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Care and Feeding of the Inflamed Brain
Have you ever heard the saying, “The way to a man’s heart is through his stomach?”
There’s probably a lot of truth to that.
But it turns out, this is not the only deep connection between feelings and food. Part 8 of my series on Food and Mood tells the tale of the gut-brain connection.
First, a little about the connection itself.
The brain and gut talk to each other and can influence each other’s actions.
The brain affects our appetite, how we digest our food, and how nutrients get delivered. The gut in turn can change brain chemistry, which can then alter our mood and our ability to handle stress and anxiety.
There’s something in the middle that facilitates all this information exchange. Actually, a lot of somethings: the trillions of microbes (like bacteria) that live in the gut. The average human has about 100 trillion of these tiny tenants, which means that they outnumber our own body cells 10 to one. [1]
The microbes talk to the brain, and the brain talks back. The language they use is multi-layered and complex, involving not just electrical signals, but also hormones, neurotransmitters, and immune chemicals called cytokines.
We now know that different emotional states, feeling stressed out for example, can directly impact the gut and its microbiome. Conversely, our gut microbes hold at least some sway over our emotions and behavior.[2]
So, researchers are now wondering, how can we take advantage of this two-way communication to improve our mental health? For example,
Can we treat emotional disturbances like depression or anxiety simply by manipulating the gut microbiome?
The short answer (based on all the research done so far) is, probably.
Now for the longer answer. Let’s break it down into two steps:
Step #1: We want to support our existing gut microbiome by eating as healthfully as we can.
This step is pretty clear-cut and backed up by research.
An unhealthy diet full of fat and sugar changes the population of microbes living in the gut, boosting the bad kind and wiping out the good kind.[3]
We’ve already learned that fat and sugar can cause inflammation. The gut microbiome helps to explain why.
An unhealthy diet can cause a condition called “leaky gut.”[4] The intestinal wall breaks apart and leaks its contents out into the rest of the body. This includes bits of bad bacteria called lipopolysaccharides, LPSs for short.
It’s these troublemakers that stimulate the release of cytokines that trigger inflammation and oxidative stress. So LPSs are bad news for both brain and body health.
They also tip the body toward weight gain and insulin resistance.[5] Packing on more fat cells will just make the inflammation problem worse, since fat cells store and release their own cytokines.[6]
Over recent decades, the developed world has shifted toward eating more sugar/refined foods, salt, and fat. This has undoubtedly contributed to the growing epidemic of obesity, inflammatory bowel disease (IBD), allergies, diabetes, autoimmune disorders, depression, and other mental disorders.
So, it just makes sense to start by cleaning up our diet by getting rid of as much pro-inflammatory stuff and adding in as much anti-inflammatory stuff as we can. This provides a solid foundation for any other nutritional steps we choose to take.
Step #2: Probiotics
The second step is potentially adding beneficial bacteria to the gut in the form of probiotics.
Probiotics are microbes that we put into our bodies by eating them in our food or taking them as supplements.
Food with live, probiotic cultures include kefir, yogurt, miso, tempeh, kimchi, and sauerkraut.
The research behind this is still in early stages, but seems promising.
In one French study, a group of healthy people who took probiotic bacteria every day for a month reported feeling less depressed, anxious, and angry, and had lower stress hormones compared to a placebo group.[7] In another study, subjects who were given a probiotic drink showed changes in brain activity in areas involved in emotional regulation.[8]
A recent review of all placebo-controlled human studies reported that taking probiotics probably can decrease anxiety and stress, and improve our mental outlook.[9] The researchers suggested that probiotics may be a useful addition or alternative to traditional antidepressant therapy, especially since some antidepressants take several weeks to work and can have significant side effects.
But there are still some unanswered questions about probiotic supplements.
For one thing, we’re still trying to work out the best dose and duration.
We’re also still trying to work out the best strains to take, although two that seem to work well are Lactobacillus and Bifidobacterium.
Another important question is, do probiotics cause side effects? None have been reported in depression/anxiety studies, but researchers caution that those with a weakened immune system or certain disorders like Crohn’s disease may be at higher risk for them.[10]
Conclusion & Action Steps
Step #1: We certainly can’t go wrong by eating a healthy, anti-inflammatory diet. We can also care for the good microbes in our gut by giving them plenty of the fiber-rich food they love, like onions, garlic, leeks, wheat, barley, oats, bananas, apples, asparagus, jicama, Jerusalem artichokes, and chicory. These foods, which feed the gut microbiome, are called prebiotics.
Step #2: Talk to your doctor and/or a licensed dietician about taking probiotic supplements.
Please keep in
mind it’s always wise to consult a licensed professional about any changes or
supplements to your diet.
[1] Reviewed in Chen, X., D’Souza, R., & Hong, S. T. (2013). The role of gut microbiota in the gut-brain axis: current challenges and perspectives. Protein & cell, 4(6), 403–414. doi:10.1007/s13238-013-3017-x
[2] Wallace, C., & Milev, R. (2017). The effects of probiotics on depressive symptoms in humans: a systematic review. Annals of general psychiatry, 16, 14.
[3] Sandhu, K. V., Sherwin, E., Schellekens, H., Stanton, C., Dinan, T. G., & Cryan, J. F. (2017). Feeding the microbiota-gut-brain axis: diet, microbiome, and neuropsychiatry. Translational Research, 179, 223-244.
[4] Cani, P. D., Neyrinck, A. M., Fava, F., Knauf, C., Burcelin, R. G., Tuohy, K. M., … & Delzenne, N. M. (2007). Selective increases of bifidobacteria in gut microflora improve high-fat-diet-induced diabetes in mice through a mechanism associated with endotoxaemia. Diabetologia, 50(11), 2374-2383.
[5] Mehta, N. N., McGillicuddy, F. C., Anderson, P. D., Hinkle, C. C., Shah, R., Pruscino, L., … Reilly, M. P. (2010). Experimental endotoxemia induces adipose inflammation and insulin resistance in humans. Diabetes, 59(1), 172–181.
[6] Agustí, A., García-Pardo, M. P., López-Almela, I., Campillo, I., Maes, M., Romaní-Pérez, M., & Sanz, Y. (2018). Interplay between the gut-brain axis, obesity and cognitive function. Frontiers in neuroscience, 12, 155.
[7] Messaoudi, M., Lalonde, R., Violle, N., Javelot, H., Desor, D., Nejdi, A., … & Cazaubiel, J. M. (2011). Assessment of psychotropic-like properties of a probiotic formulation (Lactobacillus helveticus R0052 and Bifidobacterium longum R0175) in rats and human subjects. British Journal of Nutrition, 105(5), 755-764.
[8] Tillisch, K., Labus, J., Kilpatrick, L., Jiang, Z., Stains, J., Ebrat, B., … & Mayer, E. A. (2013). Consumption of fermented milk product with probiotic modulates brain activity. Gastroenterology, 144(7), 1394-1401.
[9] Wallace, C., & Milev, R. (2017). The effects of probiotics on depressive symptoms in humans: a systematic review. Annals of general psychiatry, 16, 14.
[10] Braga, V. L., Rocha, L. P. D. S., Bernardo, D. D., Cruz, C. D. O., & Riera, R. (2017). What do Cochrane systematic reviews say about probiotics as preventive interventions?. Sao Paulo Medical Journal, 135(6), 578-586.
Dr. Pamela Coburn-Litvak has published research articles on exercise and stress in Neuroscience and Neurobiology of Learning and Behavior. Her latest book, Leaving the Shadowland of Stress, Anxiety, and Depression, was published in 2020.
After receiving a Ph.D. in Neurobiology and Behavior from the State University of New York at Stony Brook, she served as both Assistant Professor of Physiology & Pharmacology and Special Assistant to the Vice President for Research Affairs at Loma Linda University in Loma Linda, California. She then joined the Biology department at Andrews University and developed courses in human physiology as well as the neurobiology of mental illness. She also founded Rock @ Science LLC, a company that specializes in health and science education and web development. She co-developed the brain and body physiology segment of the Stress: Beyond Coping seminar with its creator, Dr. William “Skip” MacCarty, DMin.
Dr. Coburn-Litvak currently lives in California with her husband. Their two daughters are mostly grown and attending school elsewhere.
When she’s not studying or teaching about stress, she enjoys stress-relieving activities like puttering around the garden, taking nature walks with her family, knitting, cooking, and reading.
[…] The brain and the gut talk to each other constantly. And we now know that keeping our gut microbes happy is one way to keep the brain happy. This includes giving the microbes their favorite food: fiber. […]