Ultra-processed foods linked to heightened risk of cancer: major BMJ study

15 Feb 2018 --- Although processed foods have long been thought to be significantly less healthy than non-processed foods, an observational study published yesterday in BMJ has added some stark figures to the link between ultra-processed foods and the risk of cancer. The study concluded that a 10 percent increase in the proportion of ultra-processed foods in the diet is associated with increases of 12 percent in the risk of overall cancer and 11 percent in the risk of breast cancer.

The study involved nearly 105,000 French adults (22 percent men; 78 percent women) with an average age of 43 years. Participants’ dietary intakes were collected using repeated 24-hour dietary records, designed to register their usual consumption for 3,300 different food items. Cases of cancer were identified from participants' declarations validated by medical records and national databases over an average of five years. Several well-known risk factors for cancer, such as age, sex, educational level, family history of cancer, smoking status and physical activity levels, were taken into account.

In the study, food items were categorized according to their degree of processing by the NOVA classification.

Ultra-processed foods include packaged baked goods and snacks, fizzy drinks, sugary cereals, ready meals and reconstituted meat products - often containing high levels of sugar, fat, and salt, but lacking in vitamins and fiber. 

According to the researchers, they are thought to account for up to 50 percent of total daily energy intake in several developed countries.

Further testing found no significant association between less processed foods (such as canned vegetables, cheeses and freshly made unpackaged bread) and risk of cancer, while consumption of fresh or minimally processed foods (fruits, vegetables, pulses, rice, pasta, eggs, meat, fish and milk) was associated with lower risks of overall cancer and breast cancer.

This is an observational study, so no firm conclusions can be drawn about cause and effect, and there are some clear limitations. For example, the researchers cannot rule out some misclassification of foods or guarantee detection of every new cancer case. Nevertheless, the study sample was large and they were able to adjust for a range of potentially influential factors.

They stress that further work is needed to better understand the effects of the various stages of processing, but suggest policies targeting product reformulation, taxation, and marketing restrictions on ultra-processed products and promotion of fresh or minimally processed foods may contribute to primary cancer prevention.

“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,” the researchers conclude.