Stress. It's something we encounter every day. People teach workshops and write books on how to deal with it. We spend countless hours and dollars trying to avoid it. But it's still there. Stress is as much a constant in our world today as the air around us. We all know that stress can have negative impacts on mental well-being, but we are just beginning to realize the effects stress can have on other bodily systems, and the effect these systems can have on our ability to deal with stress. Recent research has shown that the microbiome can be significantly affected by and play a major role in our response to stress.
The microbiome is the group of microbes (bacteria, fungi, archaea, etc.) that colonize a particular area of the body. The gut microbiome has been a population of intense research for quite a few years now. With increasing technology, we've begun to learn more and more about this population. We know that at homeostasis, each person has a specific microbial population that makes up their gut microbiome. This helps keep us healthy, keeping our digestive system running smoothly and ensuring successful processing of the food we eat. But in times of disease or stress, the microbiome in the gut can change dramatically, causing symptoms from loss of appetite to ulcers.
How exactly does stress change what's living in your intestines? It's all because of the gut-brain communications. This is achieved through neural projection pathways, neuroendocrine signaling, and entero-endocrine signaling, among other pathways. Your body uses messaging through the neurons and small chemical messengers in the form of endocrine signals to communicate over long distances, such as from the brain to the gut. In return, the gut uses the same mechanisms to send feedback to the brain. The microbes in the gut, however, can also produce chemical messages that get sent to the brain. When your body experiences stress, different chemical signals are sent to the gut; this can, in turn, cause some microbes to die and allow other microbes to take their place. The change in the composition of microbes can then change the chemical signals sent back to the brain. In this way, there is an intimate connection between the signalling input from the brain and the feedback the brain receives. These signals are essential to support mood, higher cognitive function, and behavior.
Work in animal models has highlighted the influence of stress on the gut microbiome and the subsequent influence of the microbiome on behaviors. For example, when mice are raised in a germ-free environment (no microbiome), the mice show reduced anxiety-like behaviors as compared to mice that are not raised in a germ-free environment. It has also been shown that the microbiome of the mice has an influence on the development of the amygdala, a region of the brain that plays a vital role in controlling behavioral and physiological responses to stress stimuli. The germ-free mice showed increased amygdala volume, suggesting an increased ability to handle stress. Additional studies have found that early-life stress can change an animal's microbiome for the rest of its life and that microbiome transplantation from depressed rats to healthy rats can lead to anxiety-like behaviors in the healthy rats.
All the interest in the microbiome and stress has led to new insights for the treatment of stress-related behaviors through microbiome alteration. Allowing colonization with particular species of bacteria, for example Lactoacillus helveticus and Bifdobacterium longum in both rats and humans, has been shown to reduce psychological distress. Additionally, treatment with oligosaccharides, such as fructo-oligosaccharide or galacto-oligosaccharide in mice, can have anti-depressant effects by allowing different populations of microbes to thrive on these nutrient sources.
While the microbiome still holds many mysteries, we are beginning to understand just how important its functions are in our every day lives. So the next time you're feeling stressed out, you might want to check in with your microbes and see how they're feeling. They may play a critical role in getting you through this stress and on with your life without allowing long-term health complications, like depression, anxiety disorders, or inflammatory bowel disease, to develop. The best ways to keep a healthy microbiome are to eat a healthy diet, with emphasis on fibers that support the development of beneficial bacteria, take probiotics, stay physically active, and avoid antibiotics whenever possible. Or, simply change your lifestyle to reduce your stress level. However it is achieved, a healthy microbiome can be a great advantage in the years ahead.