Ultra-processed foods, such as ready-to-eat meat, fizzy drinks, ice cream and sugary cereals are linked to a higher risk of early death, according to a new study.
The U.S.-based research, published Wednesday in the British Medical Journal (BMJ), found that over a span of 34 years, people who consumed a greater quantity of highly-processed foods (averaging seven servings per day) faced an increased risk of mortality compared to those who consumed fewer servings (averaging three servings per day).
“The association is quite linear. The higher intake of ultra-processed foods, the higher mortality,” said Mingyang Song, senior author and associate professor of clinical epidemiology and nutrition at Harvard T.H. Chan School of Public Health.
Not all ultra-processed food products should be universally restricted, Song said, but the findings provide support for limiting the consumption of certain types of ultra-processed food, like processed meats, for long-term health.
What are ultra-processed foods?
Ultra-processed foods go through multiple processes such as extrusion, molding, milling, etc., and contain many added ingredients and are highly manipulated, according to the Heart and Stroke Foundation. Processed foods, meanwhile, refer to foods where ingredients such as oil, sugar or salt are added, and they are packaged.
Ultra-processed foods encompass a wide range of products, including packaged baked goods, candy, chips, sweetened drinks, bacon and hot dogs. These items are laden with additives, sugars and unhealthy fats, and also lack essential nutrients like vitamins and fibre, explained Amanda Nash, a registered dietician with the Heart and Stroke Foundation.
The prevalence of these foods is also increasing in high-income countries such as Canada, according to the Heart and Stroke Foundation. A 2015 study by the organization found that Canadians get nearly 50 per cent of their daily calories from ultra-processed foods.
“We know that Canadians are the second-largest buyers of ultra-processed foods and drinks in the world, second only to Americans,” Nash said. “The purpose of an ultra-processing is to create a product that’s going to be convenient. That means it’s durable, it’s ready to eat, ready to heat, or ready to drink. It’s attractive and it’s profitable, generally using cheaper ingredients.”
Consuming highly-processed foods has already been linked to various health risks such as obesity, heart disease, diabetes and colon cancer. However, Song argued while other studies have examined the connection between ultra-processed food and mortality, they often suffer from limitations such as small sample sizes and shorter durations.
To address this knowledge gap, Song and his team tracked the long-term health of more than 74,000 female registered nurses from 11 U.S. states in the Nurses’ Health Study (1984 to 2018) and more than 39,500 male health professionals from all 50 U.S. states in the Health Professionals Follow-up Study (1986 to 2018) with no history of cancer, cardiovascular diseases or diabetes at study enrolment.
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Every two years participants provided information on their health and lifestyle habits, and every four years they completed a detailed food questionnaire.
During an average 34-year follow-up period, the researchers identified 48,193 deaths, including 13,557 deaths due to cancer, 11,416 deaths due to cardiovascular diseases, 3,926 deaths due to respiratory diseases, and 6,343 deaths due to neurodegenerative diseases.
Compared with participants in the lowest quarter of ultra-processed food intake (average three servings per day), those in the highest quarter (average seven servings per day) had a four per cent higher risk of total deaths and a nine per cent higher risk of other deaths, including an eight per cent higher risk of neurodegenerative deaths.
What are the biggest culprit foods?
Ready-to-eat meats showed the strongest association with mortality, the study found.
Other subgroups also showed an association with higher mortality, including sugar-sweetened and artificially sweetened beverages, dairy-based desserts (like ice cream and yogurt) and ultra-processed breakfast foods excluding whole grains.
When further separating sugar-sweetened and artificially sweetened beverages, the researchers found “a generally stronger association for sugar-sweetened than artificially sweetened beverages.”
Song said his team was not surprised to find that processed meats (like ham, sausage, bacon and deli meats) and fizzy drinks were linked to higher mortality rates, as there has been “very compelling data indicating they cause adverse effects.”
For example, in 2015, the World Health Organization classified processed meat as “carcinogenic to humans based on sufficient evidence in humans that the consumption of processed meat causes colorectal cancer.”
While hot dogs and jerky sticks weren’t surprising findings for the BMJ authors, Song said the researchers were taken aback by the unexpected risks associated with other foods.
“What surprised us was the other categories, like ice cream and dairy-based desserts because the data have been very mixed. And, we were surprised to see the positive association,” he said.
He added that while certain foods, like breakfast cereals, may fall under the highly processed category, it doesn’t necessarily mean they’re bad for you, as many contain high fiber and added vitamins and minerals.
Hazards of ultra-processed foods
This isn’t the first study to link health risks with consuming ultra-processed foods.
On Feb. 28, a review of hundreds of epidemiological studies published in the BMJ found that higher exposure to ultra-processed foods is associated with an increased risk of 32 damaging health outcomes including cancer, major heart and lung conditions, mental health disorders and early death.
The report noted that ultra-processed foods, which include packaged baked goods and snacks, fizzy drinks, sugary cereals, and ready-to-eat or heat products undergo multiple industrial processes.
Another study published in October 2023 in the BMJ argued that ultra-processed foods can be so addictive that they can cause withdrawal symptoms similar to people trying to quit smoking.
Canada’s food guide advises limiting highly-processed foods to avoid excessive intake of sodium, sugars or saturated fat, as they can elevate the risk of chronic diseases.
Excessive sodium consumption, for instance, can raise blood pressure, potentially leading to heart disease. Consuming significant amounts of foods and drinks with added sugars has been associated with a heightened risk of obesity and Type 2 diabetes, Health Canada says.
Processed foods may also be linked to poor health because it disrupts a healthy gut microbiome, Song explained.
“The bacteria in our gut system gets altered by the heavy consumption of these foods and this change can lead to immune disturbance,” he said. “So our immune system wouldn’t be able to stop this early development of cancer and cardiovascular diseases.”
What's next?
While the study highlights a correlation between certain ultra-processed foods and increased mortality rates, Song emphasizes the need for further studies. This is because his study was observational, meaning no firm conclusions can be drawn about cause and effect.
Despite the limitation of the study, the researchers concluded that the findings provide support for limiting consumption of certain types of ultra-processed food for long-term health.
“But we don’t want people to be freaked out about the concept of ultra-processed food,” Song said. “I think the overall dietary quality remains to be the key determinant of health outcomes. So, in other words, if a person consumes a generally healthy diet and has some amount of ultra-processed food (that) wouldn’t be too terrible.”
Maintaining a healthy diet is crucial for reducing the risk of heart disease and stroke, explained Nash.
This involves incorporating plenty of vegetables, fruits, whole grains, and protein sources into meals while minimizing highly processed foods and avoiding sugary beverages. She added that cooking at home and enjoying meals with loved ones are key aspects of a balanced diet.
Nash recommends turning to minimally processed foods such as canned beans or frozen vegetables.
“Some of these foods that have a higher shelf life, and we can stock up on them when they’re on sale to make easier meals at home,” she said.
— with files from Global News’ Uday Rana
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