Ultra-Processed Foods Promote Colorectal Cancer in Men

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The bachelor life can be great... with the exception of frozen meals. Recent research done by scientists from Tufts and Harvard Universities revealed that men who eat ultra-processed foods frequently had a bigger risk of developing colorectal cancer compared to those who did not.

The recent study was published in The BMJ. It was discovered that men who ate more ultra-processed foods had a 29% higher risk of the development of colorectal cancer than men who ate much less. This association was not observed in women. In the US, colorectal cancer is the third most diagnosed type of cancer.

Lu Wang, the study's lead author and a postdoctoral fellow at the Friedman School of Nutrition Science and Policy at Tufts states his team believed that colorectal cancer, compared to other cancers, might be the most affected by diet. Ultra-processed foods include processed meats and foods high in refined sugar. They also tend to be low in fiber and may contribute to obesity, a known risk factor for colorectal cancer. 

The study in over 200,000 subjects of which 159,907 were women and 46,341 were men, evaluated responses to dietary intake. The study used data from three large prospective studies that spanned 25 years. Subjects were given food frequency questionnaires every four years and queried about how often roughly 130 foods were eaten.

In this study, consumption of ultra-processed food was divided into quintiles that ranged from lowest intake to highest intake. Individuals with the highest intake were seen the most likely to develop colorectal cancer. While a clear association was observed in men, especially for colorectal cancer in the distal colon, the research did not see the same overall risk in women that ate large amounts of ultra-processed foods. 

The Effects of Ultra-Processed Foods

Results of this study found variable ways that men and women ate ultra-processed foods and the potential for cancer risk. In the 206,000 subjects followed for over 25 years, 1,294 colorectal cancer cases were seen in men and 1,922 cases were observed in women.

In men, the strongest link between ultra-processed foods and colorectal cancer came from the intake of meat, poultry, or fish-based convenience products such as sausage, bacon, ham, and fish cakes. Wang notes this was consistent with their hypothesis. 

Higher intake of sugary beverages including soda as well as fruit-based and sugary milk-based beverages were found to be linked with increased colorectal cancer risk in men.

Some ultra-processed foods were not harmful and may actually be protective, especially in women. These include processed dairy products such as yogurt, according to co-senior author Fang Fang Zhang, a cancer epidemiologist and interim chair of the Division of Nutrition Epidemiology and Data Science at the Friedman School.

A link between ultra-processed food intake and the risk for colorectal cancer was not seen in women. The researchers believe the composition of foods eaten by women are likely different than men’s choices. "Foods like yogurt can potentially counteract the harmful impacts of other types of ultra-processed foods in women," Zhang said.

Additional research should be completed to show if a true sex difference is present in the associations or if the lack of findings in women was simply due to chance or an uncontrolled confounding variable, states Mingyang Song, co-senior author on the study and assistant professor of clinical epidemiology and nutrition at the Harvard T.H. Chan School of Public Health.

Poor diet quality is often linked with the intake of ultra-processed foods, but other factors could affect the chance of developing colorectal cancer, too. Food additives that change gut microbiota and promote inflammation or contaminants created in food processing or travel could raise the risk of cancer development, states Zhang. 

Evaluating the Data

The study data came from three large studies including 

  • The Nurses' Health Study (1986-2014): 121,700 registered female nurses between the ages of 30 and 55
  • The Nurses' Health Study II (1991-2015): 116,429 female nurses between the ages of 25 and 42
  • The Health Professional Follow-up Study (1986-2014): 51,529 male health professionals between the ages of 40 and 75.

The scientists had plenty of data to evaluate given over a 90% follow-up rate from each study.

"Cancer takes years or even decades to develop, and from our epidemiological studies, we have shown the potential latency effect -- it takes years to see an effect for certain exposure on cancer risk," said Song. "Because of this lengthy process, it's important to have long-term exposure to data to better evaluate cancer risk.".

After weeding out past cancer diagnoses and incomplete surveys, Zhang’s research team had data from nearly 160,000 women from the NHS studies and over 46,000 men. Confounding variables included race, family history of cancer, prior endoscopy, physical activity per week, smoking, total alcohol use, total energy intake, aspirin use, and menopausal status. 

Zhang notes that subjects in these studies work in healthcare and results in this population could be different than the general population. Subjects may consume more nutritious foods and shy away from ultra-processed foods. Information from the study may also be distorted since food processing has changed during the past twenty years. However, the comparisons were done within the population, and therefore valid, notes Zhang.

Changing Diet Patterns

Prior research from Wang and Zhang showed a trend of higher intake of ultra-processed food intake in US children and teens. Their studies highlighted the fact that various populations consume ultra-processed foods on a regular basis. 

Zhang, as a member of the Tufts Institute for Global Obesity Research, is aware that consumption of these foods may be due to convenience and food access. "Chemically processing foods can aid in extending shelf life, but many processed foods are less healthy than unprocessed alternatives. We need to make consumers aware of the risks associated with consuming unhealthy foods in quantity and make the healthier options easier to choose instead."

Wang states that the changes in the food system will take time. Researchers will keep evaluating the impact of nutrition-related policies, dietary recommendations, and recipe and formula adjustments along with healthy lifestyle habits that may prevent cancer and improve overall health. Studies need to continue to evaluate the risk of diet and cancer, as well as ways to improve outcomes. 

Advice for Clinicians:

  • Push produce and the protective power of plants.
  • Offer lessons in simple cooking skills to reduce reliance on ultra-processed foods.
  • Teach clients how to read food labels.
  • Encourage affordable, plant-based meals.
  • Discourage intake of processed meats, desserts, and convenience foods.
  • Refer clients for smoking cessation if needed.
  • Discuss alcohol intake and physical activity as it relates to cancer and overall health.

By Lisa Andrews, MEd, RD, LD

Reference:

Lu Wang, Mengxi Du, Kai Wang, Neha Khandpur, Sinara Laurini Rossato, Jean-Philippe Drouin-Chartier, Euridice Martínez Steele, Edward Giovannucci, Mingyang Song, Fang Fang Zhang. Association of ultra-processed food consumption with colorectal cancer risk among men and women: results from three prospective US cohort studiesBMJ, 2022; e068921 DOI: 10.1136/bmj-2021-068921

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