examine factors other than body fat to explain this association.
Ultra-processed foods (UPFs) tend to be high in energy but low in nutrients. They often include additives and ingredients not typically used in home cooking, such as preservatives, emulsifiers, sweeteners, and artificial colors and flavors. Examples include ice cream, ham, sausages, sweets, breakfast cereals, biscuits and carbonated drinks. Consumption of UFP is associated with an increased risk of obesity.
A new study led by the University of Bristol examines the relationship between UFP intake and the risk of head, neck and oesophageal cancer, and whether obesity is a contributing factor.
Fernanda Morales-Bernstein, first and corresponding author of the study, said: "UPFs have been associated with being overweight and gaining body fat in multiple observational studies. This makes sense because they are generally tasty, convenient, and cheap, and are good for consuming large amounts of calories. Interestingly, however, the link between eating UFPs and upper gastrointestinal cancers in our study did not appear to be explained by body mass index and waist-to-hip ratio."
A study published earlier this year found that consuming more UPFs was positively associated with the risk of head and neck cancer and esophageal adenocarcinoma (a type of cancer that starts in the mucus-secreting glands of the esophagus). The researchers of this study hope to explore these findings further.
They included 450,111 participants who had participated in a previous study, the European Prospective Investigation into Cancer and Nutrition (EPIC). The study recruited participants from 10 European countries and followed them for nearly 14 years; most participants were between 35 and 69 years old at the time of recruitment, and 70.8% were female.
The foods that participants consumed that exceeded the standard mainly included carbonated drinks, non-carbonated sweet drinks, processed dairy products that exceeded the standard, processed bread that exceeded the standard, and processed meat that exceeded the standard. During the study, there were 910 cases of head and neck cancer and 215 cases of esophageal adenocarcinoma.
The analysis showed that eating 10% more UPF was associated with a 23% increased risk of head and neck cancer and a 24% increased risk of esophageal adenocarcinoma. Increased body fat explains only a small part of the statistical association between UPF consumption and the risk of these so-called upper gastrointestinal cancers.
Based on findings related to increased body fat, other mechanisms may be involved. Examples include the addition of emulsifiers and artificial sweeteners, which have been linked to an increased risk of disease, as well as contaminants in food packaging and production processes.
The researchers cautioned that their findings may be affected by certain biases. Most notably, they found a strange link between increased UPF consumption and an increased risk of accidental death.
George David-Smith, one of the study's co-authors, said: "UPFs are clearly associated with a number of adverse health outcomes, but it is unclear whether they actually cause these outcomes, or whether underlying factors such as general health-related behaviors and socioeconomic status are responsible for the link. It is the association with unexpected deaths that has raised concerns."
However, based on the finding that body fat does not largely explain the association between UPFs and cancer, the researchers recommend shifting the focus away from being overweight or obese.
"Focusing solely on weight loss treatments, such as semaglutide, is unlikely to do much to prevent upper gastrointestinal cancers associated with the consumption of UFPs," Morales-Bernstein said.
Given the age of the EPIC study, further research is needed to identify mechanisms other than body fat that may contribute to the cancer risks found in the study and to replicate the findings.
Another co-author, Inge Huybrechts, said: "Cohorts with long-term dietary follow-up assessments, taking into account contemporary consumption habits, are needed to replicate these findings, as dietary data from EPIC were collected in the 1990s, when consumption of UPFs was relatively low. Therefore, the association may be stronger in cohorts that include more recent dietary follow-up assessments."
The study was published in the European Journal of Nutrition.