The idea of bacteria living inside us is enough to make most people get the heebie-jeebies. Yet that’s exactly what doctors tell us is true. In recent years, more and more research has not only identified the nature of the “good bacteria” living in our bodies, but it also is beginning to illuminate the benefits of these tiny allies. The collective term for these microorganisms living in the human body is called the microbiome, and studies have shown that the health of the microbiome can be linked to overall health as well as the health of our gastrointestinal, neurological, and immune systems.  

Current estimates put the total number of healthy bacteria in the human body at upwards of 100 trillion; indeed, there are thought to be nearly three times as many of these microorganisms in an average human as there are actual human cells. The largest concentration of beneficial bacteria is in the colon and other parts of the digestive system, and it is for this reason that so much research has gone into studying how what we eat and drink can affect the microbiome. Over the last 5-10 years, one substance in particular has become popular for the potential benefits it may hold for our gut health: probiotics. 

What is the Role of the Microbiome?

To fully understand the potential benefits of probiotics, it’s helpful to also understand the gut microbiome and its role in the digestive process. As a relatively new area of research, scientists don’t yet know the full scope of what these microbiota (also known as gut flora) do for the body, but some of the benefits that have been firmly established are:   

  • Defense against pathogens: One of the ways these gut microbiota help us is by “crowding out” pathogens; in other words, by fully colonizing the digestive tract, and thus utilizing most of the substances that fuel their activities, the microbiota make it harder for pathogens or “bad bacteria” to grow. Also, some microbiota produce enzymes and compounds that seek out and destroy pathogens.  
  • Boosted immune function: The immune system often uses inflammation as a way of defending against foreign agents, but sometimes the inflammation can backfire and cause more health problems. Some microbiota can actually improve the way the immune system triggers inflammation and generally help it function more efficiently. 
  • Nutrient synthesis: Human cells can’t produce all of the nutrients the body needs to fully function, but the bacteria in the microbiome can synthesize some of these elements; examples include vitamin K, vitamin B12, and short chain fatty acids (SCFA).  
  • Gut-brain axis: One of the newest areas of research is the nature of the biochemical link between the microbiome and the central nervous system; recent studies point to microbiota having a positive effect on anxiety and depression as well as a variety of neurological conditions like autism and Parkinson’s. 

What are Probiotics?

So what exactly are probiotics? They are live microorganisms that are meant to supplement the body’s naturally occuring gut bacteria. In addition to adding to the full complement of bacteria in our digestive tract, they are meant to spur the growth and activity of those bacteria already present. The most common probiotic strains typically used are part of the Lactobacillus and Bifidobacterium groups, and various subtypes of these may have very different effects when ingested. Most probiotics are the same as or similar to the bacteria that live and grow naturally in the body. 

Many probiotics are naturally found in foods that are readily available to consumers all around the world. One of the most popular sources is yogurt and other fermented dairy products, but probiotics can also be found in fermented foods like pickled vegetables, kimchi, soy sauce, miso, tempeh, and sauerkraut; probiotics are also in beverages like kombucha and kefir. In recent years, there has been a steady rise in the availability of probiotic supplements available in pill form; each capsule contains tens of millions of select bacteria.

What Are Prebiotics and Synbiotics?  

Two other substances that are sometimes confused with probiotics are prebiotics and synbiotics. Whereas probiotics are the actual live microorganisms, prebiotics are food compounds that foster the growth or activity of microorganisms; in other words, probiotics add to the microbiome and prebiotics help the microbiome grow and function. Synbiotics, by extension, are dietary supplements that contain both probiotics and prebiotics; by combining both substances, the body can theoretically benefit from both simultaneously.

What Are the Health Benefits of Probiotics? 

With millions of Americans using probiotics, and with an estimated $32 billion global market, questions abound as to whether they even “work” or what the health benefits might be. In many ways, research on this topic is still somewhat new, so there aren’t yet definitive answers from doctors about their benefits. The studies that have been done to date show some promise, but in the words of the National Institutes for Health: “much remains to be learned about whether they’re helpful and safe for various health conditions.”

While many uses of probiotics are currently being studied, there are a few conditions where the health benefits have been demonstrated most consistently: 

  • Infectious Diarrhea: Probiotics have been shown to prevent a potential imbalance of the microbiome due to the use of antibiotics; this is most clearly seen in diarrhea associated with the Clostridium difficile bacteria.
  • Infants: Probiotics can help prevent sepsis and necrotizing enterocolitis in premature infants, and they can also help in the treatment of infant colic. 
  • Periodontal Disease: Research has shown that some probiotics may reduce disease-causing bacteria involved in periodontal disease. 
  • Ulcerative Colitis: Probiotics have been useful in fostering or maintaining remission of ulcerative colitis, a type of inflammatory bowel disease that affects millions of Americans. Some research also indicates they may help with irritable bowel syndrome (IBS) or Crohn’s disease, similar conditions that afflict the intestinal tract.  

As the antibiotic-related diarrhea example above alludes to, one of the most promising benefits of probiotic bacteria is their connection with antibiotic treatments. Antibiotics are typically prescribed by doctors to treat most kinds of bacterial infections by destroying the bacteria in question. But what often happens is that beneficial bacteria are lost at the same time as the harmful bacteria; this can lead to dangerous or unpleasant gastrointestinal side effects. Probiotics may hold the key to fostering the regrowth of the bacteria that was lost to the antibiotics. 

What Are the Risks of Probiotics? 

Even with all the potential promise of probiotic supplements, though, doctors are still unsure about which ones are specifically beneficial or how much is required to make a difference. But even in light of this uncertainty, pseudoscientific sources still make many claims about the benefits of probiotics. In time research and clinical trials may validate some of these claims, but it’s still too soon to say for sure. 

Care should be taken, however, for those who have severe illnesses or compromised immune systems. In some or even most people, a specific probiotic may be beneficial or benign. But in someone with a weakened immune system, the introduction of tens of millions of new bacteria could potentially lead to a dangerous infection.    

One other element of the probiotics question that must be taken into account is the way these substances are regulated. At the current time, probiotics can be treated as a dietary supplement, drug, or food ingredient, depending on how the manufacturer has intended it to be used; the problem with this is that the same substance could be regulated in different ways. Dietary supplements, for instance, aren’t subject to rigorous FDA approval, and they could inadvertently cause health problems for someone. 

Probiotics: The Bottom Line

Naturally occurring probiotics that are found in yogurt and other probiotic foods may have some limited benefits, and they won’t be harmful to add to your diet. Probiotic supplements, however, still require more research before much can be said about whether or not they are beneficial or harmful. If you have been considering taking probiotic supplements, it’s best to consult with a gastroenterologist to make sure you’re not at risk. If you’d like to make an appointment to discuss your digestive health, contact us at Cary Gastroenterology Associates.