Cancer survivors eating certain food types could face sharply higher risk of death

Cancer survivors consuming high amounts of ultraprocessed foods (UPFs) may face a significantly higher risk of death, even if the cause is unrelated to the disease itself.

A new study from the American Association for Cancer Research linked increased consumption of these largely ready-to-eat, high-sugar, high-salt and high-additive foods to an increased risk of all-cause and cancer-specific mortality.

"What people eat after a cancer diagnosis may influence survival, but most research in this population has focused only on nutrients, not how processed the food is," said lead author Marialaura Bonaccio, Ph.D., of the Research Unit of Epidemiology and Prevention at IRCCS Neuromed in Pozzilli, Italy, in a press release.

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UPFs are often low in essential nutrients and contain additives, artificial flavorings, preservatives, and high levels of added sugars and unhealthy fats that the body may not process well, according to nutritionists.

"The substances involved in the industrial processing of foods can interfere with metabolic processes, disrupt gut microbiota and promote inflammation," Bonaccio said. 

"As a result, even when an ultraprocessed food has a similar calorie content and nutritional composition on paper compared to a minimally processed or ‘natural’ food, it could still have a more harmful effect on the body."

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In the study, researchers followed more than 24,000 individuals from 2005 to 2022. Among this group, 802 cancer survivors provided dietary information via a questionnaire from the European Prospective Investigation into Cancer and Nutrition (EPIC), according to the press release.

All participants were 35 or older and lived in the Southern Italian region of Molise.

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UPFs were defined using the NOVA classification system, a widely used framework that classifies foods based on the extent of industrial processing. 

The team examined seven specific categories of ultraprocessed items, including processed meats, salty snacks, sugary sweets and dairy products containing additives.

To measure intake, the researchers used two metrics: weight ratio (total weight of UPFs compared to all food consumed daily) and energy ratio (percentage of daily calories derived from UPFs).

During a median follow-up of 14.6 years, survivors in the highest third of UPF consumption by weight had a 48% higher rate of death from any cause and a 57% higher rate of death from cancer than those in the lowest third, the researchers found.

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The study also revealed that increased inflammation and elevated resting heart rates accounted for approximately 37% of the link between UPFs and mortality.

The risk remained even after researchers accounted for how closely people followed a healthy Mediterranean-style diet.

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While some categories showed stronger links to mortality than others, Bonaccio cautioned against fixating on a single "bad" food. Instead, he stressed that the real problem is eating a diet largely made up of heavily processed, industrial foods.

"The negative health effects are not explained solely by poor nutrient profiles," Bonaccio said. "The level and nature of industrial food processing itself plays an independent role."

Based on the findings, the researchers suggest that cancer survivors carefully check labels, as foods containing more than five ingredients or any industrial additives are likely considered ultraprocessed.

"Focusing on the diet as a whole and shifting consumption toward fresh, minimally processed, home-cooked foods is the most meaningful approach," Bonaccio advised.

The study, which was published in the journal Cancer Epidemiology, Biomarkers & Prevention, had several limitations, the researchers acknowledged. 

Because the study was observational, it could not prove causality. It also relied on people reporting their own diets, which might not be perfectly accurate. 

Because diets were measured about eight years after diagnosis, the results may mostly reflect people who survived long enough to be included, which could skew the findings. As the study cohort was Italian, it may not apply to wider populations.