Although the immune system gets all the credit for keeping us healthy, it’s often overlooked that 70% of the immune system resides in the gut. In fact, your GI tract is the largest immune organ in the body at 30 feet long. That’s the length of a school bus or a humpback whale! Our health relies on trillions of bacteria, fungi, viruses, and other microbes, collectively called the microbiome, to aid digestion, prevent chronic inflammation, and most importantly, regulate immunity. Your microbiome is as unique to you as your fingerprint, and the more microbial diversity in your gut, the better your health. The microorganisms in your GI tract, mostly in the large intestine, help train immune cells to distinguish between helpful bacteria and harmful bacteria, allowing you to successfully fight off infections. They also optimize the absorption of nutrients from your food, especially vitamins and minerals. Dysbiosis, or an unbalanced microbiome, weakens your immune system, leading to infections, autoimmune issues, and eventually disease.
Guide to a Good Gut
If you experience digestive upset, bloating and gas, fatigue, food intolerance, skin irritations, or have an autoimmune disease, these are all signs that your gut needs help. Americans have a less diverse microbiome than people from more rural, less industrialized areas, probably due to the separation from natural environments. Plus, our exposure to ultra-processed foods containing detergent-like emulsifiers may damage the intestinal lining, leading to “leaky gut” and inflammation. Common medications like antibiotics, acid-reducers, antidepressants, and NSAIDs reduce the diversity of microbes in the gut and kill beneficial bacteria, causing long-lasting disruption to the microbiome and lowering immunity. Viral infections like COVID-19 disrupt the microbiome and allow bad bacteria to thrive in your gut. All these things are literally gut-wrenching!
You can boost your microbiome by exercising regularly, getting plenty of sleep, and eating a diet high in fiber, prebiotics and probiotics. High fiber foods include brown rice, quinoa, pears and apples with their skin on, leafy greens, broccoli and carrots. Polyphenol-rich foods like berries, green tea, and dark chocolate are also helpful. Prebiotics are non-digestible fibers that help to feed the beneficial bacteria in your gut and include onions, garlic, asparagus, leeks, and underripe bananas. Probiotics are live bacteria that can help restore balance to your microbiome, and include sauerkraut, kimchi, miso, yogurt, and kefir. Adding these gut-friendly foods to your diet is easier than you think. Instead of a post-meal dessert, I have a square of dark chocolate to appease my sweet tooth. For afternoon tea, I have green tea instead of black tea, and when eating out, I usually ask to replace pasta or white rice with broccoli or asparagus for extra fiber. Dietary supplements like turmeric and collagen also help by reducing gut inflammation and strengthening the gut lining. As if we need another reason to love dogs, there is evidence that having a dog around alters the gut microbiome in a positive way, offering protection against airway allergies and respiratory viruses.
The Gut-Brain Axis
Emerging research suggests a healthy gut is also important to your mental health due to what healthcare providers call the “gut-brain axis.” In addition to the brain in your head, you also have a second brain in your gut, and these two brains are connected by a network of nerves that send signals back and forth. This bi-directional communication allows the brain to influence intestinal activity, and the gut to influence mood, cognition, and mental health. It explains why those with mood disorders often have GI disruptions, and those with GI disorders like irritable bowel syndrome also have psychological challenges. A recent study found that those who are more resilient to stress have a microbiome that manages brain neurotransmitters differently than people prone to anxiety. Interestingly, recent findings suggest that microbes in the gut may have even played a role in the evolution of the human brain. When human/primate microbes were transplanted into mice, they boosted brain energy and learning pathways.
The Mightiest Microbes
In February, a huge global study identified a group of bacteria known as CAG-170 which were consistently found in healthy individuals across 39 different countries. These mighty microbes were depleted in those with chronic diseases like Crohn’s, Parkinson’s, and multiple sclerosis. The CAG-170 microbes produce high levels of vitamin B12 and break down dietary fibers that support other gut bacteria. Though these mighty microbes cannot be cultured in a laboratory yet, they may lead to more potent probiotics in the future to repair imbalanced microbiomes. This year researchers also released a list of 100 specific gut species – 50 “good” and 50 “bad – that serve as reliable markers for heart and metabolic health. This microbe ranking system helps to accurately predict someone’s risk for heart disease and type 2 diabetes based on their unique microbiome.
Our unique microbiome first develops while we are in the womb, becomes more diverse with a vaginal birth and the prebiotics in breast milk, and continues developing until age 2-3 years. From there a fiber-rich diet, minimizing antibiotic use, and spending time outside maintains a healthy microbiome into adulthood. It’s clear that our gut health is essential to overall health, and there is so much more that we need to learn about the microbiome. The therapeutic potential of “good” gut microbes via fecal transplantation is promising, and yes, it involves “poop sharing” from a healthy individual to one with disease – a treatment that dates back 1,000 years to ancient Chinese medicine. Instead of taking our gut for granted, we can protect it and feed it for better physical and mental health. So go with your gut!