“That gut feeling.” We’ve all experienced it, but we may have difficulty describing the sensation. We sense or “know” something internally, feeling butterflies in our stomach, almost as if our entire intestinal tract were a second brain, low on reflective skills but high on intuitive ones.
During the past decade an incredible amount of worldwide research has been devoted to understanding the role of our intestinal brain in mood disorders (like depression and anxiety) and chronic digestive disturbances (like irritable bowel syndrome, or IBS).
We know mood disorders can be helped by raising serotonin levels in the brain, whether by medications (SSRI antidepressants such as Prozac, Lexapro, and Zoloft), supplements (St. John’s wort), or lifestyle choices (quality carbs, sunlight, exercise). However, recent research has shown that both mood disorders and IBS respond to the manipulation of intestinal serotonin, which can be modulated by making sure we have healthy amounts of so-called good bacteria in our intestines.
Each of us carries approximately 100 trillion bacteria in our gut (the same number as our national debt 100 years in the future?), made up of perhaps 1,000 different species. Left to themselves, these are good bacteria, living in gentle harmony with us and with each other. They evolved over millions of years as a source of energy and nutrition for the cells that line our intestines, and they actually support our immune systems to prevent both infections and cancer.
When everything is in healthful balance, we’re fine, but when we inadvertently insert a foreigner (like salmonella or shigella) or trigger an internal ecological catastrophe by taking a broad-spectrum antibiotic, the balance gets shifted and we get sick. Fortunately, in most cases the system corrects itself promptly, but really dangerous bacteria, such as antibiotic-induced C. Difficile, can be quite stubborn to kill off.
Belly flora affect mood
Doctors are just now beginning to realize that changes in bacterial flora can directly affect our mood. Some years ago, when the wide-ranging effects of brain chemicals (neurotransmitters) were first being appreciated, researchers were surprised by how much of the brain chemical serotonin was produced in the intestines. Later, as gastroenterologists explored the whys of the endlessly puzzling IBS, they discovered that serotonin could affect both mood and intestinal motility.
An imbalance of serotonin could determine whether your IBS was constipation-dominant or diarrhea-dominant, leading some gastroenterologists to opine that if IBS patients took enough Prozac, eventually their IBS would go away. Since more than 80% of the body’s serotonin is located in the intestines, the enough became elusive, though it’s true many people with IBS do respond to SSRI antidepressants.
And now for the latest: the most recent research is showing that the presence of good bacteria in your intestines directly contributes to serotonin production. Working initially with animal models (the ubiquitous lab rat), researchers at McMaster University in Ontario discovered that a change in the dominant bacteria population in the intestines could produce visible and measurable changes in a rat’s behavior–changes such as “more cautious vs less cautious” or “passive and fearful vs active and exploring.” They report that these behavioral changes are attributable to measurable changes in serotonin.
How it plays out in humans
On a human clinical level this has very interesting possibilities. But before I go there, definite acknowledgement and praise needs to be given to all the naturopathic physicians, chiropractors, health food store clerks, persistent patients, and the nutritional supplement industry, since all have been touting the benefits of probiotics (good bacteria) to conventional physicians for decades.
I personally learned nothing about probiotics until I began working with alternative practitioners in the early 1990s. In fact, I’d had my very first taste of yogurt some years earlier while in medical school in London. Yogurt hadn’t yet achieved the status of being as widely available as it is today. I can literally see this moment in slo-mo: a very cute nursing student offering me a small spoonful from her cup. “What’s that?” I asked. She looked surprised. “You don’t have yogurt in the States? It’s made from bacteria.” “Bacteria!” My hand quickly blocked the spoon from getting any closer to my mouth. I half expected the breath coursing over her otherwise fetching nether lip to have a vaguely feculent tang.
I’d been trained to kill bacteria, not eat the stuff.
For years patients have asked their doctors if they should eat foods with live cultures, such as real yogurt (not yogurts with added sugar) and fermented vegetables like kim chee, or take probiotic supplements. They almost invariably received noncommittal shrugs. Now, after all these years, advertisements for probiotics like Align and Florastor appear in conventional medical journals. It’s been an uphill battle for the nutritional supplement industry to arrive here.
On a clinical level, we now know paying a reasonable amount of attention to your internal bacteria is important for your mood. Don’t get too obsessive about this, lying awake at night, wondering about the well-being of all 100 trillion of your fellow travelers. But if you’re prone to depression and anxiety, a daily serving of high-bacteria yogurt might be a good idea. If you’ve got either type of IBS (constipation or diarrhea dominant), do the same.
If you’re sensitive to dairy, try a super-high concentration probiotic like Ther-Biotic Complete, one capsule daily.
Or…make your own fermented foods. One of my patients made a 2012 resolution to prepare foods like these cultured vegetables and enjoy a little bit every day to bolster her intestinal flora.
And remember: since a single antibiotic dose wipes out billions of good guys, use antibiotics only when absolutely necessary. And follow every course of antibiotics with probiotics in any of the forms discussed here to restore the beneficial community in your gut.
David Edelberg MD