Germs That Love Diet Soda
The Germs That Love Diet Soda
There are lots of reasons to avoid processed foods. They’re often packed with sugar, fat and salt, and they tend to lack certain nutrients critical to health, like fiber. And now, new research suggests that some of the additives that extend the shelf life and improve the texture of our foods may have unintended side effect—not on our bodies directly, but on the human microbiome, the trillions of bacteria living in our guts.
These substances may selectively feed the more dangerous members of our microbial communities, causing illness and even deaths.
Consider the rise in deadly cases of clostridium difficile, or C. diff, a terrible infection of the gut. This bacterium tends to strike just after you have taken antibiotics to treat something else. Those antibiotics kill your native microbes, allowing C. diff to move in. Nearly half a million people develop the infection yearly, according to the Centers for Disease Control and Prevention, and around 29,000 die, sometimes after long bouts of painful bloody diarrhea. By one estimate, deaths linked to C. diff increased fivefold between 1999 and 2007.
One reason the bug has become more virulent is that it has evolved antibiotic resistance and is not easily treatable. But some years ago, Robert Britton, a microbiologist at Baylor College of Medicine discovered something else about C.diff: More virulent strains were outcompeting less virulent strains in the gut.
Dr. Britton and his colleagues wanted to know what gave these strains their edge, so they combed through over 200 sugars and amino acids present in the gut to see if these microbes better utilized some food source compared with others. The results of their investigation, recently published in the journal Nature, found something really strange: two of the most problematic C. diff strains have a unique ability to utilize a sugar called trehalose.
Trehalose occurs naturally in mushrooms, yeasts and shellfish, among other things. It has historically been expensive to use, but in the late 1900’s a new manufacturing process made the sugar cheap. That was good news for companies that manufactured prepackaged foods, because trehalose works great for stabilizing processed foods, keeping them moist on the shelf and improving texture. Since about 2001, we have added loads of it to everything from cookies and diet soda to beef.
Dr. Britton and his colleagues feel that we have cultivated the most toxic C. diff and caused an epidemic at hospitals. Their research shows that although C. diff was always around, they did not cause many outbreaks. Only after large quantities of trehalose entered the food supply did C. diff become so deadly.
Our gut bacteria are being bombarded with things we never ate, or never ate in the concentrations we ate before and this can lead to the spread of many new diseases, not just C. diff.
After documenting human results, Dr. Britton then redid his experiments with mice. He found that mice infected with virulent strains of C. diff that contained the sugar, trehalose, fared much worse than infected mice that were not fed the sugar. His research ads to a growing body of evidence indicating that common food additives can push our microbial communities in unhealthy directions, not only potentially aiding the emergence of new pathogens, but also encouraging diseases like obesity, diabetes and inflammatory bowel disease.
Why do we have a microbiome to begin with? Why do we lug around a few pounds of microbe in our gut? One reason is that these microbes can rapidly shift in response to new foods, helping us extract calories from a wider variety of foods than our bodies would normally allow. Think of travel to foreign countries. Sometimes our microbes do just fine with the new foods and sometimes they do not and we get sick; hence the importance of probiotics when we travel.
A good example is the microbiome of the people of Japan. They have a unique ability to break down seaweed, and scientists think it acquired this talent by borrowing DNA from microbes that live on seaweed itself. Thus by eating lots of seaweed, the ancestral Japanese pushed their microbiome to evolve until it adapted to their diet. Now their microbes could extract more calories from what they ate, better nourishing them.
But that same flexibility could be dangerous when we push our microbial community too far. Our sugary, greasy diet diverges so much from the diet humans evolved eating, I believe that the microbes of westernized populations no longer mesh well with the human body.
Gut microbes are kept slightly removed from the intestinal lining by a thin layer of mucus and the Western diet seems to erode that protective barrier, bringing microbes too close. (A diet rich in soluble fibre, on the other hand, keeps the mucus barrier thick and healthy.)
Certain food additives also lead to a weakened mucus barrier. Common emulsifiers polysorbate 80 and carboxymethylcellulose– often found in items such as mayonnaise and ice cream—prompt an erosion of the mucous barrier in mice. They also seem to cause the mice’s microbes to produce proteins that inflame the gut, increasing the animals’ tendency toward obesity and diabetes. This also happens with the food thickener, maltodextrin, which seems to both thin the mucus barrier in mice and nourish a strain of E. coli linked to Crohn’s disease, an inflammatory bowel disease. The microbiomes of patients with Crohn’s actually have an enhanced ability to break down maltodextrin compared to people without the disease, suggesting that the germs potentially driving the disease profit from the maltodextrin.
Inflammatory bowel disease has shown a huge increase in the past 20 years and it may be due to all those “sugar-free” snacks. They contain sweeteners like sucralose and saccharin, especially our diet sodas. Our bodies cannot directly digest most of these chemicals. They are meant to pass right through—but it turns out that the microbes inhabiting our colons can metabolize the sweeteners, but in a bad way that can may us ill or succumb to disease.
Scientists at the Weizmann Institute of Science in Israel have found that, in mice, saccharin causes glucose intolerance, a marker of impending diabetes—and one disease that those who eat these sweeteners are trying to avoid. When the scientists transplanted microbes from mice fed saccharin to mice that hadn’t consumed the sweetener, the recipient animals developed glucose intolerance as well, suggesting that the microbiome that was affected by the sweetener, not the sweetener itself, was causing problems.
The scientist also fed a small group of healthy people saccharin-sweetened drinks for a week. In a subset of volunteers, microbial shifts occurred, accompanied by mounting glucose intolerance. This means that diet sodas may be just as bad for your body as regular sodas.
The big question is whether food additives are worse than the high-sugar, high fat junk food they’re often a component of. Or does adding maltodextrin to your supersize ice cream really make it more harmful than it already was?
I think it’s obvious that additives cause additional damage to our bodies. North Americans have been eating junk food for decades, long before the virulent C. diff strains began causing havoc; trehalose may have tipped the scales.
Maybe hospitals should stop serving processed foods to vulnerable patients who are exposed to C. diff. Many prescription drugs contain thickeners, artificial sweeteners and stabilizers so should all these products be re-evaluated and tested again by Health Canada?
The problem is Health Canada tests individual products for their toxicity and not the long-term effect these products may have on our microbes. Science has advanced and Health Canada has not. They can test if an individual product may cause cancer but have no idea on how to determine if a product may affect our microbes and cause a disease like cancer or diabetes 10 years down the road.
What can we do in the meantime? Our microbiomes are largely shaped by the people, animals and even plants and soil you encounter. as well as the antibiotics you take and your own genetics. All these influences are hard to control, but we can control what we feed our microbes—what we eat.
We would do well to give them as much soluble fiber as possible, preferably in real food like nuts, legumes and vegetables. And we can add these concerns about thickeners, sweeteners and emulsifiers to our list of reasons to limit our consumption of processed foods. And finally we should take a high quality, high potency probiotic every day. In the same manor that we take a multiple vitamin to insure that we get all the necessary nutrients into our bodies every day, we must supplement good healthy microbiomes daily to insure our good health. [print_link]