In today’s food-centric culture, the phrase “processed foods” gets thrown around a lot. Typically the term carries a negative undertone and sometimes for good reasons. For example, research has shown that over-consuming processed foods high in salt, sugar and fat can lead to poor health outcomes. Add “ultra” to “processed” and you get even more people talking. Such is the case with a new study from Fiolet et al., published in the British Medical Journal, which examined the relationship between ultra-processed food and cancer risk. But before you clean out your pantry or swear off sweets, let’s take a look at the strengths, limitations and applications of this research.
Key points of the study
This study assessed the associations between consumption of “ultra-processed” food and cancer risk in a population based cohort study in France. Nearly 105,000 participants at least 18 years of age were enrolled in the French NutriNet-Santé cohort, and dietary intakes were collected using repeated web-based self-administered 24-hour dietary records. These records were linked to 3,300 different food items, and the degree of processing was categorized by the NOVA classification, which has garnered some criticism in the academic community. These criticisms will be discussed later in the article.
The foods included in the study were:
Packaged breads and buns
Sweet or savory packaged snacks
Industrialized confectionery and desserts
Sodas and sweetened drinks
Meatballs, poultry and fish nuggets, and other reconstituted meat products transformed with addition of preservatives other than salt (for example, nitrites)
Instant noodles and soups; frozen or shelf-stable ready meals
Other food products made mostly or entirely from sugar, oils and fats, and other substances not commonly used in culinary preparations such as hydrogenated oils, modified starches and protein isolates
The study found that for every 10 percent increase in ultra-processed foods intake, there was an associated 12 percent increase in overall cancer risk.
What this study gets right
Scientific evidence has long established that over-consuming processed foods high in salt, sugar and fat can lead to poor health outcomes, so these new findings are not surprising. In addition, the authors of the study were vocal about the applications of the results. One of the co-authors of the study, Mathilde Touvier, stresses that it’s impossible to link ultra-processed foods to cancer risk. She also emphasizes that other studies are needed to confirm these newest results and to understand potential relationship between specific foods and cancer risk.
Putting the findings into context
As mentioned above, the definition of processed foods used in the study has received some criticism in the scientific community. Talking with the BBC, Ian Johnson, PhD, from the Quadram Institute criticized the vagueness of the term ultra-processed, stating, “The problem is that the definition of ultra-processed foods [the researchers] have used is so broad and poorly defined that it is impossible to decide exactly what, if any, causal connections have been observed.”
In the same BBC article, Tom Sanders, PhD, at King’s College London, echoes Johnson’s take. He points out that mass-produced bread would be classified as ultra-processed, but a homemade loaf or bread from a local bakery would not. Sanders says that the NOVA 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.”
By looking at the study’s confounding variables — the environmental and lifestyle characteristics that could influence the results — we can provide some additional context to these findings. For example, the study found that those with higher cancer risk were much more likely to smoke, were less active, consumed more calories overall and were more likely to be taking oral contraceptives. While the study did account for some of these variables, the authors state that their impact “cannot be entirely excluded”.
In addition, if you look at the relative risk findings from the study and put them into appropriate context, the findings become less shocking. For example, in the five year period the study was conducted, there was about 2,200 documented cases of cancer among the 105,000 participants. This is a rate of about 2.1 percent. Applying the findings that there was a 12 percent increase in overall cancer risk in individuals who ate more ultra-processed foods translates to an 0.25 percentage point increase in the cancer rate. So, the shift that the study found was an increase in overall cancer rate from 2.1 percent to 2.35 percent.
What this study gets wrong
This study postulates that some additional ingredients and chemicals such as bisphenol-A (BPA), titanium dioxide and aspartame may play a role in these findings. While consumers have the choice to purchase or avoid products with these compounds, there has been decades of scientific research behind each of them, showing that they’re safe at the levels in which we consume them.
For example, BPA has been used in food packaging for over 50 years to prevent food spoilage and foodborne illness. The U.S. Food and Drug Administration (FDA) approves all food packaging materials as “food contact substances” and has confirmed there is sufficient scientific information to demonstrate that the use of these materials is safe. FDA is not the only agency that has confirmed the safety of BPA: Organizations around the world have also reached these same conclusions.
The study also mentions titanium dioxide, a naturally occurring mineral that is processed, refined and added to a variety of foods to enhance food colors. The authors speculate that titanium dioxide may be contributing to some increased cancer rates. However, the FDA and other international agencies have concluded that titanium dioxide is safe at current consumption levels.
The study also questions the health impact of consuming “non-sugar sweeteners” — specifically referencing one study focused on aspartame. Sweeteners like aspartame are designed to assist people in efforts to reduce the amount of sugar in their diet and sugars reduction has become a public health priority. More importantly, the safety of non-sugar sweeteners is well established, with the FDA approving aspartame way back in 1981. Today aspartame is one of many non-sugar sweeteners permitted by the FDA and other health authorities around the globe. Although the authors may disagree with worldwide scientific consensus, citing one controversial study does not outweigh decades of evidence from hundreds of scientific studies supporting the safety of non-sugar sweeteners.
“Processing” these findings
Keep in mind that while some processed foods should be limited, not all processed foods are created equal. There are those that contribute key vitamins, minerals and nutrients to our diet, just as there are those that provide few benefits, if any. While avoiding or eliminating certain foods is a strategy some support, it’s our overall eating pattern that matters most. Instead of fearing foods, build an inclusive eating style that emphasizes whole grains, fruits and veggies, lean protein and unsaturated fats, regardless of if they’re processed or in their whole form.
This blog includes contributions from Kris Sollid, RD, Tamika Sims, PhD, and Allison Webster, PhD, RD.