Ultra-processed foods linked to colorectal cancer risk, study finds

Many large studies conducted over long periods of time have shown that consuming a diet rich 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 – e.g. soft drinks, packaged sweet and savory snacks, margarine, mass-produced breads, instant noodles, sausages, hot dogs, pre-cooked/ready-to-heat meals , ice cream, cookies, pastries, cake mixes, sweetened yogurt – are high in calories, unhealthy fats, added sugars and sodium, while being low in fiber, vitamins and minerals.

Now, a study published Aug. 31 in The BMJ has linked a high intake of ultra-processed foods to an increased risk of colorectal cancer at men’s. The findings 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 based on the extent of their processing. Group 1 includes “unprocessed products [natural] and minimally processed foods,” which are natural foods modified by processes such as drying, grinding, filtering, roasting, fermentation, pasteurization, and freezing.

Group 2 foods are “processed culinary ingredients”, including oilslard, sugar and salt.

Group 3 includes “processed foods” such as canned vegetables, canned fruit in syrup, canned fish in oil, some processed animal food (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 foodsby modifying them and then recombining them with additives to make them practical, attractive and hyper-appetizing.

The latest finds

For the study, researchers from Harvard University and Tufts University examined the association between ultra-processed foods and colorectal cancer risk in 206,248 men and women who were followed for up to 28 years. .

Participants completed dietary questionnaires every four years and provided information on medical and lifestyle factors every two years. The researchers assigned the foods eaten by the participants 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% higher risk of developing colorectal cancer than those whose diets contained the least. There was no link between ultra-processed foods and cancer risk in women.

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Researchers looked at subgroups of ultra-processed foods and found that ready-to-eat meat, poultry and seafood products, as well as sugary drinks, were linked to a higher risk. colorectal cancer in men.

It is unclear why an association between ultra-processed foods and colon cancer risk has not been observed in women. It is possible that women make different ultra-processed food choices than men. Sex hormones may also be involved.

The risk of colorectal cancer attributed to ultra-processed foods was largely independent of risk factors such as body mass index and poor diet quality, suggesting that other aspects of ultra-processed foods are at risk. blame in the development of colon cancer.

Beyond poor food quality

Ultra-processed foods contain additives, such as emulsifiers and artificial sweeteners, some of which can alter the composition of the gut microbiota in a direction that favors inflammation.

Potential carcinogens can also be formed during food processing. Acrylamide, for example, produced when foods are heated to high temperatures (eg french fries, potato chips, grain products), has been associated with increased oxidative stress and inflammation.

Ultra-processed foods may also contain contaminants that transfer 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 the nutritional quality and degree of processing of foods should be taken into account when assessing the relationship between diet and health and when reviewing dietary guidelines.

Some progress is underway. Canada’s food guidefor example, updated in 2019, advises limiting the consumption of highly processed foods.

Make a list of ultra-processed foods that you and your family eat regularly. Implement strategies to buy them less often.

Make homemade versions of store-bought granola bars, pastries, pasta sauces, soups and dressings. Roast turkey breast or grill chicken for sandwiches and salads.

Choose integer and minimally processed snacks such as popcorn, whole, unsweetened dried fruits, nuts, and plain yogurt. As often as possible, choose foods with ingredients that you can find in your own pantry.

Leslie Beck, a dietitian in private practice in Toronto, is director of food and nutrition at Medcan. Follow her on Twitter @LeslieBeckRD

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