Eating fruits and vegetables reduces carcinogenic effects of red and processed meats: study

Recent research led by Katerina Maximova, an adjunct professor in the University of Alberta's School of Public Health and member of the Cancer Research Institute of Northern Alberta, shows that low consumption of fruits and vegetables combined with a higher intake of processed meats is associated with greater incidence of cancer for Albertans.

“It is generally accepted that red meat is a probable carcinogen, while there is convincing evidence that processed meats such as bacon and deli meats are, indeed, carcinogenic,” said Paul Veugelers, professor and co-author. 

Veugelers said this evidence is established by the World Health Organization’s Global Burden of Disease project, as well as the International Agency for the Research of Cancer, which has identified 15 cancers with possible links to consumption of red and processed meat. These include colorectal, stomach, esophagus, kidney, liver and other cancers. For cancer prevention, it is recommended to limit the amount of red meat and to avoid processed meat altogether.

Maximova, now Murphy Family Foundation Chair in Early Life Interventions and associate professor in the Dalla Lana School of Public Health at the University of Toronto, along with her School of Public Health colleagues, Veugelers and Irina Dinu, and their students tackled the complicated concept of co-consumption. They examined the co-consumption of red and processed meat along with foods that are recommended for cancer prevention—including fruits and vegetables, and whole grains and fibre—to note the effects on cancer rates, and how old people were at the time of their cancer diagnosis. 

“Much of the existing evidence focuses on the effect of single food items on cancer risk, but we don’t consume a particular food or nutrient in isolation,” explained Veugelers. “There is a need to understand the influence of a combination of factors involved in carcinogenesis, by looking at co-consumption.”

The study used data collected over more than 13 years from participants in Alberta’s Tomorrow Project, a long-term study tracking the health of more than 50,000 adults in the province. In addition to detailed dietary information, it offers a diverse range of data on participants’ demographics, behavioural characteristics and health.

Findings revealed that men with low intake of vegetables and fruit combined with a high intake of processed meat were 1.8 times as likely to develop one of the 15 cancers during followup. The corresponding risk for women was 1.5 times.

Men who ate a diet high in vegetables and fruit and low in processed meat had a 7.1 year longer time to diagnosis of the 15 cancers—80.4 years of age as opposed to 73.3. The difference in estimated median age for women was 6.3 years—79.3 versus 72.9 years of age for diagnosis.

“The carcinogenic effect of processed meats may be mitigated by following a healthy diet rich in non-starchy vegetables and fruit, particularly at lower levels of processed meat intake,” suggested Veugelers.

While researchers observed strong associations for processed meat, the findings for co-consumption of red meat with healthful foods were not as pronounced, although they did follow a similar pattern. This is consistent with convincing evidence that implicates processed meat in cancer incidence and only probable evidence for the role of red meat. 

Globally, in the 50 years spanning 1961 to 2014, annual per capita meat consumption almost doubled from 23 kilograms to 43 kilograms but remained static or declined in high-income countries. However, processed meat consumption remained the same. 

Veugelers acknowledged that red meat is an important source of protein, iron and other micronutrients, but added that consumption in western nations is too high. In the United States, adults consume an average of 1.47 servings of red meat per day, well above the recommendation of 1.0 serving per week. Processed meat consumption averages 0.87 servings per day, compared with the intake of none recommended by the World Cancer Research Fund/American Institute for Cancer Research. Canada has one of the highest per capita consumption rates in the world of 82.62 kilograms in 2017, and the consumption in Alberta ranks highest among Canadian provinces. 

Veugelers said there is still much research to be done on the interactions of co-consumed foods and their relation to cancer risks before health authorities can safely make specific recommendations, but he said it is critical that we consider what we eat.

“Diet is the single greatest modifiable risk factor for chronic diseases,” he stressed. “We stand to gain more health benefits from a healthy diet than from not smoking, or from more physical activity.”

He advised that consumers consider a diet that is varied, consistent with Canada’s new food guide, emphasizing vegetables, fruit, whole grains, and nuts and seeds. 

“It’s also important to balance healthful food choices with social benefits, because food brings us together and is to be enjoyed.”

The study, “Co-consumption of vegetables and fruit, whole grains, and fiber reduces the cancer risk of red and processed meat in a large prospective cohort of adults from Alberta's Tomorrow Project,” was published in the journal Nutrients.