Is the Idea That "Everything Starts in Your Gut" Really Accurate?
At its simplest, Hippocrates' suggestion that "all disease starts in the gut" sounds like a twist on "you are what you eat," connecting the importance of a healthy diet with overall physical wellness. And while your diet plays a key role in keeping your body's systems in working order—from the leafy greens that improve brain function to lean proteins that give you energy—modern research suggests that, in a different way, the gut could play an even more powerful role in influencing the body's other systems. Ahead, we dive into the gut's connection to, well, just about everything.
It Starts with the Gut Microbiome
As a whole, says Dr. Nitin Ahuja of Penn Medicine, your gut includes all parts of the digestive tract—esophagus, stomach, small intestine, large intestine—plus the liver, gallbladder, and pancreas, which produce digestive enzymes that help break down food. But it's your gut microbiome, a collection of trillions of bacteria and microorganisms that live in the gut, that has potential connections to other parts of body while "harvesting energy from food, balancing the good versus bad bacterial composition, manufacturing neurotransmitters, such as serotonin, enzymes and vitamins like vitamin K, and [being] involved with immune and metabolic functions," according to a 2015 article in the Journal of Cardiovascular Nursing. Each person's microbiome is unique, and it can change from day to day based not only on what you're eating but on other factors—for example, if you're taking antibiotics.
Healthy Gut, Happy Life
The concept of keeping your gut healthy frequently revolves around increasing the diversity of bacteria and microorganisms in the microbiome. "Nutrition is certainly a factor in various disease states, but alongside nutrition, people are interested in the microbiome," says Dr. Ahuja. "If you have all these species of organisms in your gut, the idea is that the relative diversity of those bacteria, as well as the various metabolites produced in response to the food you're eating, may dictate how your body functions at the molecular level." But while plenty of products—from probiotics to enzyme powders—claim to improve gut health by keeping the microbiome in balance, what makes a "healthy" gut, says Dr. Ahuja, isn't so clear-cut. "The idea of restoring the gut to its original diversity, or shooting for as much balance as possible—these are abstract concepts in popular health and don't really play out in the laboratory."
The Brain-Gut Connection
If you've ever had a stomachache when you felt nervous, then the connection between your brain and gut should be obvious. But it goes both ways: The brain-gut axis, according to an article in the Annals of Gastroenterology, "consists of bidirectional communication between the central and the enteric nervous system, linking emotional and cognitive centers of the brain with peripheral intestinal functions."
Scientists are still studying ways the gut microbiome might affect the workings of the brain and other organs: Recent research has considered the relationship between the gut microbiome and Alzheimer's disease and other neurological conditions, chronic kidney disease, cancer, autism, and autoimmune diseases (among other conditions). "There's been a lot of interest in new scientific paradigms that suggest a connection between digestive function and the function of other organ systems, and in how paradigms like the microbiome might impact health and disease far outside of the gut," says Dr. Ahuja, who is hesitant to pin the responsibility for "all disease" on any one part of the body. "The science is really young and yet to be borne out of the research," he says. "For anything to start in a single organ system, it begs questions about the entire model of the body, which is systems-based—everything affects everything else."