This article was first published inÂ
Ultra-processed foods! Scarcely does a day go by without some article emerging about these dietary devils decimating our health. Indeed, just as I was trying to put the finishing touches to this article about these demons, up pops yet another study that begs for inclusion. It is forebodingly titled “Integration of lipidomics with targeted, single cell, and spatial transcriptomics defines an unresolved pro-inflammatory state in colon cancer.” That does not seem to smack of ultra-processed foods, but by the time media reports got through twisting the study, we were told that cooking oils, as commonly found in ultra-processed foods, cause cancer.
First, we had better try to get a handle on what is actually meant by “ultra-processed foods.” “Try” is the appropriate term because coming up with a simple definition is challenging. For a start, ultra-processed foods are ones that you could not recreate in your kitchen because they contain a host of ingredients such as emulsifiers, artificial flavours, colours, sweeteners, preservatives, high-fructose corn syrup, modified starch, hydrolyzed proteins, hydrogenated oils and xanthan gum, all substances that you would not find in your cupboard. They usually come packaged in plastic, which presents the added concern of trace chemicals including potential endocrine disruptors leaching into the contents. Furthermore, ultra-processed foods generally contain more fat, sugar, salt and seed oils than meals prepared at home. All these ingredients conspire to make ultra-processed foods more palatable, cheaper to produce and therefore more marketable.
What does this have to do with “lipidomics” and colon cancer? “Lipid” is the technical term for fatty substances and “lipidomics” is the study of their activity in biological systems, including cells. Lipids include the fatty acids found in corn, soybean, peanut and sunflower oils that are commonly found in the ultra-processed foods that make up more than 50% of our food supply. These fatty acids mostly fall into the category of “omega-6 fats,” with the number 6 referring to the first carbon involved in a double bond counting from the last, or “omega” carbon in the chain of carbon atoms that makes up a fatty acid. (Omega is the last letter in the Greek alphabet, hence the terminology.) By contrast, in “omega-3 fats” the first double bond is located on the third carbon from the end of the molecule. It turns out that the difference in biological activity between omega-3 and omega-6 fats is highly significant.
Cancer is initiated by a “mutation,” a change in the sequence of the nucleotides that are linked together to form DNA. Such a change can trigger the beginnings of a tumour that the immune system then recognizes as an intruder and marshals a variety of immune cells into activity. The signal for this activity comes from the release of arachidonic acid, produced in turn from linoleic acid, the most common fatty acid in seed oils. As the immune cells swing into action, they release compounds that cause inflammation, a welcome condition as the body tries to fend off the intruder. If the activity is successful, the tumour is nipped in the bud and the compounds responsible for inflammation are then eliminated by mediators produced from omega-3 fats. However, in the absence of an adequate supply of omega-3 fats, inflammation can continue to smoulder. Such chronic inflammation can damage tissues, making it easier for cancer to get a foothold.
The study reported in the “lipidomics” paper compared colon cancer tissue to normal colon tissue in the same patient. The samples were analyzed for pro-inflammatory compounds derived from omega-6 fats and inflammation resolving mediators from omega-3 fats. The normal tissue had a balance of molecules derived from both types of fat, whereas the tumour tissue had far more inflammatory compounds stemming from the omega-6 fats! The authors suggest that the problem may trace to an imbalance in the dietary intake of omega-3 and omega-6 fats due to the growing prevalence of ultra-processed foods that contain a preponderance of omega-6s. This imbalance, they propose, may be responsible for the increasing diagnosis of colorectal cancer in young people.
Not so fast! There is no data to back up this suggestion. No attempt was made to investigate the diet of the subjects in the study, so we do not know if the cancer patients were consuming more omega-6 fats. Also, the actual increase in colorectal cancer in young people is very small. Nevertheless, numerous press reports trumpeted this study as demonstrating that cooking oils cause cancer. Sheer fear-mongering.
That being said, numerous studies support the benefit of increasing the intake of omega-3 fats relative to the omega-6s. The best source of the omega-3s is fish, but nuts, ground flax seeds and chia seeds can also furnish some. Still, the most effective fix is to cut down on the foods that have the poorest ratio of omega-3s to omega-6s, namely the ultra-processed varieties.
In recent years, large epidemiological studies such as “NutriNet-Santé” in France and “Biobank” in the U.K. have followed thousands of people whose diet and health status were monitored over decades. These have linked the consumption of ultra-processed foods with heart disease, cancer, earlier mortality and even psoriasis. Other studies have implicated these foods in cognitive decline, insomnia and depression along with an increased risk of stroke and inflammatory bowel disease. True, these studies only show an association, and cannot prove a cause-and-effect relationship, but they all point in the same direction, which certainly raises concern.
Then there is the scourge of obesity. In one of the most widely quoted studies on the effects of ultra-processed foods, Dr. Kevin Hall and his team at the National Institutes of Health enlisted 20 adults who agreed to live in a clinical research unit for four weeks. They were randomly divided into two groups, one supplied with ultra-processed food and the other with a diet mainly of unprocessed foods. The diets were matched for calories, fats, proteins, sugar, sodium and fibre with subjects being told to consume as much or as little of either diet as desired. After two weeks, the groups switched to the alternate diet. The results were stunning! On the ultra-processed diet, subjects consumed about 500 calories more per day, an intake that was reflected by a weight gain of a kilogram during the ultra-processed phase. Admittedly this was a short-term study, nevertheless it adds some weight to the “beware of ultra-processed foods” argument.
So, how are we to beware? Sugary breakfast cereals, potato chips, baking mixes, instant noodles, chicken nuggets, fish sticks, frozen pizzas, soft drinks, hot dogs, fast-food burgers and fries, cold cuts, Cheezies, candy bars, flavoured yogurt, ice cream, packaged soups, energy bars, white bread, TV dinners, and even plant-based meat substitutes all fall into the ultra-processed category.
So, what then is for supper? How about home-made chicken soup with lots of vegetables, a salad of kale, tomatoes, cukes and onions with an olive oil and vinegar dressing, and pasta topped with a tomato sauce made from crushed tomatoes and flavoured with olive oil, salt and garlic? Dessert? Apple strudel. Yup! Man does not live by unprocessed food alone.
