Ultraprocessed foods tied 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 it 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, sweet and salty packaged snacks, margarine, mass-produced breads, instant noodles, sausages, hot dogs, pre-cooked/ready-to-heat meals, ice cream, cookies, cakes, pies mixes, sweetened yogurt: These are high in calories, unhealthy fats, added sugars, and sodium, while low in fiber, vitamins, and minerals.

Now, a study published August 31 in The BMJ has linked a high intake of ultra-processed foods with an increased risk of colorectal cancer in men The findings also suggest that the attributes of these foods, beyond the poor quality of the nutrients, 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 degree of processing. Group 1 includes “unprocessed [natural] and minimally processed foods”, which are natural foods altered by processes such as drying, grinding, filtering, roasting, fermenting, pasteurizing and freezing.

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

Group 3 are “processed foods” such as canned vegetables, canned fruit in 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, generally created through a series of industrial techniques. They are made by deconstructing whole-grain foodsaltering them and then recombining them with additives to make them convenient, attractive and hyperpalatable.

latest finds

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.

The participants completed dietary questionnaires every four years and provided information on medical and lifestyle factors every two years. The researchers assigned the foods the participants ate 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 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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The researchers looked at subgroups of ultra-processed foods and found that ready-to-eat food products made from meat, poultry, and seafood, as well as sugar-sweetened beverages, were linked to an increased risk of colorectal cancer in men.

It’s not clear why an association between ultra-processed foods and colon cancer risk in women was not seen. Women may choose ultra-processed foods differently than men. Sex hormones may also be involved.

Colorectal cancer risk 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 to blame of the development of colon cancer.

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 be formed during food processing. Acrylamide, for example, which is produced when foods are heated to high temperatures (eg, French fries, potato chips, 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. Also, during processing, these foods lose the protective phytochemicals and nutrients found in whole foods.

To do?

The latest findings add to growing evidence that both the nutritional quality and degree of processing of foods need to be taken into account when assessing the relationship between diet and health and when revising dietary guidelines.

Some progress is being made. Canada food guidefor example, updated in 2019, it advises limiting the intake 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 commercially prepared granola bars, baked goods, pasta sauce, soups, and salad dressings. Grill a turkey breast or roast chicken for sandwiches and salads.

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

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

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