Why ultra-processed foods are even worse for your health

A new study finds that a common food additive, ubiquitous in processed foods, changes the microbiome and the gut of healthy people

The introduction of highly processed food upon a society reliably predicts a decline in people’s health.

Highly processed food is linked to rising obesity rates and high blood pressure. A large study found a 10 percent increase in ultra-processed food was associated with a 10 percent higher risk of overall cancer and breast cancer. A study in Public Health Nutrition following 12,000 Americans with no underlying illness for more than 20 years, found that a highly processed diet is linked to a 30 percent higher chance of dying early.

Why is processed food harmful?

The convenient, flavorful, ready to eat array of processed foods are low in important nutrients: micronutrients, fiber, and the whole array of what’s in whole foods.

On the other hand they contain much of the things we try to eat less of: sugar, fat and salt.

And then, on top of that, they contain ingredients that the human intestine had never ingested until the advent of these technological innovations: Hydrogenated oils, food coloring, chemical preservatives and emulsifiers are just some of them. The nutrition label lists many ingredients foreign to human food, which up until recently came solely from nature. 

A new study in the journal Gastroenterology looks at emulsifiers – these are a hallmark of highly processed foods, added to improve texture and increase shelf life. Besides natural emulsifiers, such as lecithin, which was originally derived from egg yolk and can also be extracted from plants, there are synthetic emulsifiers such as carboxymethylcellulose (CMC) which are commonly used in industrialized foods. CMC was approved for use in the 1960s, despite no extensive testing, and was presumed to be safe because it’s poorly absorbed and is eliminated in our stool.

In the 60 years since the introduction of this emulsifier we’ve learned that even when something passes through our gut without entering our blood stream it still leaves its mark. Our gut bacteria encounter this substance and it may change the composition of the microbiome; the lining of the gut, the mucosa, which comes in contact with whatever’s just passing through, might also be susceptible.

And indeed, CMC has been shown to promote inflammation, metabolic syndrome and obesity in mice, to induce colitis – bowel inflammation – in predisposed mice, and also to change the mice’s microbiome. But that’s mice. Researchers set out to check CMC’s effect in humans.

The randomized controlled feeding study was conducted at the University of Pennsylvania, and included 16 healthy volunteers. After an 80 hour emulsifier-free diet at home, the participants were randomly assigned to an emulsifier free or one with 15 grams per day of CMC, in a residential setting in order to assure all elements of diet and exercise. 

And the results: CMC clearly changed the composition of gut bacteria, reducing select species and overall diversity, and there was a significant depletion of some of the beneficial bacterial metabolites that are known to help maintain a healthy gut.

Besides looking at fecal composition and metabolites, the researchers also performed sigmoidoscopies before and after the trial, and took biopsies of the distal colon in order to study the gut lining microscopically. In two volunteers on the CMC-containing diet, they found that bacteria were encroaching into the lining – a finding reminiscent of what you can see in people with inflammatory bowel syndrome and metabolic syndrome. This may suggest that when the health of the microbiome is compromised, or due to the CMC exposure, the altered gut bacteria start invading the lining – which when healthy is normally close to sterile.

Emulsifiers ubiquitous in processed foods

This is a small study, and just one chemical component is examined here. In real life people consume many food additives and their precise quantities are unknown. But even in this very short study there were stark changes in gut bacteria, reduction in beneficial fecal metabolites and in a few of the participants, even changes in the lining of the gut.

The authors conclude: “our observations argue that a particular food additive might perturb the host-microbiota relationship to promote disease in a subpopulation of individuals.”

So while individual susceptibility to processed foods’ ingredients may play a part, the highly processed diet is not good for anyone, for the other reasons listed above, and it’s probably one of the worst diets one can eat.

Because besides the low nutritional value, and the unnatural non-food stuff in it, it’s also built for overeating, crafted to please us and to manipulate our reward system. Food chemists design these products with a perfect sugar-fat-salt and flavor combinations, great mouthfeel, chuggability and crunch, making them so pleasing and easy to eat that they’re hard to resist or to moderate.

If there’s one small dietary commitment you want to sign on to for the coming year I suggest it’s to look more carefully at over-processed foods, and replace at least some of them with wholesome ones. A recent study in JAMA shows that two thirds of calories American kids eat now come from highly-processed foods, so we really do have our work cut out for us. 

Dr. Ayala