Highly Processed Foods May Raise Overall Cancer Risk

Kristin Jenkins

February 15, 2018

A diet that includes a lot of highly processed foods loaded with sugar, fat, and salt may do more than raise the risk for overweight, obesity, type 2 diabetes, and heart disease, researchers warn.

Highly processed foods such as packaged baked goods, instant soups, reconstituted meats, frozen meals, and shelf-stable snacks also contain substances that may significantly increase overall risk for cancer and breast cancer, according to Mathilde Touvier, PhD, of the Sorbonne Paris Cité Epidemiology and Statistics Research Center in Paris, France, and colleagues.

The team reports results from a prospective study of more than 100,000 participants from the NutriNet-Santé cohort, published online February 14 in the BMJ.

They found that a 10% increase in the proportion of ultraprocessed foods in the diet was associated with an 11% increase in overall cancer risk [hazard ratio [HR], 1.12; P < .001). These foods included ultraprocessed fats and sauces (P = .002), as well as sugary products (P = .03) and drinks (P = .005).

"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 authors warn.

The rapidly increasing consumption of ultra-processed foods may drive an increasing burden of cancer in the next decades. Dr Mathilde Touvier and colleagues

They also note that many people worldwide are eating highly processed foods. Previous surveys that assessed individual food intake in Europe, the United States, Canada, New Zealand, and Brazil indicate that up to 50% of the total daily energy intake of people living in developed countries comes from highly processed foods and food products.

Increased Risk for Breast Cancer

The study also found that consumption of ultraprocessed foods was associated with a 12% increase in the risk for breast cancer (HR, 1.11; P = .02). Such products include those that contain a lot of sugar (P = .006)group.

No significant association was found between consumption of highly processed foods and an increased risk for prostate or colorectal cancer.

There was also no significant association between less processed foods and risk for cancer. These included canned vegetables, cheeses, and fresh, unpackaged bread.

Conversely, a diet consisting mostly of fresh or minimally processed foods, including fruits, vegetables, pulses, rice, pasta, eggs, meat, fish, and milk, was associated with a reduced risk for overall cancer and breast cancer, the study showed.

"These results remained statistically significant after adjustment for several markers of the nutritional quality of the diet (lipid, sodium, and carbohydrate intakes and/or a Western pattern derived by principal component analysis)," the study authors write.

Results Should Be Interpreted With Care

Because this is an observational study, no firm conclusions can be drawn about causality, Touvier told Medscape Medical News. "We need not be too alarmist. Caution is needed at this stage. These results need to be confirmed by other prospective cohorts, and deeper investigation [is needed] of the mechanisms involved."

In an accompanying editorial, Adriana Monge and Martin Lajous, MD, of the National Institute of Public Health in Mexico City and the Harvard T. H. Chan School of Public Health, in Boston, Massachusetts, called the results "interesting" but warned that they must be interpreted with care.

A lot more work is needed to provide the epidemiologic evidence that could shape public policy or lead to the development of actionable advice, the editorialists say.

"We are a long way from understanding the full implications of food processing for health and wellbeing," Monge and Lajous write. "The changing realities of the global food supply and the inherent limitations of epidemiologic studies call for more basic science, including data from animals, to inform further research on the effect of food processing on humans. Care should be taken to transmit the strengths and limitations of this latest analysis to the general public and to increase the public's understanding of the complexity associated with nutritional research in free living populations."

Empty Calories, Poor Nutrition

Processed foods are often characterized as offering empty calories and poor nutrition and having few vitamins and little or no fiber, Touvier and colleagues point out. Highly processed foods may contain additives and preservatives that enhance flavor and extend shelf life.

Experimental studies suggest that compounds formed during the production, processing, and storage of processed food may have carcinogenic properties. For instance, contaminants such as acrylamide can be produced during heat processing in processed fried potatoes, biscuits, bread, or coffee, the study authors say. "A recent meta-analysis found a modest association between dietary acrylamide and risk of both kidney and endometrial cancer in non-smokers," the write.

Acrylamide is considered "probably [a] human carcinogen by the International Agency for Research on Cancer and the National Toxicology Program, as previously reported by Medscape Medical News.

Study Details

For their study, the team used data from the ongoing Web-based NutriNetSanté cohort. Since May 2009, persons from the general population in France have been recruited in a study of the association between nutrition and health.

The study included 104,980 participants (mean age, 43 years) who were without cancer at baseline. The participants were enrolled from 2009 to 2017; 78% were female.

At the time of inclusion, participants completed five online questionnaires, including one on dietary intake. Every 6 months, 24-hour dietary records were randomly assigned to track participants' consumption of 3300 different food items over a 2-week period. Foods were classified on the basis of "the nature, extent, and purpose of the industrial processing."

Food items included mass-produced packaged breads and buns, sweet or savory packaged snacks, packaged confectionery and desserts, sodas, and sweetened drinks, meatballs, poultry and fish nuggets, and other reconstituted meat products using nonsalt preservatives such as nitrites. Instant noodles and soups, frozen or shelf-stable prepared meals, and food products containing mostly sugar, oils, and fats or hydrogenated oils, modified starches, and protein isolates were also included.

Ultraprocessed foods such as dehydrated soups, processed meats, biscuits, and sauces have a high salt content, the researchers note. Foods preserved with salt are associated with an increased risk for gastric cancer, they add.

Better understanding of the effects of food processing could lead to policies targeting product reformulation, taxation, and marketing restrictions on ultraprocessed products, the researchers suggest. Brazil and France have recommended limiting the amount of ultraprocessed food in the diet in favor of raw and minimally processed foods, the authors note.

More epidemiologic and experimental research is needed to better understand the relative effect of nutritional composition, food additives, contact materials, and other contaminants, said Touvier. Next steps for her Nutritional Epidemiology Research team include analysis of detailed nutritional information on commercial food names and brands from the NutriNet-Santé cohort data. They will focus on the impact of long-term exposure to food additives, specific substances, and exposure to multiple additives.

"Most authorized additives are probably safe, but several additives have raised some concern in animal models and deserve investigation in observational studies in humans," Touvier explained. "It's about the cocktail effect of all these additives consumed together."

Reactions to the News

This research has been widely reported in the general media in the United Kingdom, and there have been several reactions to the findings.

Scientists not involved in the study have posted comments on the Science Media Centre.

Ian Johnson, PhD, nutrition researcher and emeritus fellow, Quadram Institute Bioscience in Norwich, United Kingdom, said: "This is a very large observational study with careful and rigorous methods of data collection. The authors have identified some rather weak associations, of low statistical significance, between some types of cancer and diet. The problem is that the definition of ultra-processed foods they have used is so broad and poorly defined that it is impossible to decide exactly what, if any, causal connections have been observed."

Tom Sanders, DSC, PhD, professor emeritus of nutrition and dietetics, King's College London, said: "The approach of categorising dietary patterns that depend on industrially processed food in relation to disease risk is novel but probably needs refining before it can be translated into practical dietary advice.

"The term 'ultra-processed food' is difficult to define in terms of food quality and is not widely used by nutritional scientists," he noted. "This study appears to be focused on demonstrating that industrially processed foods increase the risk of cancer. The ultra-processed foods are focused on foods such as pot noodles, breakfast cereals, industrially processed bread, pizza, cakes, crisps, ready-to-eat desserts, meatballs and chicken nuggets, confectionery, and fizzy drinks, including those that are artificially sweetened. However, the definition excludes many homemade or artisanal foods, such as bread, cakes, biscuits, butter, meat, cheese, tinned fruit and vegetables, as well as sugar and salt used in domestic food preparation. From a nutritional standpoint, this classification seems arbitrary and based on the premise that food produced industrially has a different nutritional and chemical composition from that produced in the home or by artisans. This is not the case."

In addition, there are confounding factors, Sanders cautions. "What people eat is an expression of their lifestyle in general and may not be causatively linked to the risk of cancer. So it is necessary to rule out what are called confounding factors — things already known to cause cancer, such as smoking, obesity, alcohol intake, and low intakes of fruit and vegetables, as the accompanying editorial notes. The authors have attempted to do this with some statistical adjustments, which do not appear to alter their results. However, the high-consumers did differ in several aspects that may have contributed to the risk associated with ultra-processed food intake. For example, the participants who consumed a lot (33.3%) of these ultra-processed foods compared with those who consumed very little (about 18.7%) were more likely to be current cigarette smokers (20.2% vs 16.9%), physically inactive (24.7 vs 20.9%), and more likely to be taking oral contraceptives (30.8% vs 22.0%)."

The UK newspaper the Guardian reports the following comment from a spokesman for the Food and Drink Federation: "Processed food should not be demonised — by working closely with our partners throughout the food supply chain, we can use processing positively to ensure all sectors of society have access to safe, affordable food."

In addition, the Guardian reports the following comment from Tam Fry, spokesman for the National Obesity Forum: "A lot of research has limitations, and the scientists here are honest enough to acknowledge that theirs needs more work to be conclusive. But there is no smoke without fire: we should heed their fears — and read food labels more carefully. Huge quantities of everyday processed food have excessive levels of sugar, fat, and salt stuffed in them, and it's all listed on the packaging."

Another report by CNBC highlighted chicken nuggets and cancer in its headline, but also carried the following comments from Linda Bauld, PhD, Cancer Research UK's prevention expert: "People shouldn't worry about eating a bit of processed food here and there based on this study. There is good evidence that too little fruit, vegetables, and fiber and too much processed and red meat in our diets can contribute to the development of some types of cancer.

"Enjoying a balanced diet, avoiding junk food, and maintaining a healthy weight are things we can all do to help stack the odds in our favor," she added.

The study was funded by the Minist ère de la Sant é , the Institut de Veille Sanitaire, the Institut National de la Pr é vention et de l’Education pour la Sant é, Ré gion Ile-de-France, the Institut National de la Sant é et de la Recherche M é dicale, the Institut National de la Recherche Agronomique, the Conservatoire National des Arts et Métiers, and the Université Paris. Dr Touvier and coauthors have disclosed no relevant financial relationships. Dr LaJous has a financial relationship with AstraZeneca.

BMJ. Published on February 14, 2018. Full text, Editorial

For more from Medscape Oncology, follow us on Twitter: @MedscapeOnc


Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.