New study links ultra-processed foods and colorectal cancer in men

For many Americans, the convenience of precooked and instant meals can make it easy to overlook less-than-ideal nutritional information, but a team led by researchers from Tufts University and Harvard University hopes that will change after discovering recently a link between high consumption of ultra-processed foods and an increased risk of colorectal cancer.

In a study published August 31 in the BMJresearchers found that men who ate high rates of ultra-processed foods had a 29 percent increased risk of developing colorectal cancer—the third most diagnosed cancer in the United States—than men who ate much smaller amounts. They did not find the same association in women.

“We started out thinking that colorectal cancer might be the cancer most affected by diet compared to other cancers,” said Lu Wang, lead author of the study and a postdoctoral fellow in the Friedman School of Nutrition Science and Policy at Tufts. “Processed meats, most of which fall into the ultra-processed food category, are a strong risk factor for colorectal cancer. Ultra-processed foods are also high in added sugars and low in fiber, which that contributes to weight gain and obesity, and obesity is an established risk factor for colorectal cancer.

The study looked at the responses of more than 200,000 participants (159,907 women and 46,341 men) in three large prospective studies that evaluated dietary intake and were carried out for more than 25 years. Each participant was given a food frequency questionnaire every four years and asked about the frequency of consumption of approximately 130 foods.

For the study in BMJ, the participants’ ultra-processed food intake was classified into quintiles, with a value ranging from the lowest consumption to the highest. Those in the highest quintile were identified as having the highest risk of developing colorectal cancer. Although a clear link was identified for men, particularly in cases of colorectal cancer in the distal colon, the study did not find an overall higher risk for women who ate higher amounts of ultra-processed foods.

The impacts of ultra-processed foods

The analyzes revealed differences in the ways men and women consume ultra-processed foods and the possible associated cancer risk. Of the 206,000 participants followed for more than 25 years, the research team documented 1,294 cases of colorectal cancer among men and 1,922 cases among women.

The team found that the strongest association between colorectal cancer and ultra-processed foods among men comes from ready-to-eat meat, chicken or fish-based products. “These products include some processed meats such as sausage, bacon, ham, and fish cakes. This is consistent with our hypothesis,” Wang said.

The team also found that higher consumption of sugar-sweetened beverages, such as soft drinks, fruit-based drinks and sweetened milk-based beverages, is associated with an increased risk of colorectal cancer in men.

However, not all ultra-processed foods are equally harmful when it comes to colorectal cancer risk. “We found an inverse association between ultra-processed dairy products such as yogurt and colorectal cancer risk among women,” said co-senior author Fang Fang Zhang, a cancer epidemiologist and acting chair of the Division of Nutrition, Epidemiology and Science at Data from the Friedman School. .

Overall, there was no relationship between ultra-processed food consumption and colorectal cancer risk among women. It is possible that the composition of ultra-processed foods consumed by women is different from that of men.

“Foods like yogurt can potentially counteract the harmful impacts of other types of ultra-processed foods on women,” said Zhang.

Study co-senior author Mingyang Song, an assistant professor of clinical epidemiology and nutrition at the Harvard TH Chan School of Public Health, added that “further research will be needed to determine whether there is a true sex difference in the associations, or whether the findings nulls in the women in this study were simply due to chance or other uncontrolled confounders in the women that mitigated the association.”

Although ultra-processed foods are often associated with poor diet quality, there could be factors beyond the poor dietary quality of ultra-processed foods that affect the risk of developing colorectal cancer.

The potential role of food additives in altering the gut microbiota, promoting inflammation, and contaminants formed during food processing or migrated from food packaging may promote cancer development, Zhang noted.

Analyzing the data

With a follow-up rate of over 90% for each of the three studies, the research team had a wealth of data to process and review.

“Cancer takes years or even decades to develop, and from our epidemiological studieswe have shown the possible latency effect: it takes years to see an effect of a certain exposure on cancer risk,” Song said. “Because of this long process, it is important to have long-term exposure to the data to better assess the cancer risk. “

The studies included:

After a process of exclusion for previous diagnoses or incomplete surveys, the researchers were left with prospective data on 159,907 women from both NHS studies and 46,341 men.

The team adjusted for potential confounding factors, including race, family history of cancer, endoscopy history, hours of physical activity per week, smoking, total alcohol and total caloric intake, regular use of aspirin and menopausal status.

Zhang is aware that since all the participants in these studies worked in the health care field, the findings for this population may not be the same as those for the general population, as participants may be more inclined to eat healthier and stay away from ultra-processed foods. The data may also be skewed because the processing has changed in the last two decades.

“But we are comparing within that population those who consume higher amounts with lower amounts,” Zhang said. “So those comparisons are valid.”

Change dietary patterns

Wang and Zhang previously published a study that identified a trend in the increased consumption of ultra-processed foods in American children and adolescents. Both studies underscore the idea that many different groups of people may rely on ultra-processed foods in their daily diets.

“Much of the dependence on these foods may be due to factors such as food access and convenience,” said Zhang, who is also a fellow at the Tufts Institute for Global Obesity Research. “Chemically processed foods can help extend shelf life, but many processed foods are less healthy than unprocessed alternatives. We need to make consumers aware of the risks associated with eating unhealthy foods in quantity and make make healthier options easier to choose.

Wang knows that change will not happen overnight and hopes that this study, among others, will contribute to changes in dietary recommendations and regulations.

“Long-term change will require a multi-step approach,” added Wang. “Researchers continue to examine how nutrition-related policies, dietary recommendations, and changes in recipes and formulas, along with other healthy lifestyle habits , can improve overall health and reduce the burden of cancer. It will be important for us to continue to study the link between cancer and diet, as well as potential interventions to improve outcomes.”