For most of the 20th century, bacteria was the enemy. Once scientists identified microorganisms as the cause of infectious disease, every effort was made to thwart these invisible invaders.
But in the last 20 years or so, scientists have developed a new respect for bacteria, and the paradigm is turning from a strategy of war, to one of co-existence. Science now considers a robust, diverse bacterial colony to be essential to good health.
In a sense, we’re actually more bacteria than human. The human body contains 10 times more bacterial cells than human cells. Nearly all of our bacteria—about three pounds—lives in our gut. Scientists call this internal bacterial colony our microbiome.
Since the introduction of the microbiome concept, it’s become common knowledge that good digestion and a strong immune system requires a healthy bacterial colony. But research now suggests that the health of your gut also has a lot to do with the health of your brain.
Clinical trials and animal models have previously shown some signs that probiotics may ease anxiety and depression. A study published May 23 in Psychiatry Research lends further support to this idea.
In the fall semester of 2014 at the College of William & Mary, students in the Introduction to Psychology class were given a questionnaire about their diet, activity level, and mental state. Researchers found that those who ate more fermented foods were less likely to suffer from social anxiety.
Regular exercise also played a role in students’ mental state, but not as much as fermented foods. The study concluded that fermented foods “may have a protective effect against social anxiety symptoms for those at higher genetic risk.” While additional research is needed, these results suggest that eating probiotic foods “may serve as a low-risk intervention for reducing social anxiety.”
Based on the emerging picture, researchers urged psychiatry and public health officials to seriously consider the impact diet has on mental health.
According to Dr. Raphael Kellman, a New York City-based physician who specializes in treating the microbiome, there are incredibly intricate interconnections between the brain and the gut. He says the microbiome not only influences our mood, but it also has a lot to do with how the brain functions and develops over time.
“The microbiome communicates with the brain through a number of mechanisms,” Kellman said. “These pathways include direct neurotransmitters that the microbiome produces. It communicates with the brain via the vagus nerve, and also via the endocrine system in the stress pathway—the hypothalamus, pituitary, and adrenal axis.”
Current treatment for neurological disorders focus on direct changes to brain chemistry, tweaking levels of neurotransmitter chemicals in hopes of tuning in the right balance. But the future of mental health treatment may focus much more on the gut than the brain, and more on food than drugs. After all, 95 percent of the body’s serotonin is produced in the intestines.
Kellman’s prescription for brain health begins with what you eat. His protocol is outlined in his book, “The Microbiome Diet.”
As diets go, Kellman’s is fairly easy to follow. It doesn’t restrict calories, protein, fat, or carbs. The hardest part is the first few weeks when foods like sugar, dairy, and gluten get shelved in an effort to heal the gut wall. But Kellman claims that people don’t typically experience cravings.
“People who go on this diet never feel like it’s really a diet,” he said. “They lose weight without the struggle. The fight is gone. It’s a much smoother path.”
Of course, Kellman’s diet strongly encourages traditionally fermented foods—such as pickles, yogurt, and sauerkraut—but it also focuses on foods and supplements with a special type of fiber called inulin.
Inulin is found in many vegetables, such as asparagus, jicama, onions, and garlic. Herbal roots, such as chicory, dandelion, and burdock, contain even higher concentrations of this fiber. Inulin supplements are usually made from Jerusalem artichokes.
You’ve heard of probiotics. Inulin is often referred to as a prebiotic. Unlike acidophilis supplements, which support a single strain of gut bacteria, inulin fiber feeds the hundreds of beneficial bacterial strains found in a healthy gut. And Kellman says it’s bacterial diversity that keeps the microbiome strong.
“An unhealthy, less diverse microbiome can contribute towards systemic inflammation,” Kellman said. “A lack of diversity can be a factor in autoimmune disorders, including lupus, arthritis, asthma, colitis, and inflammatory bowel disease.”
While most people focus on probiotics to nourish their microbiome, Kellman says prebiotics are a better bet. Individual probiotic supplements can be used to target specific issues, but prebiotic supplements are good for general gut flora wellness.
“I think most people are taking probiotics aimlessly, without a real understanding,” Kellman said. “They’re not getting a good bang for their buck. They’re better off with the prebiotics.”
Those who suffer from bloating or gas may have a microbiome with too much of one kind of microorganism. Kellman has patients with candida (a gut overgrowth of yeast) or intestinal parasites take an additional step. Herbs such as oregano and garlic help get aggressive microorganisms under control before fertilizing the colony.
A stronger microbiome means less inflammation, which means reduced risk of inflammatory brain diseases like Alzheimer’s and Parkinson’s.
When it comes to treating mood disorders, foods that strengthen the microbiome work much differently than psychotropic drugs.
“By improving the microbiome we can actually see positive changes in mood, cognitive function, and executive function,” Kellman said.
“It’s not just eliminating the poor mood—the depression or anxiety—but it’s actually creating positive emotions and a positive mood. This feeling of optimism and empowerment is quite common on the microbiome diet. You don’t see that effect with the anti-depressants.”