Evidence linking processed foods to serious health problems like cancer and even death continues to mount.
A pair of studies published Wednesday highlight the risk of frequently eating foods such as hot dogs, cheese puffs, sodas and fries.
The first studywhich examined more than 24,000 adults in Italy, found that those who ate large amounts of ultra-processed foods had a higher risk of death overall, and death from heart disease in particular, compared to people who ate less foods in this category.
The second study followed more than 200,000 American health care workers over a period of 24 to 28 years and found that men who ate a lot of ultra-processed foods – more than nine servings a day, on average – had a risk of cancer colorectal 29% higher than men who ate about three servings daily.
Fang Fang Zhang, lead author of the second study and an associate professor at Tufts University, said the group with the highest consumption of ultra-processed foods likely got about 80% of their daily calories from these foods. The US average is about 57%.
The study did not find an association between the consumption of ultra-processed foods and colorectal cancer in women, although scientists are unsure why. One theory is that higher levels of estrogen might have a protective effect, Zhang said. But the result could also be an anomaly, since most risk factors for colorectal cancer are similar for both sexes.
Foods considered “ultra-processed” contain more artificial ingredients than those that are simply processed by adding salt, sugar or oil. Ultra-processed foods typically contain very few whole ingredients and contain flavorings, colorings, or other additives. Condiments, microwaveable dinners, packaged donuts, and ice cream, for example, all fall under this label.
“It’s sort of an attempt to get a definition of junk food, which I think we all kind of know when we see it,” said Walter Willett, professor of epidemiology and nutrition at Harvard. TH Chan School of Public Health which was not involved in either study.
Because the colon and rectum are “on the front line of our diet” as part of our digestive system, Willett said, “colorectal cancer appears to be more directly related to diet than most other cancers.”
Rates of colorectal cancer have increased among young adults in recent decades. A study from the American Cancer Society found that colon cancer rates have increased each year among people aged 20 to 39 since the mid-1980s, and the share of rectal cancer among adults under 55 doubled from 1989-90 to 2012-13.
“Diet likely plays a role in the rise in obesity that we continue to see, and we know that obesity is also associated with colorectal cancer and other cancers,” said Caroline Um, lead scientist at the American Cancer Society. “We are seeing more and more obese young adults [and] having obesity-related things, like diabetes and metabolic syndrome.
However, the new health care worker study found that ultra-processed foods were associated with colorectal cancer in men regardless of their body mass index.
The researchers therefore suggested that chemical additives in food or synthetic chemicals in packaging could be partly responsible for this trend. Many processed meats contain nitrates and nitrites, preservatives that may increase cancer risk.
“Red and processed meat have been shown to fairly consistently increase the risk of colorectal cancer,” Zhang said.
His study found that processed meat products like hot dogs, salami and sausages, as well as sugary drinks, were particularly correlated with a risk of colorectal cancer in men.
The Italian study also found that poor nutritional quality – defined as an unhealthy balance of sugar, fiber and fat – alone did not explain the association of ultra-processed foods with higher mortality. So Marialaura Bonaccio, the author of the study, said that the chemical additives probably contribute to the observed negative health effects.
“Diet Coke may be considered nutritionally good — for example, Diet Coke without sugar because it doesn’t contain sugar — but Diet Coke isn’t even a food,” she said. “It’s a combination of chemicals.”
Bonaccio’s study proposes labeling foods according to their degree of processing, in addition to their nutritional quality, to help people make healthier choices. But other experts believe the change may not impact those most at risk.
“A labeling policy sometimes works for people who have a high level of education or income because they pay attention to labels or know how to read labels,” Zhang said. But the labels might be less effective for underserved groups, she added, and those communities often consume more ultra-processed foods because the items tend to be cheap, quick to prepare and last longer. on a shelf.
As a general rule, Willett said, “Processed meat should be consumed infrequently, consumption of sugary drinks should be occasional at most.” [and] foods high in saturated fat should be kept low.
Still, some ultra-processed foods are healthier than others. Breakfast cereals and whole-grain bread, for example, can be sources of dietary fibre, which could reduce the risk of heart disease Where cancer.
Scientists have yet to identify the precise level of consumption of ultra-processed foods that constitutes a health risk.
“We don’t really know: is there a safe amount, or is an amount not good?” Uh said.