In recent years, probiotics have stolen the spotlight. They’re known for boosting gut bacteria, immunity, and more. Can these “friendly bacteria” do no wrong? Not necessarily. While studies show that probiotics have few side effects, most research involves short-term use. Underlying health conditions also matter.1 Probiotics affect each person differently, just like any other supplement. In some cases, probiotics can do more harm than good. Here’s what you need to know.
What Are Probiotics?
By definition, probiotics are live microorganisms that are taken for health benefits. Most are bacteria from the Lactobacillus and Bifidobacterium groups, along with yeast like Saccharomyces boulardii.2 You can find them as supplements or in fermented foods like yogurt, kefir, and miso. Their claim to fame? Gut health. Normally, good and bad bacteria live in the gut together. But when there isn’t enough good bacteria, digestive problems are likely. For instance, taking antibiotics can cause diarrhea by killing good and bacteria. Irritable bowel syndrome, constipation, and other digestive issues are also linked to microbial imbalance.
The gut is the immune system’s first line of defense.3 It’s also been found to control appetite, showing a connection to weight gain and obesity.4 Plus, through the gut-brain axis, it’s linked to emotions and cognitive function.5 Clearly, the gut is important! Probiotics restore the balance by replenishing good bacteria. Given the gut’s many roles, it’s easy to see why probiotics are so popular. Yet, like all good things, probiotics can also wreak havoc.
Side Effects Of Probiotics
1. Probiotics Can Cause Diarrhea
Probiotics are beneficial because they are alive, but it’s a different story when they die. Compared to live probiotics, inactivated microbes aren’t as efficient. They might even cause diarrhea, the very thing they’re supposed to treat. Unfortunately, it’s pretty hard to avoid dead microbes. It’s a normal result of storing commercial products. And compared to freeze-dried probiotics, the ones in dairy have a shorter shelf-life. Plus, some people might be sensitive to probiotics, making diarrhea more likely.
2. Probiotics Can Cause Drug Resistance
Probiotics can give and take genes from other microorganisms. Remember, they’re alive! This can be a problem when it comes to antibiotic-resistant genes. At first, it seems like a good thing. Shouldn’t probiotics withstand antibiotics? Isn’t that how they’ll help the gut? While this is true, they can actually build a “reservoir” of resistant genes. In the future, it can transfer those genes to other bacteria, including the bad ones. For example, Lactobacillus and Bifidobacterium are known to carry tetracycline resistant genes. Tetracycline is used to treat bacterial infections like chlamydia and urinary tract infections.
It’s possible for Lactobacillus and Bifidobacterium to “give” those genes to other bacteria, potentially creating resistant microbes in the future. While the risk is low, it’s still possible. Keep this in mind when taking probiotics.6
3. Probiotics Can Cause Endocarditis
Not all Lactobacillus bacteria have the same effect. Lactobacillus rhamnosus (L. rhamnosus) is one strain to look out for. It poses the risk of endocarditis,7 or inflammation of the heart’s inner layer.8 The chances are greater in people with weak immune systems or pre-existing heart valve problems. Granted, all strains have the potential to infect the heart, but L. rhamnosus is more likely. L. acidophilus, the most commonly known Lactobacillus bacteria, has the lowest risk.9
4. Probiotics Can Cause Sepsis
Probiotics might not be safe for people with weak immune systems. This includes elderly people, pregnant women, and babies. They’re already at high risk for disease, which probiotics may or may not help. It’s all because of their poor ability to clear out bacteria. With probiotics, the immune system does thrive, but it can also go too far. If so, there’s a possibility of sepsis,10 or an overwhelming immune reaction. This is typically in response to a bacterial infection.11
If the person is healthy yet immunocompromised, probiotics are likely fine. A doctor is the right person to weigh out the risks benefits.12
5. Probiotics Can Cause Death
Before your panic, hear us out. This side effect is linked to acute pancreatitis, or severe and sudden inflammation of the pancreas.13 The biggest concern? Infection and its complications. Therefore, probiotics seem to make sense. However, according to a study in The Lancet, probiotics don’t keep infections at bay. If anything, there is an increased risk of death.14 If you or someone you know has acute pancreatic issues, avoid probiotics at all costs.
As you can see, probiotics aren’t for everyone. It all depends on underlying conditions. To play it safe, talk to your doctor before taking probiotics.
|↑1, ↑2||The Basics of Probiotics. MedlinePlus, National Institutes of Health.|
|↑3, ↑10, ↑12||Sanders, Mary Ellen, Louis MA Akkermans, Dirk Haller, Cathy Hammerman, James T. Heimbach, Gabriele Hörmannsperger, and Geert Huys. “Safety assessment of probiotics for human use.” Gut microbes 1, no. 3 (2010): 164-185.|
|↑4||Fetissov, S. O. “Involvement of gut bacteria in appetite control.” Biologie aujourd’hui 211, no. 1 (2017): 29.|
|↑5||Carabotti, Marilia, Annunziata Scirocco, Maria Antonietta Maselli, and Carola Severi. “The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems.” Annals of gastroenterology: quarterly publication of the Hellenic Society of Gastroenterology 28, no. 2 (2015): 203.|
|↑6||Gueimonde, Miguel, Borja Sánchez, G. Clara, and Abelardo Margolles. “Antibiotic resistance in probiotic bacteria.” Frontiers in microbiology 4 (2013).|
|↑7, ↑9||Mackay, Andrew D., Mark B. Taylor, Christopher C. Kibbler, and Jeremy MT Hamilton‐Miller. “Lactobacillus endocarditis caused by a probiotic organism.” Clinical Microbiology and infection 5, no. 5 (1999): 290-292.|
|↑8||Endocarditis. U.S. National Library of Medicine.|
|↑11||Sepsis. MedlinePlus, National Institutes of Health.|
|↑13||Acute Pancreatitis. U.S. National Library of Medicine.|
|↑14||Besselink, Marc GH, Hjalmar C. van Santvoort, Erik Buskens, Marja A. Boermeester, Harry van Goor, Harro M. Timmerman, Vincent B. Nieuwenhuijs et al. “Probiotic prophylaxis in predicted severe acute pancreatitis: a randomised, double-blind, placebo-controlled trial.” The Lancet 371, no. 9613 (2008): 651-659.|