Cancer is one of the leading causes of mortality worldwide and has been linked to changes in lifestyle-associated factors such as alcohol intake, smoking habits, diet, and physical activity. One dietary factor that has recently gained attention in relation to cancer risk is ultra-processed foods (UPFs). These are dietary formulations that have undergone multiple levels of processing in industries to lower microbial deterioration, increase shelf-life, enhance transportability over long distances, and enhance palatability. UPFs contain various diet additives, including colorants, sweeteners, and emulsifiers, and are staple foods in several nations.
Studies have reported that the consumption of a Western diet high in UPF content increases the chances of developing non-communicable diseases, including cancer. However, data on the molecular mechanisms, carcinogenic properties, and characteristics of the effects of increased UPF intake on health are limited.
In a recent study, researchers investigated whether UPF consumption is linked to an elevated cancer risk. They searched databases such as EMBASE and PubMed for original research articles, including peer-reviewed and observational-type studies, on 28 March 2022 and 5 January 2023. The study assessed the relationship between UPF consumption and cancer risk among adults using the NOVA scheme as the study exposure and cancer as the study’s outcome. They conducted a random-effects-type meta-analysis, reviewed records, and evaluated the risk of bias based on the National Institute of Health (NIH)’s tools for quality assessment.
The study outcomes included cancer types such as breast, colorectal, pancreatic, prostate, central nervous system tumors, and chronic lymphocytic leukemia. They calculated hazard ratios (HR) for prospective cohort-type studies and odds ratios (OR) for case-control-type studies. Records assessed for melanoma and skin cancers of non-melanoma type using or not using multiple NOVA classifications were excluded from the analysis. In addition, meta-analyses, reviews, editorials, letters, and animal studies were excluded.
Out of the initial 265 records identified, 23 studies were published before 2009, and 65 were duplicates. After exclusions, 11 relevant records were considered for the final analysis, including three prospective cohort-type studies and eight retrospective case-control-type studies. The sample population varied across studies, ranging between 132 and 206,248 individuals, including participants of the French NutriNet-Santé study, the Nurses’ Health Study (NHS), NHS II, the Health Professionals Follow-up Study (HPFS), and the Mediterranean diet in relation to cancer of brain (MEDICEA) study.
Nine of the 11 records documented a significant positive relationship between UPF intake for all cancers investigated, except prostate cancer, after adjusting data for confounding variables, including adiposity and total caloric intake. A 10.0% increase in the dietary UPF proportion was related to elevated breast cancer risks, with HR values of 1.1 and breast cancer, respectively. Additionally, increased UPF consumption was related to an elevated risk of pancreatic tumors (HRQ4 versus Q1, 1.5) and colorectal tumors (ORT3 versus T1, 1.3). The relationships between UPF intake and the risk of developing chronic lymphocytic leukemia and central nervous system tumors were modest.
In the meta-analysis, pooling the findings for cancer outcomes indicated that UPF consumption was significantly related to cancer for prospective cohort-type studies (HR 1.1) and those of case-control type (OR 1.2). Diet records were largely obtained using food frequency questionnaires, online 24-hour diet recalls, and diet history questionnaires (DHQ). UPF items contributing to the association include sugary foods and beverages, ready-to-eat foods, bread, cakes,