It’s February! A month devoted to love, passion, and all matters of the heart. From a physiological perspective, our hearts play a crucial role in sustaining life, but the true “heart” of health resides someplace else, perhaps unexpected – the gut! Hippocrates knew this long ago when he declared, “All disease starts in the gut.” Twenty-five hundred years later, science is confirming what Hippocrates knew (in his gut) and it’s a fascinating time for science and gut health.
What is actually meant by “the gut”? Our digestive tract starts in our mouths, travels down our esophagus, into the stomach, small intestine, large intestine (colon), and finally the rectum. This is essentially one long tube, separated by sphincters and other muscular structures that help to propel food forward, prevent regurgitation, and essentially push waste out. When we talk about the “gut,” we’re generally referring to the small and large intestines, although sometimes the stomach is included as well.
Why focus on gut health?
Why is the gut so important? Well, the most obvious answer is that it processes the food we eat so that it can be used as fuel for our bodies, while removing toxins and waste for us to excrete. But that’s just the tip of the iceberg. Our gut has a multitude of functions, and we are learning more and more every day about how the gut interacts with other body systems to influence our health.
The major determiner of digestive health is the rainforest of bacteria that live inside our digestive tracts. We have trillions of bacterial cells in our bodies, most of which live between our mouths and our rectums. The volume of bacteria in our digestive tracts increase moving downward, so the mouth has the least amount of bacteria, and the colon has the most.
In scientific terms, the population of microorganisms that reside in our bodies is called our microbiota. Our microbiota is huge: for each human cell that we have in our body, there’s a bacterial cell to keep it company. (https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1002533) That’s a lot of bacteria! In this article, the term microbiota will refer to the environment in our guts, since that’s where a large portion of our bodies’ entire microbiota hang out. But remember that we also have abundant bacterial populations living in our mouths, nasal passages, ears, vaginas, and on our skin. We’re literally covered in – and full of – bugs!
Microbiota vs microbiome
The genetic material of all of these microorganisms is referred to as our microbiome, which is a term you may be more familiar with, and is often used interchangeably with microbiota. (We’ll use it for the remainder of this article). Studies done by the Human Microbiome Project estimate that the amount of genetic material from the microorganisms in and on our bodies is 150 times bigger than our own volume of human genetic material. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3779803/) So not only do we have a lot of bacteria cohabiting in and on us, but the bacteria is extremely diverse. This is what accounts for the high genetic load.
Why is our microbiome important?
Why does this matter? While we can’t see or feel those bacteria, they’re working really hard 24/7 to do all sort of amazing things for our bodies. Here’s a sampling of what’s on their job description:
- Immune Health: The bacteria in our guts help to “teach” special immune cells called regulatory T cells to attack foreign invaders rather than our own cells. Without this instruction, these regulatory T cells can go awry and cause issues such as colitis (https://www.ncbi.nlm.nih.gov/pubmed/21937990 ). Similarly, studies have suggested that people with less bacterial diversity have a higher incidence of autoimmune diseases. This emphasizes the importance of a healthy, diverse microbiome to keep our immune systems in check (https://www.nature.com/articles/ni0111-5)
- Mood and Brain Health:
- Special compounds called short chain fatty acids, that are produced by gut bacteria, help to strengthen the blood brain barrier. This makes it more difficult for undesirable metabolites to cross and negatively impact brain tissue. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4442490/?report=reader)
- Gut bacteria produce chemicals that influence the immune system of the nervous system to stimulate production of chemical messengers that affect mood (see article linked above).
- Specific types of bacteria actually produce neurotransmitters like GABA, norepinephrine, serotonin, dopamine, and epinephrine (https://www.ncbi.nlm.nih.gov/pubmed/22968153). This works in the other direction, too: increased levels of certain neurotransmitters like norepinephrine cause bacterial growth (https://www.ncbi.nlm.nih.gov/pubmed/14700547).
- Stress Response: Our microbiome influences how we manage the stress in our lives. In rat studies, “germ-free” rats (rats devoid of a microbiome) showed an exaggerated stress response, and this was mediated when they were colonized with specific bacterial species. (https://physoc.onlinelibrary.wiley.com/doi/full/10.1113/jphysiol.2004.063388)
- Hormone Production: Gut bacteria are capable of producing estrogen (we call this population of bacteria the estrobolome) (https://www.ncbi.nlm.nih.gov/pubmed/27107051). When there’s disruption in these bacterial populations, premenopausal women experience estrogen disruptions that increase their risk for chronic diseases (https://www.ncbi.nlm.nih.gov/pubmed/28778332). The estrobolome is also involved in other conditions, like PCOS and endometriosis. Here is a nice discussion of the impact of the estrobolome on estrogen-linked conditions like these if you’d like to read more: (https://kresserinstitute.com/gut-hormone-connection-gut-microbes-influence-estrogen-levels/)
- Metabolism: Researchers have found over 300 microbial genes associated with obesity (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2677729/?report=reader and https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2867707/?report=reader). In an often-cited mouse study, germ-free mice of the same age, gender, and size were colonized with the microbiome from either obese or lean mice, and followed over time. All mice were given the same feed in similar amounts. The mice who received the microbiome of their obese counterparts gained twice as much weight as the mice who received the lean microbiomes, suggesting that our gut bacteria has a lot to do with our metabolism and weight. (https://www.ncbi.nlm.nih.gov/pubmed/17183312 and https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3687783/?report=reader)
- Sleep: Bacterial peptides influence the intestinal cells to make messengers called cytokines that are associated with inducing REM sleep. (https://www.ncbi.nlm.nih.gov/pubmed/15245493 and https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3601973/?report=reader)
- Nutrition: A healthy microbiome increases the availability of nutrients from food (https://www.ncbi.nlm.nih.gov/pubmed/23344252). This is a perfect example of the symbiotic nature of us and our gut bugs – if we feed them well with a healthy diet (more on this below), they turn around and help us to use our vitamins.
This list is really just the tip of the iceberg of all of the functions of our microbiome. But hopefully you can appreciate the value and importance of keeping our gut bugs happy and supported.
How to have a healthy microbiome
Having a healthy microbiome isn’t as simple as just eating yogurt every once in awhile or popping a store-bought probiotic. Maintaining a healthy rainforest requires consistent effort, and can be broken down into three steps:
- Establish a healthy environment for your microbiome to thrive in. This means decreasing inflammatory foods, medications, and behaviors that contribute to altered or decreased amounts of gut bacteria. Processed foods have been associated with microbial changes that promote obesity and type 2 diabetes (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5872783/). Transition to a diet made of real, whole foods like vegetables, fruit, animal proteins (if you eat them), whole grains, legumes, and natural fats like avocados, olive oil, nuts and seeds. Reduce your sugar intake, since sugar can feed undesirable strains of bacteria and yeast. Only take antibiotics if they are very clearly indicated. Limit your use of acid-lowering medications and over the counter anti-inflammatory medications which can alter the gut microbiome and contribute to disruptions in the integrity of the gut lining.
- Feed your bugs! Just like any living organism, our gut bacteria need to be fed. And like us, they can either thrive when given the right fuel, or deteriorate when given garbage. In addition to removing processed food from your diet, add in special fibers that our gut bugs love to eat. “Prebiotics” is the term given to these fibers and they include things like raw garlic, raw leeks, raw dandelion greens, raw asparagus, raw or cooked onions, jicama, green bananas, plantains, chicory root, and jerusalem artichoke. Another strategy for feeding your gut bugs is including resistant starches in your diet. Resistant starches are starches which are – you guessed it – resistant to being digested by our small intestines, so they reach the bacteria in our large intestines intact, then those guys have a feast. Resistant starches are created by cooking and then cooling foods like potatoes, sweet potatoes, legumes, and whole grains. It’s the cooking and cooling process that makes the starches “resistant.” All the more reason to batch-cook some sweet potatoes on Sunday, and have a cooled portion with your lunch every day, all week!
- Support your rainforest. Our diets can be a fantastic source of good bacteria – small amounts of bacteria are present on/in most of the foods that we eat, but certain foods act as bacterial powerhouses and help to keep our microbial rainforests well-populated. Fermented foods are the true stars here. Lots of foods are available fermented, or you can ferment them yourselves (here’s a good resource). Fermented sauerkraut, pickles, relish, beets and other veggies are available at grocery stores and taste great. My favorite brands are Bubbies and Wild Brine but there are many others (there’s a whole section of fermented foods at Whole Foods).
Kimchi is a Korean fermented cabbage condiment that is deliciously spicy. Fermented dairy products like yogurt and kefir provide nice doses of healthy bacteria – just be sure to read labels and choose unflavored versions to avoid all of the added sugar that goes into flavored products.Kombucha is a fizzy, fermented tea drink that has gained popularity recently and is available “on tap” and by the bottle at many health food stores and grocery stores.
When we need even more bacterial support, taking a high-quality, multi-strain, potent probiotic supplement is often recommended. If you’re in the market for a probiotic, get one with at least five billion CFUs of bacteria. Make sure that the small print specifies that the dose represents the dose at time of expiration. If it doesn’t, you may be purchasing a product that had five billion CFU when it was produced, but a much smaller dose the longer it sits on the shelf. For general use, look for a probiotic that contains strains of both Lactobacillus and Bifidobacterium species.
This February, show yourself some love by supporting your microbiome. Your digestion (and your hormones, and your adrenals, and your brain, and your metabolism) will thank you!