There's a universe of living organisms in your digestive tract, and the little critters can do a ton for you. Up to 100 trillion cells live in your gut microbiome, forming a world that scientists are still working to understand. 100 trillion cells -- that's enough microbes to make it the highest density natural bacterial ecosystem that we know of. Way more than your compost bin.
If all is going well, these organisms live in perfect homeostasis with you, their host. From regulating your immune system to keeping the lining of your gut strong, these organisms can be a part of how you take control of your own biology.
Just don't let them do it without your permission. When your gut bacteria are out of balance, it makes you weak, tired, and inflamed -- and it can even change your personality. It's important to know how to hack these little bastards, because they're already hacking your body for their own survival!
Here are the top things to know about your gut microbes:
Gut bacteria produce and help absorb key nutrients.
Your gut bacteria make about 75 percent of the Vitamin K that your body produces each day, with the rest coming from food. Vitamin K is a fat-soluble vitamin essential for blood coagulation and bone health.
Gut bacteria keep your tract intact
Your GI tract acts as a barrier that protects you from the outside world. If things are working the way you want, your GI tract allows nutrients in and keeps disease-causing pathogens out, at least most of the time. Gut microbes play a big role in maintaining the integrity of the gut lining and allowing this barrier system to work as it should.
As you might have read in The Bulletproof Diet, when bacteria ferment fiber (or collagen protein) in the colon, they produce short chain fatty acids. These are an important fuel for the cells that line the intestinal wall, keeping it strong and helping your body avoid leaky-gut syndrome.
The right gut bacteria also help strengthen the intestinal wall through a process that prevents the production of inflammatory TNF-α, while also increasing the amount of intestinal wall-strengthening proteins.
How the gut biome "trains" your immune system
Your ability to fight illness starts in your gut. Roughly 70 percent of your body's immune cells live in your intestines, and contact with your microbiome "programs" your immune cellsto behave in a certain way before they go out into circulation.
For example, immune cells called T cells can either suppress inflammation or promote it, depending on whether your gut is thriving or imbalanced. The microbiome begins training immune cells at birth and continues to help your developing immune system distinguish between friendly and harmful bacteria.
The early "training" can help your immune system function properly for a lifetime. On the flip side, people with diminished exposure to gut microbiota (for example, as a result of even a single antibiotic use, or from eating antibiotic-tainted non-organic meat) are more likely to develop illnesses, especially allergies and asthma. Your gut health is yet another reason to use antibiotics with caution and avoid industrially produced meat. Choose a vegetarian diet when grass-fed or wild-caught meat is unavailable.
The gut biome regulates energy balance
Gut bacteria influence how your body uses energy and whether you store that energy as fat. Depending on the makeup of your microbiome, you'll extract different amounts of energy from the food you eat. Research shows that obese people lose less energy in their feces than lean people do, due to the ability of their gut bacteria to "harvest" more energy from their diet.
In the Bulletproof Diet, you can read about how fat people have more of one species of bacteria than thin people, and how you can hack it by eating more polyphenols. This may be one mechanism that explains how Bulletproof Coffee may work in humans, but we're not sure yet. Believe it or not, there is a mouse study of butter and coffee which showed that buttered coffee helps mice have more of the "thin people bacteria" called bacteroidetes.
We also know that bacteria make a hormone called FIAF (Fasting Induced Adipose Factor) which amplifies your fat storage or fat loss, depending on how many carbohydrates your gut bacteria get from your diet, and when you eat them.
Basically, your gut microbiota has a powerful influence over genes that govern energy use and fat storage. If your gut bacteria are out of balance, these microbes will cause your body to store more fat than necessary. If you rebalance your gut, the microbes will burn fat for you all day long.
Dysbiosis: the gut microbiome out of balance
It's a delicate balance in your gut -- and almost never a perfect one. In fact, we have no idea what perfect would look like, given the extensive use of antibiotics and herbicides has forever altered the microbial landscape of our soil and our bodies.
The composition and overall health of the gut microbiome (and how it makes you feel) will shift with changes in diet, bouts of illness, periods of drinking alcohol or taking drugs, stress, body weight, age, and exposure to new environments (traveling overseas, for example).
Given the important functions of your gut microbiome, it's not hard to imagine the biological chaos that can result when things in the gut are out of balance. A significant body of research demonstrates the link between gut bacteria imbalance (dysbiosis) and many diseases common in Western society. In fact, it's tough to find a condition that's not in some way linked to gut health.
Bacterial imbalances make you weak
Since gut bacteria can be good or bad, imbalances in the types and amounts of gut microbes that cause a bunch of different problems. For example, you can find identical imbalances (greater-than-average amounts of the Firmicutes type and too little of the Bacteroidetes type) in both obese people and mice bred to be obese, and other connections to autism.
The other little problem is that a less-than-optimal balance of gut bacteria can make your body intolerant to glucose, whether you're overweight or not. High glucose can age you and makes you put on weight.
You see these imbalances in people with Type 2 Diabetes, too. Studies also show a high correlation between that the ratio of Firmicutes to Bacteroidetes in diabetics with reduced glucose tolerance, but not with BMI. In other words, gut bacteria affected glucose tolerance independent of weight. That's why you shouldn't trust those little guys in your gut or assume they're behaving themselves.
There's also leaky gut
Unhealthy bacteria in the gut don't just bring on weight and metabolic disorders. An unhealthy gut microbiome can give you leaky gut, which is just what it sounds like -- a condition where holes develop in the walls of your gut allowing intestinal contents to "leak" through into the bloodstream. This includes proteins that can trigger allergies or autoimmune disease. Bacteria and bacterial neurotoxins called lipopolysaccharides (gut researchers call it LPS because it's so common) also leak through, and they definitely don't belong in your bloodstream. Once they leak out, they can impact other organs like the liver, kidneys, and heart, causing widespread inflammation and disease. Leaky gut has been linked to many diseases including Type 1 diabetes, inflammatory bowel disease, celiac disease, multiple sclerosis, and asthma, among others. Less serious but more common issues caused by leaky gut include acne, rosacea (red skin), stomachaches, headaches, and fatigue.
Food particles -- particularly gluten, casein, and soy -- have proteins similar to proteins found in your body. When your immune system sees gluten from your leaky gut, it may accidentally begin attacking your thyroid gland in a condition called Hashimoto's. Does gluten contribute most to Hashimoto's thyroiditis, or does leaky gut? It's hard to say. Best to avoid both.
Gut bacteria also have a proven effect on your mood and are linked to neurological conditions. Bacteria leaving the gut (when they're not supposed to) can prompt or worsen a chronic inflammatory response that leads to depression. The movement of bacteria and toxins from the gut to the rest of the body is one of the most significant and preventable causes of disease in modern society.
If you're interested in learning more about your gut biome, check out the original article, which details The Bulletproof Leaky Gut Syndrome Protocol.
Photo by: NIAID