The study performed by the researchers from the US, Brazil, and Canada, analyzed the association between the consumption of ultra-processed foods and increased risk of colorectal cancer.
Colorectal cancer is the third most frequently diagnosed cancer among both genders in the US and the second leading cause of cancer death in the world. The previous data indicate that ultra-processed foods (industrial ready-to-eat or ready-to-heat formulations made with little or no whole foods) now contribute 57% of total daily calories consumed by adults in the USA.
About the study
The investigation involved 3 large prospective cohorts with almost 30 years of follow-up. The Nurses’ Health Study included 121 700 registered female nurses aged 30 to 55 years at baseline in 1976. The Nurses’ Health Study II enrolled 116 429 female nurses aged 25 to 42 years at baseline in 1989, and the Health Professionals Follow-up Study enrolled 51 529 male health professionals aged 40 to 75 years at baseline in 1986.
Initially and every two years thereafter, study participants were mailed a questionnaire collecting information about demographics, lifestyle, and health problems. The average follow-up rate was higher than 90% for all three cohorts. During the 24 to 28 years of follow-up, the authors identified 3216 cases of colorectal cancer (men, n=1294; women, n=1922).
The results showed a positive association between the consumption of ultra-processed foods and the risk of colorectal cancer among men. The association was limited to distal colon cancer. These associations remained significant after further adjustment for body mass index or indicators of nutritional quality of the diet. No association was observed between the overall consumption of ultra-processed foods and the risk of colorectal cancer in women.
Among subgroups of ultra-processed foods, the results showed a positive association between colorectal cancer and higher consumption of ready-to-eat products made of meat, poultry and seafood. Ready-to-eat products made of meat, poultry and seafood included bacon, beef and pork hot dogs, chicken and turkey hot dogs, salami, bologna, processed meat sandwiches, processed meats, sausages, and breaded fish cakes/pieces/sticks. In addition, a positive association between colorectal cancer and higher consumption of sugar-sweetened beverages among men has been found.
The results also demonstrated a positive association between colorectal cancer and higher consumption of ready-to-eat/heat mixed dishes among women. Ready-to-eat/heat-mixed dishes included pizza, chowder or cream soup, soup made with bouillon, ready made soup from cans, and French fries. By contrast, a negative association has been found in women between colorectal cancer and yogurt and dairy-based desserts.
Ultraprocessed bread and breakfast foods included breakfast bars, cold breakfast cereals, English muffins, bagels, rolls, rye, white bread, and whole grain bread. Packaged sweet snacks and desserts included readymade brownies, cakes, cookies, doughnuts, pies, muffins or biscuits, sweet rolls, coffee cake, candy bars, chocolate bars, energy bars, high protein and low carbohydrate candy bars, apple sauce, jams, jellies, preserves, and honey.
Fats, condiments, and sauces included ketchup, red chili sauce, dressings, mayonnaise (regular and low-fat), salsa, margarine, butter spread, soy sauce, non-dairy coffee whitener, and cream cheese. Sugar or artificially sweetened beverages included caffeine-free Coke, Coke/Pepsi/Cola, dairy coffee drinks, Hawaiian punch, low-calorie soda, caffeine-free low-calorie soda, Pepsi, 7-up, other carbonated beverages, and other low-calorie Cola with caffeine. Packaged savory snacks included regular crackers, light fat-free crackers, and fat-free popcorn. Other ultraprocessed foods included Nutrasweet or equivalent, other artificial sweeteners, and Splenda.
The scientists noted that ultra-processed food was associated with risk of distal colon cancer independently of different dietary indices, including the western dietary pattern score, the Alternative Healthy Eating Index-2010 score, and specific food groups and nutrients that have been associated with colorectal cancer risk. It appears that other attributes of ultra-processed foods beyond food quality can be implicated in colorectal carcinogenesis.
Ultraprocessed foods usually contain food additives such as emulsifiers and artificial sweeteners, which can change the gut microbiota, promoting inflammation and carcinogenesis in the colon. In addition to additives, newly formed contaminants with carcinogenic potential (for example, acrylamide) are found in various ultraprocessed products that have undergone heat treatment, in particular French fries. Ultraprocessed foods may also contain contaminants that migrate from plastic packaging, such as bisphenol-A, which the European Chemicals Agency considers to be “a substance of serious concern.”
At the end of the study, the authors discussed the role of diet on risk of colorectal cancer at specific anatomic subsites. They also analyzed differing gender pattern. The authors concluded that their findings confirmed that limitation of certain types of ultra-processed foods is important for public health.
The study findings were published in the scientific journal British Medical Journal. Wang L. Et al. Association of ultra-processed food consumption with colorectal cancer risk among men and women: results from three prospective US cohort studies. BMJ 2022;378:e068921. (Open-Access) http://dx.doi.org/10.1136/bmj-2021-068921