A team of French and Brazilian researchers found a 10% increase in the consumption of “ultra-processed foods,” such as packaged baked goods, snacks, sugary cereals and ready meals, was associated with a 12% increased risk of overall cancer and 11% risk of breast cancer compared to diets based primarily on fresh or minimally processed foods, such as fruits, vegetables, pulses and pasta.
While the findings are significant, no firm conclusions can be drawn because they are based on an observational study of nearly 105,000 healthy French adults who completed two 24-hour online dietary questionnaires and a review of their health records.
The researchers note several hypotheses could explain their findings, including the observation that diets high in ultra-processed foods also have “generally poorer nutritional quality,” in that they tend to be higher in energy, sodium, fat and sugar and lower in fiber and beneficial nutrients. This is related to obesity which is a major risk factor in some types of cancer, they note.
Alternatively, the association could be attributed to the wide range of additives in ultra-processed foods or migration of bisphenol A from plastic packaging or even the formation of neoformed contaminants due to processing techniques, such as the development of acrylamide due to high heat, the researchers note.
Given the wide range of these possibilities, as well as the significance of their impact on health outcomes, the researchers note that additional research is necessary to better understand the relative effect of nutritional composition, food additives, contact materials and neoformed contaminants.
Even with the study’s limitations, the researchers argue as a ‘precautionary” measure, “policy actions targeting product reformulation, taxation, and marketing restrictions on ultra-processed products and promotion of fresh or minimally processed foods may contribute to primary cancer prevention.”
“A long way from understanding the full implications”
Public health experts, however, urge caution before acting on the findings.
While this research “should be commended” and raises “interesting results,” the study is only the start and replication and further refinement are necessary before firm conclusions can be drawn, caution Martin Lajous and Adriana Monge from the National Institute of Public Health in Mexico argue in an accompanying editorial.
“We are a long way from understanding the full implications of food processing for health and wellbeing,” and as such “care should be taken to transmit the strengths and limitations of this latest analysis to the general public and to increase the public’s understanding of the complexity associated with nutritional research in free living populations,” they write.
For example, they note, the study broadly defines “ultra-processed foods” to include products that are prepared in variety of ways and include myriad ingredients. As such, the study fails to identify an actual mechanism of action and result, they say.
“Is the exposure causing the disease a specific food group (such as sugary products)? Or is it a macronutrient (such as fat)? Is it a food contaminant from packaging? What are the potential carcinogenic mechanisms driving the observed association?” they ask, acknowledging, “the new study was able to explore some but not all of these important questions.”
Based on these and other limits noted by the researchers, Lajous and Monge suggest “more basic science, including data from animals,” is necessary to inform “the effect of food processing on humans.”