Ultra-processed foods like sugary drinks and fish sticks might increase cancer risk, according to findings from the large French NutriNet-Santé cohort study of 104,980 adults.
“A 10% increase in the proportion of ultra-processed foods in the diet was associated with a significant increase of more than 10% in the risks of overall and breast cancer,” the team reported in BMJ. “If confirmed in other populations and settings, these results suggest that the rapidly increasing consumption of ultra-processed foods may drive an increasing burden of cancer in the next decades.”
These foods contain high levels of sugars, saturated fats, and additives, as well as chemical compounds created during industrial-scale preparation processes (such as baking, frying, and hydrogenation) that are not found in less-processed foods. Examples include mass-produced packaged cakes, breads, and fruit-filling pies; soda drinks; chicken and fish nuggets; reconstituted meats preserved with nitrites or other additives; and instant soups and noodles.
A 2016 analysis of dietary intake of ultra-processed foods in the United States, using data from the National Health and Nutrition Examination Survey, found that these foods represent 58% of sugar intake by the average American.
The French research team analyzed daily dietary self-reports for the NutriNet-Santé cohort from between 2009 and 2017, calculating participants’ regular consumption for 3,300 food items. Sugary snacks represented 26% of the total intake of ultra-processed food, followed by sugary drinks (20%), breakfast cereals and other starchy foods (16%), and ultra-processed fruits and vegetables (15%). Processed meats, fish, and egg products represented another 12% of the ultra-processed food intake in the French cohort.
At a median follow-up of 5 years, 2,228 people in the cohort had been diagnosed with cancer. Overall cancer risk was associated with dietary intake of ultra-processed foods (hazard ratio [HR], 1.12; 95% CI, 1.06–1.18; P < .001). Subgroup analyses found that the association was also significant for breast cancer (HR, 1.11; 95% CI, 1.02–1.22; P = .02) but not for prostate or colorectal cancers.
The associations for both overall cancer risk and breast cancer risk remained statistically significant in multivariate analyses adjusted for sex, age, tobacco smoking, physical activity, and other dietary indicators of nutritional quality, the authors reported. (However, because their study design was observational and self-reported by cohort participants, statistical confounding by other variables was possible.)
A link between ultra-processed foods and cancer risk seems to be biologically plausible. Ultra-processed foods are known to be of lower nutritional quality and contain additives and chemical compounds formed in production and processing. They are high in sugar, saturated fats, and fiber-depleted starches, and have been linked in a handful of cohort and cross-sectional studies to dyslipidemia, weight gain, overweight and obesity status, hypertension, and metabolic syndrome. Obesity, in turn, has been reported to be associated with metabolic syndrome and increased breast cancer risk in women.
“Although epidemiological data relating to cancer risk are lacking, mechanistic studies suggest potential carcinogenic effects of several components commonly found in ultra-processed foods,” the French study team noted.