The first thing to know about your gut bacteria is how little we (meaning "science") actually know about what's going on down there. We know that our digestive systems are home to somewhere in the neighborhood of 500 to 1000 unique species of bacteria (although the majority of the bacteria come from a small number of these species). We also know a bit about the roles and functions of a few of these species, but very little about how they interact with each other. Despite our severely limited knowledge about these trillions of bacteria (referred to as flora) that call us home, we do know this: Gut flora are important.
In fact, there's growing evidence that just as important what what foods we put in our bodies is what our unique gut flora do with that food once it's in our gut. Healthy, vibrant people have radically different gut flora than people that are diseased or otherwise unwell. Studies have even shown that when you transport a healthy person's gut flora into the digestive system of an unhealthy person, their health improves in some ways (heard of fecal transplants?).
What Our Gut Flora Do For Us
If you want some specifics, here's a short list of the health characteristics that gut flora have been shown to influence in studies:
- Supply Critical Nutrients - When we feed our gut flora, they feed us in return. The bacteria in your digestive tract convert the parts of our food that we can't digest on our own (fiber) into a huge number of critical nutrients. Gut flora have been shown to produce amino acids, enzymes and vitamins (particularly K and the B vitamins). They also turn fiber into short chain fatty acids (like butyrate) that serve as high-quality fuel for our brains.
- Regulate Appetite and Digestion - Even more intriguing is that gut bacteria have also been shown to produce several neurotransmitters, including serotonin. We now know that our gut is a "second brain" of sorts with 100 million neurons of its own (the brain has 100 billion, fyi). This connection is pretty strongly suggestive of our gut flora influencing us on a neurological level. Indeed, it's been shown that signaling compounds produced by gut flora have a regulatory effect on appetite and digestion.
- Improve Insulin Sensitivity - Studies in mice have shown that when gut flora from an animal with good insulin sensitivity is transplanted into an animal with poor insulin sensitivity, the recipient shows improvement for this biochemical marker. Insulin is a key hormone responsible for regulating blood sugar and energy metabolism, and cellular sensitivity to insulin is critical.
- Protect Us From Food Poisoning - Most researchers in the field assume that the reason two people can consume the same contaminated food but only one will get food poisoning can be attributed to healthier gut flora in the non-poisoned person. Healthy gut flora will outcompete and minimize the threat of potentially toxic invaders like Salmonella and E. Coli.
- Improve Immune Function - Some of immune-modulating effect can be attributed to our beneficial bacteria protecting us against pathogens by outcompeting them. There is, however, a more complex mechanism at work that we're just beginning to understand. It seems that our immune systems interact with out gut and skin flora from the time we are born and is necessary for proper immune system development. Having unhealthy gut flora means some of this immune system interaction won't happen and immune function will be suppressed as a result. Indeed, researchers are now looking at unhealthy gut flora as the reason autoimmune diseases are so much more prevalent in western societies than in the developing world where antibiotics and sterilization are much less common.
The Owners Manual: Taking Care Of Your Gut Flora
I have to re-emphasize here how much this field is in it's infancy. If there's one thing microbiologists will agree on, it's how little we know about these billions of bacteria that call our guts home. To emphasize that point, it's worth pointing out that most of the information above comes from studies done only within the past 10 years.
Still, despite the limitations of our knowledge, we do still know quite a bit about how to care for our "internal ecosystem" and encourage desirable bacteria to flourish. Here's the basics:
1. Avoid Antibiotics Whenever Possible - There's no single factor contributing to the poor gut flora health of western people more than the use (and overuse) of antibiotics. Antibiotics are designed to eliminate bacterial pathogens; what do you think they do to your gut flora? When you take a course of antibiotics, it's the equivalent of dropping an atom bomb on your internal ecosystem. Not only are your gut flora less able to perform their critical functions, but you also become vulnerable to undesirable microbes. Fungal infections (like from candida, a toxic fungal parasite) are common after antibiotics for this reason. Obviously, sometimes antibiotics are necessary - but I recommend asking your doctor a lot of questions if they're being prescribed to you. Antibiotics are way too often given out for conditions for which they are completely useless in treating (viral infections, fungal infections, even some bacterial infections). If you do have to take antibiotics, it makes it that much more critical that you follow everything else on this list in the weeks and months that follow.
2. Avoid Conventional (i.e. Contaminated) Meat And Dairy - You've probably heard that giving antibiotics to livestock is a fairly common practice in conventional meat production, but do you know why? Eerily, it's not to keep them healthy, but because it is one of the most reliable ways to get a cow fat. Their gut flora get thrown out of whack and their insulin sensitivity, appetite and other weight management mechanisms get thrown off as a result. Pretty creepy, right?
This is a real issue for consumers of meat and dairy. Antibiotics will show up in low levels in the meat and milk of an animal. Consuming conventionally-produced (read; contaminated) meats on a regular basis will expose you to meaningful amounts of these commercial antibiotics and will absolutely disrupt your own gut flora. The practice is most common in beef production, but also happens in every type of conventional meat production. Eating organic meat lowers the risk, but does not eliminate it as ranchers are allowed to use antibiotics in certain instances under organic guidelines.
3. Throw Out Your Antibacterial Soap And Hand Sanitizer - First of all, I'm specifically avoiding talking about skin flora so as not to over-complicate this article, but skin flora also plays a huge role in metabolic and immune-system health. Putting antibacterials on your skin is generally not a good idea in and of itself, but the situation is worsened because these chemical antibacterials never stay exclusively on your hands. Antibacterial compounds in soaps and hand sanitizers will find their way into your body via the food or dishes you touch. As with contaminated meats, small amounts on a daily basis add up and create a meaningful effect on your gut flora. I'm not saying not to wash your hands, but 99.99% of the time regular 'ol soap is going to get the job done. No need to put these antibacterial poisons in your home and on your skin.
4. Stop Drinking Tap Water - Almost every municipality in the country adds fluoride and chlorine to their drinking water supply. Both of these are well known to disrupt gut flora. In fact, fluoride's tendency to disrupt bacteria is the reason it was put in our drinking water in the first place (fluoride disrupts the bacteria that cause cavities). My recommendation: just brush your teeth on a regular basis and drink high-quality water. The addition of fluoride/chlorine to our water is a subject that gets me pretty heated, and I've written at-length about the subject here.
As you may have guessed, fluoride toothpaste is another product I recommend against.
5. Avoid Contaminated Processed Foods - There's a long list of reasons for avoiding processed foods, but this one makes it towards the top of the list. Processed foods often contain preservatives and other chemical ingredients that, you guessed it, disrupt gut flora. Processed foods are also frequently contaminated with small amounts of industrial solvents (used to clean the machinery between batches). These industrial solvents have a number of nasty effects on our own bodies as well as our gut flora.
6. Avoid Vegetables That Get A Chlorine Wash - Some vegetables that are more prone to spoiling are treated with a chlorine bath to extend their shelf life. A lot of this chlorine stays on the food and will make its way into your gut if you eat these foods. Lettuce and baby carrots are the biggest offenders here.
7. Prebiotics - Yes PRE-biotics. When most people think of how to take care of their gut flora, they think of PRO-biotics. Probiotics are living bacteria cultures that are taken in supplement form intended to colonize your gut. Prebiotics are the specific foods we can eat that best nourish our beneficial gut bacteria. While most digestive microbiologists are skeptical of the value of probiotics (the research is inconclusive at best), they all agree on the importance of prebiotics.
So what exactly is a prebiotic? Prebiotics are components of our food that we don't break down and use ourselves, but rather are used by the bacteria in our gut. Almost everything we eat is broken down by the acids and enzymes in our stomach and quickly absorbed by the upper portions of our GI tract (the sections food moves to immediately after the stomach). Although bacteria could use these nutrients for food, they usually never get a chance to because we absorb it ourselves. There are three exceptions to this: soluble fibers, insoluble fibers and resistant starches. We lack the acids or enzymes in our stomach to break these down and they make it to our GI tract (and gut flora) intact. Specific bacteria generally specialize in consuming one of the three types of fibers, so it is important to make sure you get all three in your diet to promote a diverse and healthy gut ecosystem.
Good sources of insoluble fiber include: leafy greens (spinach, lettuce, kale, chard, etc.), bell peppers, eggplant, celery, cabbage, bok choi, brussel sprouts, cauliflower and broccoli.
Good sources of soluble fiber include: carrots, squash, potatoes, sweet potatoes, turnips, parsnips, beets, plantains, taro and yucca.
Resistant starch is the trickiest to get good amounts of, but you can find it in: plantains, uncooked potatoes, jerusalem artichokes and sushi rice.
8. Probiotics - Benefits of probiotic use have have been well documented, but interestingly it's often not quite what we would expect. For example, probiotics don't actually change the species composition of your gut. Instead, they change the genetic expression of the existing species. Why this is the case is still somewhat unclear. We do know that probiotics improve the functioning of the gut lining (epithelium). As a generalization, taking probiotics seems to be good for gut flora, just perhaps not as much as probiotics manufacturers would like us to believe.
I do, however, still take a probiotic supplement on a daily basis. The research I've done seems to show that probiotics derived from Soil Bound Organisms (SBO's) are the best choice. Unlike other probiotic products, these products will have bacterial endospores, hearty versions of the bacteria that are intended to survive times of drought. Whereas with a conventional probiotic, the majority of the bacteria will die in the acidity of the stomach, bacterial endospores are able to safely make it through the stomach and into the intestines where they are needed. SBO-derived probiotics are newer to the market and harder to find. The best brand I've come across is unquestionably Mega Sporebiotic - Spore Based Probiotic.
The Future Of Nutrition
There's no field of research in the health/nutrition world I watch with as much excitement as digestive microbiology. I say it often: research in this field over the next 5-10 years is going to revolutionize the way we think about the body-mind and how we treat disease. We'll continue to learn more about specific species and how they interact with our bodies and affect our health. One thing that the research shows conclusively at this point is that taking care of your gut flora is a critical component of promoting well-being.