March 2020
HAPPY GUT, HAPPY YOU
Scientists have discovered a link between the bacteria that populate your gut microbiome and mental health. Here's what to know, and what to feed those bugs to boost your mood.
At this very moment, your body is playing host to trillions of bacteria. You are, in fact, as much of a microbe as you are human, carrying around roughly the same number of bacterial cells as human ones, with nearly all the bacteria living in your gastrointestinal (GI) tract. This microbial menagerie is called the microbiome. You pick up the bacteria that colonize it early in life (through everything from traveling through the birth canal and being breastfed to not following the five second rule) and by about age 5 your gut has fully populated itself. And you've probably heard that a diverse mix of the right bacteria results in good overall health. Researchers have found connections between gut microbes and conditions ranging from allergies and heart disease to obesity and type 2 diabetes. More recently, however, scientists have identified some fascinating links between the gut microbiome and mental wellbeing.
We already know that feeling anxious affects our bellies. It makes us run to the bathroom, makes us queasy and generally makes our insides do flips like an Olympic gymnast. In fact, the gut has its own nervous system, the enteric nervous system, and it contains as many nerve cells as the spinal cord. This nervous system of the GI tract is directly connected to the brain through the vagus nerve, which acts as a sort of information super-highway. The vagus nerve connects the 2 biggest systems of your body. When you feel stressed, that's your mental state affecting your gut. The stress hormones your body secretes impact the microbes and change the way they function. While it may seem intuitive that anxiety and depression can influence the gut, the surprising thing is that the reverse is also true: the bugs in our intestinal tract also affect our mood. It turns out that our gut bacteria, including strains you may have seen on your yogurt or supplement container label, like Lactobacillus acidophilus, secrete and modulate a huge number of compounds that send signals to the brain. In other words, that super-highway runs in both directions. Most of the neurotransmitters that regulate our mood, including 50% of the dopamine and 95% of the serotonin in our bodies, are produced by microbes in the intestine, where they also influence appetite and feelings of fullness and digestion. The GI tract and brain are so intimately connected that they should actually be viewed as one system: the gut has been called your second brain.
There is evidence, for example, that people who suffer from GI distress also have higher rates of depression and anxiety. And researchers have noticed that certain species of bacteria (ones that seem to make us more melancholy) are more likely to be found in the guts of depressed patients while those linked to better mood are lacking. It's not yet known whether the specific type and balance of bugs are causing depression or if people with the condition just have a different composition of microbes, but there is a clear link between the gut and mental health. Also clear: this connection impacts us all. A growing body of research suggests that a well-balanced microbiome can improve mood even if you don't have a clinical case of depression or anxiety, helping to ease everyday stresses and keep the blues at bay. Researchers are continuing to tease out the good and bad guys of the microbe world. There is a lot more to learn: scientists discovered more than 100 new species of bacteria in 2019 alone. But there is a consensus that what you eat has a major role in determining the diversity and health of your gut bacteria.
The 2 main players are probiotics and prebiotics. Probiotic foods help populate your microbiome with beneficial bacteria, while prebiotics feed the good bugs you already have in your gut. Together, they give you a healthier overall balance of microbes. And equally important, they help crowd out the ones you don't want, so getting a regular dose of both is key to a happy microbiome. Changes in your diet can produce shifts in gut bacteria within just 24 hours. You need to maintain those eating habits, however, for the shift to last.
So, what exactly, does a gut-friendly diet look like? Many fermented foods, such as sauerkraut, yogurt, kefir and kombucha naturally contain probiotics. Look for terms like 'live and active cultures' or 'unpasteurized' on food labels to ensure the product has live bacteria. Not all do. Be wary of food or products that say they contain probiotics. Because probiotics are categorized as supplements, the FDA doesn't regulate them, so there is no assurance of the efficacy, safety or quality of the product. The preference is dosing with fermented foods rather than a pill.
Your gut bugs, like all creatures, need to eat to survive. And what the good guys crave most are prebiotics: a variety of fibers, namely oligosaccharides and cellulose. Prebiotics may be even more important than probiotics for microbiome health. You'll find them in everything from asparagus to yams. But the best sources of oligosaccharides are Jerusalem artichokes, chicory root, leeks, onions, raspberries, artichokes, beans and asparagus. Cellulose-rich foods include celery, broccoli stalks and unpeeled carrots. Aim for at least 33-39 grams of fiber from foods such as these. In fact, there is evidence that people benefit more from probiotics if they get them in conjunction with prebiotics, although we're not sure why. It's also important to minimize your intake of foods that are known to have a negative impact on good gut bacteria. Added fructose and glucose halt the production of proteins that foster the growth of these bugs.
No one is suggesting that anyone throw out their antidepressants yet. But pairing them with probiotics and prebiotics can't hurt. And focus on a plant-based diet that is as diverse as possible. So, mix it up: get your fix of fiber-rich beans, fermented pickles, yogurt and loads of bug-friendly vegetables and fruits. The wider the variety of healthy foods you eat, the greater the diversity of bacteria you'll have. And that could mean a happier microbiome and a happier you.
Beyond Mood
Changes in the microbiome, courtesy of the super-highway of chemicals that runs between the gut and brain, appear to also play a role in a variety of neurological diseases. The research is preliminary but offers hope that influencing the community of microbes in the gut could improve autism, Parkinson's disease and dementia. Read on.
Autism. While this condition is a disorder of the brain, many who suffer also have GI problems such as inflammatory bowel disease. The gut microbes of children with autism typically have fewer kinds of intestinal bacteria than those without the condition.
Parkinson's Disease. Most patients with the neurodegenerative condition experience constipation, nausea and other GI troubles. And these symptoms may occur years before the onset of motor (movement) issues and before a diagnosis. Some research suggests that the disease starts in the gut, with motor symptoms being a late development. If Parkinson's is not solely caused by changes in the brain, but instead by changes in the microbiome, then you may have to get drugs into the gut (rather than the brain) to help patients, which is much easier to do. This new concept may lead to safer therapies with fewer side effects.
Dementia. Mounting research suggests microbiome composition may also influence the onset of dementia of several types. The microbiome may influence the development of beta-amyloid plaques, but this is only one theory of how dementia-type illnesses destroy the brain. Researchers are now looking at ways of using intestinal flora to not only prevent dementia but to alleviate symptoms in those who already have it.
Gretel H. Schueller