How Bacteria Control Everything We Do: A Clinical Microbiologist Explains

Photo: Stocksy and mbg creative

The World Health Organization defines probiotics as "live microorganisms which, when administered in adequate amounts, confer a health benefit on the host." In short, all probiotic strains work with our body to promote health, but they don't all work the same way. Some bacteria excel at producing antimicrobial substances that protect our gut from harmful germs, others help prevent digestive upset, and some work specifically to regulate the immune system. Understanding how these different bacteria communicate with our bodies can go a long way and ensure that your probiotic is working for you.

Who runs your world? Microbes.

It may be difficult to believe, but our bodies are in constant dialogue with the microbes in our gut. Even while we sleep, our bodies are busy sampling, listening to, and taking cues from the trillions of tiny residents deep inside our intestines. And as it turns out, scientific research is discovering that these microbes (also known as the gut microbiota) have a lot to say. And what they say matters a great deal to our well-being.

In fact, ongoing research has implicated the gut microbiota in all sorts of health-related processes like nutrient uptake, defense against pathogens, production of neurotransmitters, immunomodulation, and intestinal barrier function. Even bone formation, changes in moods, and sleeping behavior are influenced by the gut microbiota

If you want to change your health, look to your microbiome.

The gut microbiota is so important to our body that some experts consider it to be a distinct, self-contained organ. But unlike other organs like the liver and brain, which are hardwired to function according to predefined genetic codes, the makeup and function of the gut microbiota is heavily influenced by environmental stimuli—especially nutrition. In other words, our gut microbiota can be influenced by lifestyle choices. And that's exciting news! It means that we have the power to ensure that the microbes talking to our bodies are on their best behavior.

We now have enough information, backed by good science, to allow each of us to take action to optimize gut health performance. First and foremost, it's important to consume a healthy diet that contains plenty of fiber-rich fruits and vegetables to promote a diverse population of microbes. The consumption of probiotics in cultured dairy products (like unsweetened yogurt and kefir) and as pill-form supplements can also play an important role.

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4 ways probiotics make you a healthier person.

Commercial probiotic strains are fully equipped to travel through the harsh environment of the stomach and small intestine and to set up shop within the large intestine. There, these microbes are well versed in communicating with our bodies. Like other members of the gut microbiota population that have a beneficial impact on health, commercial probiotic strains function broadly in the following ways:

1. Immune system support

The gastrointestinal tract is equipped with specialized cells (dendritic cells) that sample the contents of the gut to either ramp up or ramp down inflammation. Probiotics are equipped to communicate with our immune sampling cells to let them know that they are friend and not foe (i.e., toxin or invading pathogen). This interaction has a soothing effect on our immune system and is key to the beneficial effects of probiotics since inflammation has systemic and long-term consequences on our health.

2. Production of nutrients that promote health

Probiotics degrade complex carbon sources (like plant polysaccharide fiber) to produce beneficial metabolites like vitamins and short-chain fatty acids (SCFA). SCFAs such as butyrate are known to inhibit the growth of invading pathogens. They also serve as the major energy source for colonocytes (epithelial cells of the colon) and are thought to regulate human gene expression in order to reduce the risk of gastrointestinal disorders, some forms of cancer, and cardiovascular disease. Make sure to eat plenty of fiber-rich foods so that your probiotics have the fuel to generate beneficial SCFAs.

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3. Intestinal barrier protection

Probiotics strengthen the intestinal epithelial barrier so that the damaging contents of the gut remain out of our bodies. They do this by interacting with our cellular systems to fortify the intestinal epithelial mucus layer to block adhesion of pathogens and by strengthening the tight junctions between epithelial cells.

4. Inhibition of pathogen attachment to intestinal surfaces

Probiotics and other beneficial microbes are experts at manipulating their environment to keep out competitive pathogenic and harmful bacteria. Probiotics have been shown to upregulate the expression of antimicrobial products, such as defensins and cathelicidins, that our bodies make naturally. The can also tell our bodies to increase the production of pathogen-specific antibodies. Probiotics possess a powerful arsenal of their own and can produce various antimicrobials such as bacteriocins and microcins. Even the short-chain fatty acids that are produced by the probiotic fermentation of plant polysaccharides can inhibit pathogens.

Bacteria run the show, so it's important to understand them.

In my previous article, I described how each of us possesses a gut microbiota with a unique population of microbes and that our uniqueness may influence the efficacy of the probiotic supplements that we use. Today, we learned that probiotics talk to our bodies using various signaling pathways and that strains vary in their ability to manipulate these pathways to promote health. Next time I'll discuss which probiotic strains and species have demonstrated effectiveness in promoting health in areas such as antibiotic-associated diarrhea, cardiovascular health, and prevention of infections and cancer. I hope you'll stay tuned!

Remember that probiotics can offer excellent properties that promote health but that our best strategy for optimizing gut microbiota performance is a balanced and diverse diet containing prebiotic fiber and devoid of foods high in refined carbohydrates and added sugars. When considering a probiotic supplement, choose a formula that contains a diverse set of probiotic strains so that the combination of strains can work across multiple physiological pathways to improve health.

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