Are Probiotic Supplements Safe?

 Probiotic Supplements

The lining of your intestinal tract is home to trillions of bacteria. Unlike microorganisms that cause disease, many of these bacteria are friendly to your gut. The population of bacteria that live in your gut is your gut microbiome. Studies show that the composition of our microbiomes vary and are so unique that some experts call them the gut fingerprint. Research shows that the gut microbiome plays a role in digestive health and nutrient absorption but also impacts immune health since 70% of your immune system lies in your gut.

Your gut microbiome may also influence how much you weigh and how much body fat you have. Gut microbes influence weight by their impact on nutrient absorption, metabolism, and appetite. In fact, studies show that people who are obese have a gut microbiome that differs from those of lean people. Studies even show that gut microbiome composition influences brain health.

It’s not surprising that what you eat impacts your gut microbiome. Gut bacteria thrive on a diet of fermentable fiber, the type you get from certain plant-based foods, including oatmeal, artichokes, bananas, asparagus, apples, and barley. You can also boost the health of your gut microbiome by adding fermented foods to your plate, those that contain gut-friendly bacteria like Lactobacillus and Bifidobacteria. Yogurt with active cultures and fermented vegetables, like fresh sauerkraut are examples of probiotic rich foods.

For convenience, some people take a probiotic supplement instead and there’s no shortage of probiotics in pill form. As studies have revealed the benefits of probiotics, manufacturers have jumped on the bandwagon and made them available in pill form. Yet we know that when you isolate a dietary component, it can behave in the body in a different way than a food source of that component. Therefore, you might wonder whether taking a probiotic supplement is safe and effective.

Are Probiotic Supplements Safe?

A recent study discussed in the Journal of the American Medical Association raises concerns about the safety of probiotic supplements in people with a weakened immune system. For example, they point out that when doctors administered a probiotic called L. rhamnosus GG to children in an intensive care unit, just over 1% developed a bloodstream infection from that bacteria. They also discovered that the bacteria, in these ill children penetrated the lining of the gut, entered the bloodstream, and triggered a bloodborne infection. It’s likely that the stress of being hospitalized led to a leaky gut, making it possible for the probiotic bacteria to slip beyond the boundaries of the gut and enter the blood. However, other people under severe physical or mental stress could have the same problem, making a probiotic riskier. Also, people with a weakened immune system may have a higher risk of side effects when they take a probiotic.

Another concern is for individuals who have autoimmune conditions. Studies suggest that probiotics may stimulate immune system activity. That’s beneficial if you’re trying to prevent an upper respiratory infection, but it could be problematic if you already have an overactive immune system from an autoimmune condition.

And then there are the minor side effects of probiotics. Some people experience gastrointestinal upset, including gas, bloating, and nausea, when they first take a probiotic supplement. Sometimes, you can prevent this by starting with a lower dose and slowly increasing it.

Probiotic Supplements Aren’t Regulated Like Medications

Another concern is the lack of regulation of probiotics. The FDA doesn’t monitor their quality and ensure each product contains what it says it contains. Therefore, there’s no guarantee that a commercial probiotic has the number of bacteria it states on the label or that it contains any live bacteria at all. You might think you’re supplying your gut with gut-friendly bacteria, but are you? A 2016 study that tested 16 Bifidobacterium longum supplements found only one of the 16 they analyzed contained the species listed. Not only can a probiotic supplement fall short in terms of quantity of bacteria, but it may also have none of the organisms listed. Plus, there are cases where independent testing reveals bacterial species or contaminants that aren’t listed on the label.

Food Sources of Probiotics is Your Best Bet

Unless you have a medical indication for taking a probiotic or your doctor recommends it, adding more fermented foods to your diet may be the best strategy for balancing your gut microbiome. You have lots of options! Some of the best sources are yogurt with active cultures, kefir, kombucha, tempeh, and miso. You can also ferment a number of vegetables. You’re familiar with sauerkraut but you can also buy or make fermented beets, broccoli, okra, ginger, eggplant, and carrots. If you like spice, kimchi, a spicy, fermented cabbage is a tasty option. An advantage of fermented vegetables is you also get an abundance of fiber, another dietary component that builds a healthy microbiome.

The Bottom Line

While serious side effects from taking a probiotic supplement aren’t common, there are concerns that they could be harmful to people who are seriously ill and those who have autoimmune conditions. The difficulty of knowing whether a probiotic supplement is legitimate is also a concern. If you use a probiotic supplement, talk to your doctor first. Then, do your research and choose one from a reputable supplier. Also, don’t use probiotics to self-treat conditions. Get a thorough medical evaluation and diagnosis and then discuss the possibility of taking a probiotic with your health care provider.

Despite the important role the microbiome plays in health, probiotic research is still in its early stages and there’s more to learn. Until then, you can always get probiotic bacteria by enjoying an array of fermented foods.



  • Nat Rev Neurosci. 2012 Oct;13(10):701-12. doi: 10.1038/nrn3346. Epub 2012 Sep 12.
  • Nat Rev Immunol. 2017 Apr;17(4):219-232. doi: 10.1038/nri.2017.7. Epub 2017 Mar 6.
  • Journal of the American Medical Association. March 3, 2020. Volume 323, Number 9.
  • com. “The 19 Best Prebiotic Foods You Should Eat”
  • Medical News Today. “How Safe Are Probiotics?”
  • Berkeley Wellness. “Probiotics Pros and Cons”
  • National Center for Complementary and Integrative Health. “Probiotics: What You Need To Know”


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