“The complexity of things—the things within things—just seems to be endless. I mean nothing is easy, nothing is simple.” –Alice Munro
If you want to invent a new food additive, the U.S. Food and Drug Administration (FDA) requires a safety study before approval. These studies must show that the additive is healthy for humans—but it doesn’t test the effects on gut microbes. That’s a major oversight because we now know that gut microbes are enormously important for our health.
We need a new approach. Going forward, we must test additives against beneficial gut microbes to make sure we don’t kill them or—worse yet—boost any disease-causing pathogens. Some researchers are doing just that, and the results are disturbing.
A recent study by Lee-Yan Sheen and colleagues from the National Taiwan University, found that many emulsifiers, especially synthetic ones, cause changes to the gut microbiome. Emulsifiers are additives that help oil and water mix, and they create a smooth mouthfeel that manufacturers prize. They are found in a surprisingly large number of processed foods, including peanut butter, bread, sausage, and ice-cream.
The researchers found that emulsifiers helped bacteria to invade the mucus layer lining the gut. Mucus is the first line of defense we have against pathogens, so this is concerning. With the mucus compromised, microbes and their toxins find it easier to pass through the gut lining and enter the bloodstream. The researchers found evidence of systemic inflammation as a result and an uptick in metabolic disorders including increased blood sugar levels and insulin resistance.
This tracks well with an earlier study by Benoit Chassaing and colleagues at the University of Paris who found a similar effect from two synthetic emulsifiers, polysorbate 80 and carboxymethylcellulose. These two proved to be worse than other emulsifiers when it came to disrupting the gut microbiome and promoting inflammation.
Effects on the brain
As if inflammation and disease weren’t bad enough, another recent study by Ping Lei and colleagues at Tianjin Medical University found that emulsifiers could lead to cognitive decline. In particular, polysorbate 80 caused disruption of the blood-brain barrier that led to toxins building up in the brain. This study was done in mice, but the authors state that their study “provides strong evidence that dietary-induced gut microbiota dysbiosis may be a risk factor for age-related cognitive decline.”
Another study by Chassaing and colleagues found that emulsifiers affected behavior in mice. In particular, Chassaing et al. found that male mice had an exaggerated response to stress and anxiety, while female mice had reduced social behavior.
Human studies
These studies are sobering, but mice are not perfect models for people. So, it is disturbing to find similar, but more complex, results in people. A new study by Jessica Fitzpatrick and colleagues at Monash University found that while unstressed people were able to deal well with emulsifiers, stressed people showed increased intestinal permeability similar to that noted in mouse models. The study is concerning because this “leaky gut” phenomenon can increase anxiety and stress, leading to a vicious cycle.
Not all emulsifiers are bad. The synthetic ones seem to be worse, perhaps because our bodies aren’t used to them. But other emulsifiers with a long human history, like lecithin, which is found in eggs and sunflowers, seem to be well tolerated.
The upshot
The impact of emulsifiers on microbes is concerning, since beneficial microbes are essential to our good health. An unbalanced or dysbiotic gut microbiome can cause inflammation and over time can lead to many chronic diseases, including heart disease, diabetes, dementia, and cancer.
One tip is to avoid the synthetic emulsifiers polysorbate 80 and carboxymethylcellulose. A better tip is to eat more unprocessed food like veggies and fruit. In particular, you can please your gut microbes by feeding them fiber, found in beans, greens, and berries. While you’re at it, try some fermented foods like kimchi, kombucha, kefir, yogurt, and pickles. These foods contain both beneficial microbes (probiotics) and the food they like (prebiotics).
When judging food safety, we should also look at the effects on the microbiome. Emulsifiers are safe for us, but not necessarily for the tiny denizens of our gut. Foods that don’t have emulsifiers may separate, but this can be remedied by stirring or shaking them. That may be a better solution than exposing your gut microbes to danger.
