Many large studies conducted over long periods of time have shown that eating a diet high in ultra-processed foods increases the risk of obesity, type 2 diabetes, hypertension, cardiovascular disease, depression, and premature death.
Most of these highly processed foods, for example, soft drinks, packaged sweet and salty snacks, margarine, mass-produced breads, instant noodles, sausages, hot dogs, pre-cooked or ready-to-heat meals, ice cream, cookies, cakes, pies. mixes, sweetened yogurts: These are high in calories, unhealthy fats, added sugars and sodium, while being low in fiber, vitamins and minerals.
Now, a study published on August 31 in The BMJ has linked a high intake of ultra-processed foods to an increased risk of colorectal cancer in men. The results also suggest that attributes of these foods, beyond poor nutrient quality, are responsible for their harmful effects.
Minimally processed, processed and ultra-processed foods
The NOVA food classification system classifies all foods into four groups according to the extent of their processing. Group 1 includes “unprocessed [natural] and minimally processed foods,” which are natural foods altered by processes such as drying, grinding, filtering, roasting, fermentation, pasteurization, and freezing.
Group 2 foods are “processed culinary ingredients” that include oils, lard, sugar and salt.
Group 3 are “processed foods” such as canned vegetables, canned fruit with syrup, canned fish in oil, some processed foods of animal origin (ham, bacon, pastrami, smoked fish) and natural cheese with added salt These foods are made by adding processed culinary ingredients to unprocessed and minimally processed foods.
Group 4, “ultra-processed foods”, are formulations of ingredients, usually created by a series of industrial techniques. They are made by deconstructing whole foods, altering them and then recombining them with additives to make them convenient, appealing and hyper-palatable.
The latest findings
For the study, researchers from Harvard University and Tufts University examined the association between ultra-processed foods and colorectal cancer risk among 206,248 men and women who were followed for up to 28 years.
Participants completed diet questionnaires every four years and provided information on medical and lifestyle factors every two years. The researchers assigned the foods the participants consumed to a NOVA food group.
During the study, 3,216 cases of colorectal cancer occurred.
Overall, men whose diets contained the most ultra-processed foods had a 29 percent greater risk of developing colorectal cancer than those whose diets contained the least amount. There was no link between ultra-processed foods and cancer risk in women.
What is the healthiest way to cook vegetables to maximize their nutritional value?
The researchers analyzed subgroups of ultra-processed foods and found that ready-to-eat food products made with meat, poultry and seafood, as well as sugary drinks, were linked to an increased risk of colorectal cancer in men.
It is not clear why an association between ultra-processed foods and colon cancer risk was not observed in women. Women may make different ultra-processed food choices than men. Sex hormones may also be involved.
The colorectal cancer risk attributed to ultraprocessed foods was largely independent of risk factors such as body mass index and poor diet quality, suggesting that other aspects of ultraprocessed foods are to blame for the development of colorectal cancer. colon
Beyond the poor quality of the diet
Ultra-processed foods contain additives, such as emulsifiers and artificial sweeteners, some of which can alter the composition of the gut microbiome in a direction that promotes inflammation.
Potential carcinogens can also form during food processing. Acrylamide, for example, produced when foods are heated to high temperatures (eg chips, crisps, cereal products), has been linked to increased oxidative stress and inflammation.
Ultra-processed foods can also contain contaminants that carry over from their plastic packaging, such as bisphenol A. Additionally, during processing these foods are stripped of the protective phytochemicals and nutrients found in whole foods.
What to do?
The latest findings add to growing evidence that both the nutritional quality and degree of food processing need to be considered when assessing the relationship between diet and health and when revising guidelines dietary
Some progress is being made. Canada’s food guide, for example, updated in 2019, advises limiting intake of highly processed foods.
Make a list of the ultra-processed foods that you and your family eat regularly. Put strategies in place to buy them less often.
Make homemade versions of commercially prepared granola bars, baked goods, pasta sauce, soups, and salad dressings. Roast turkey breast or grilled chicken for sandwiches and salads.
Choose whole, lightly processed snacks like popcorn, whole, unsweetened nuts, dried fruit, and plain yogurt. As often as possible, choose foods with ingredients you’ll find in your pantry.
Leslie Beck, a dietitian in private practice based in Toronto, is director of food and nutrition at Medcan. Follow her on Twitter @LeslieBeckRD
Sign up for the weekly Health and Wellbeing newsletter to receive the latest news and advice.