Benefits and drawbacks of probiotics: How much is too much?

Over a century ago, Élie Metchnikoff, the “father of probiotics” hypothesized that ingesting good bacteria, such as those found in yogurt, can have a positive impact on human health. Since then, not only has probiotic research taken off, but probiotics have become a multi-billion-dollar industry.

What are probiotics?

“Probiotics,” “prebiotics,” and “synbiotics” are terms we have all come across. These products are included in foods like yogurt, vitamins, and even skin creams. However, what is the difference between these substances and, more importantly, when should we take or avoid them?

Let's begin with a very simple differentiation. Prebiotics are plant-based foods that provide fibers and other nutrients necessary for growth of the desired “good” bacteria. They tip the balance towards beneficial bacteria over potentially harmful ones.

Probiotics, on the other hand, consist of live bacteria or other microorganisms that are meant to colonize the gut and outcompete the “bad” bacteria.

Synbiotics are a combination of prebiotics and probiotics.

We will focus specifically on probiotics.

When people generally think of bacteria, it is often in the context of harmful bugs that cause disease. However, our bodies contain a plethora of bacteria that are essential for our survival. They carry out important tasks such as aiding with food digestion, producing vitamins, and neutralizing disease-causing bacteria. If you’re wondering which organisms are found in probiotics, they are generally the same bacteria that colonize our gut. The most common ones belong to the Lactobacillus and Bifidobacterium species.

How do probiotics work?

You might be wondering how probiotics work and what effect they have on the body.

It is thought that probiotics can help create a better host microbiome environment. These organisms can do this by outcompeting harmful bacteria, oftentimes by producing chemicals that inhibit the growth of pathogenic bacteria.

Furthermore, evidence suggests that probiotics can stimulate the host immune response and allow patients to recover their microbiota after a disruptive event, such as an infection.

What are the benefits of probiotics?

Preliminary research suggests that probiotics may provide some benefit to those who suffer from irritable bowel syndrome. Similarly, there is evidence that taking probiotic supplements can prevent diarrhea that may result from infections or antibiotic regimens. This is because diarrhea, as well as antibiotic treatment, can throw off the microbe balance in the host gut.

Taking probiotics in these situations is thought to be one way to reestablish the equilibrium in the gut between “good” and “bad” bacteria. Some of the most compelling evidence in favor of probiotic supplementation comes from studies on diarrhea in children, particularly when caused by rotavirus infection. In these studies, probiotics decreased attacks of infectious diarrhea by half a day to 2 days.

Antibiotic treatments can upset the gut microbiome and its normal balance of “good” and “bad” bacteria, leading to diarrhea. Probiotics taken before, during, and after antiobiotic treatment can reduce the chances of diarrhea, according to several studies. But, researchers have had mixed results regarding the benefits of probiotics in preventing traveler’s diarrhea.

Finally, many studies have shown that probiotics may prevent infection with Clostridium difficile, as well as prevent recurrence of infection if it occurs.

Although most of the research on probiotics has been focused on patients with diseases, there is evidence to suggest that probiotic supplementation in healthy adults can lead to positive health outcomes. Researchers have found that consuming probiotics can enhance the immune response as well as benefit gastrointestinal and female reproductive health systems.

Specifically, probiotic supplementation has been shown to improve stool consistency, regularity of bowel movements, and vaginal lactobacilli concentrations. For healthy individuals, probiotics are generally considered safe. Side effects, if any, are generally mild and may include gas and other digestive symptoms.

What are the drawbacks of probiotics?

Although probiotics can have a positive impact on human health, it is important to be wary of taking probiotic supplements. This is especially true for individuals with underlying medical issues, such as those with compromised immune systems, sick infants, and those recovering from surgery. In these populations, there is evidence to suggest that taking probiotics can lead to severe side effects, including dangerous infections.

Furthermore, recent research from Washington University in St. Louis, MO, suggests that probiotics can evolve in the host gut after administration, becoming less effective and perhaps even harmful.
In this study, researchers analyzed the evolution of probiotic organisms under different stressors in laboratory mice. They found that probiotics can evolve antibiotic resistance.

They also demonstrated that these microorganisms can adapt to grow on a larger number of available sugars, which, in turn, allows them to stay in the gut longer and grow unchecked.

Alarmingly, they also showed that probiotics were able to evolve quickly and compete better with the existing gut flora, allowing them to “beat” the existing tenants and become the predominant organisms in the gut.

What's the bottom line?

It is difficult to draw a conclusion about whether probiotics are purely good or purely bad.

When taken in the correct conditions and for the correct reasons, probiotics can be very helpful and a great therapeutic tool to keep around.

However, those with underlying medical issues need to exercise greater caution when considering taking a probiotic supplement.

So, when grabbing that over-the-counter bottle of probiotics, ask yourself: Is it necessary? Do the benefits outweigh the risks?