Of Diet and Health

In her application for a Branco Weiss Fellowship some ten years ago, Suzanne Devkota suggested taking a closer look at how what we eat interacts with our intestinal bacteria. Armed with the freedom to follow her passion, she found that microbes are very sensitive to the various foods we eat, and that what we eat can affect metabolic diseases and inflammation in the body. If we adjust our diet, even slightly, in one way or another, we can change the makeup of the organisms in our intestines and thus manipulate the level of our health.

With degrees in nutritional science and metabolism, Suzanne’s research focuses on the chemical makeup of foods and how these chemicals interact with our bodies. She aims to illuminate the evolutionary development of the interrelationship between these trillions of organisms and our body. This also includes understanding the give and take of the symbiosis. In a certain way, our intestines are exposed to the outside world because they are the first to encounter what we absorb into our body. Since each individual’s diet is unique, the microbial composition of the intestinal flora is also very individual, similar to a fingerprint.

Of course, many are now eager to learn how they can improve their health by adjusting their eating habits. Suzanne says that there is only one thing that is unequivocally clear: our diet should be as varied as possible! The narrower the range of foods we eat, the narrower the community of bacteria in our gut, and the more problems we will create. Ideally, we make use of all food groups: proteins, fiber, vegetables, fruits, grains. The recipe for success is diversity.

While Suzanne was advancing the research as part of her fellowship, she realized that there is also a close connection between the intestines and the brain. Soon after, she also dealt with Alzheimer’s, Parkinson’s and other neurological diseases. George Slavich, another former Branco Weiss Fellow and today director of its alumni program, conceived a research project in which Kris Saha, yet another Branco Weiss Fellow, is also involved. Its aim is to study depression in teenagers as this diagnosis is currently increasing. Based on the knowledge that the intestines and the brain interact, George asked Suzanne to take part in the project. If possible, she should find out whether the microbiome in depressed patients differs from that in non-depressed patients. The researchers’ data collection covers an unusually broad spectrum: fMRI data provide an image of the brain and blood counts help to identify markers of inflammation. Indeed, it could be shown that there is a correlation between specific bacteria and symptoms of inflammation and depression. The percentage of these bacteria is unusually high or low in people with higher levels of inflammation markers.

Then the SARS-CoV-2 virus broke out and Suzanne and her team soon received an NIH grant to study gastrointestinal manifestations in COVID-19 patients. Even before COVID-19, a large number of published studies had shown that the prescription of antibiotics and the associated destruction of the bacterial population promoted the persistence of viruses in the body. This was particularly studied in connection with influenza, Zika and dengue. When the available niches in the gastrointestinal tract are no longer occupied because the relevant bacteria have been wiped out, these docks are available for colonization by pathogens. The SARS-CoV-2 virus binds to the ACE-2 receptor. And now we know that the highest density of these receptors is in the intestine and not in the lungs! The SARS-CoV-2 virus thus settles in the intestines and causes chronic diarrhea in many patients. Moreover, the virus can be detected in the stool, long after a patient has tested negative in the airways.

Suzanne examined hospitalized COVID-19 patients with varying degrees of severity. The doctors administered 2–12 antibiotics and antimycotics to most of these patients during their hospital stay. It is prescribed prophylactically to prevent secondary infections such as pneumonia. However, the antibiotics given can inadvertently cause problems. In the next step, more targeted antibiotic applications are to be developed in order to avoid such collateral damage.

During her Branco Weiss Fellowship, Suzanne had the idea that bacteria from the intestines could also get into other parts of the body where they actually don’t belong and therefore cause inflammation. She soon discovered that intestinal bacteria can migrate into the fat tissue of Crohn’s disease patients, where they trigger a phenomenon called “creeping fat”, or fat expansion around the intestines. This could potentially be a similar mechanism in obesity. The task now is to find out why certain bacteria translocate while others do not. The ultimate goal is to keep the bacteria where they belong and to make sure that they don’t go anywhere else.

Another promising topic of ongoing research is phage therapy. Phages are viruses that target bacteria – each of them a different, specific bacterium. At some point, bacteriophages could presumably be administered, which then attack certain bacteria while leaving the rest of the microbiome untouched.

Suzanne’s hypothesis from the early days of her fellowship, according to which intestinal bacteria are biosensors for our external environment, has therefore been verified in many ways. Since every person is different, we each have to listen to our own body in order to be able to say what works for us and what doesn’t. When we start paying more attention to our intestinal tract, we will see that it is a sensitive sensor that can show the first signs of problems in our body. A number of diseases – including cancer – could soon be detected much earlier than before. The trend towards personalized medicine is completely justified.