Who should not take probiotics?

It might seem odd that ingesting live microorganisms—essentially, germs—can be good for your health, but that’s the idea behind probiotics. Probiotics have become a popular supplement for people searching for better gut health and improved overall health.

But not everyone should take probiotics. They can cause unwanted side effects, such as bloating, gas, or constipation. But for some people, probiotics aren’t safe at all. Read on to find out why probiotics don’t work for everyone, what the side effects are, and who should avoid probiotics entirely.

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How do probiotics work?

Your gastrointestinal tract is home to trillions of microorganisms, including bacteria, viruses, protozoa, and fungi (including yeasts). The activity and composition of the organisms in your gut are collectively known as your gut microbiome (or microbiota or intestinal microflora). 

There is an ongoing balancing act between the beneficial and harmful bacteria in your gut, where the “good” bacteria keep the “bad” bacteria in check, which would otherwise flourish, leading to disease or infections. A healthy gut biome is crucial to your immune system and regulates proper digestion, bowel movements, and other bodily functions. If you’ve ever had a yeast infection or diarrhea after a round of antibiotics, you’ve felt the unpleasant effects of what happens when too many beneficial bacteria get wiped out.

Probiotics are beneficial microbes (or yeasts) found in fermented foods or in dietary supplements. They help to restore a healthy balance in your microbiome.

“Probiotics support the growth of healthy natural flora (good bacteria) in your body,” says Caitlin Goodwin, RN, a consultant for Mom Loves Best. “These probiotics help crucial bodily functions.” 

In addition to reducing the risk and severity of antibiotic-induced and infectious diarrhea, research shows that probiotics can reduce atopic dermatitis. They may also support your body’s overall immune function; however, research about their efficacy for immune support as well as other health benefits, such as weight management, improvement of gastric distress symptoms, and other benefits is ongoing.

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What are the side effects of probiotics?

Probiotic supplements—which contain a variety of microorganisms in powder, pills, or liquid form—are safe for most people to consume daily. However, in addition to the benefits of probiotics, some people experience mild side effects, many of which will resolve when your body’s microbiome readjusts, according to Daniel A. Monti, MD, founder of Marcus Institute of Integrative Health. Below, we detail common probiotics side effects.

1. Digestive discomfort

The most common side effect of probiotic supplementation, according to Dr. Monti, is digestive discomfort. “Some people experience bloating, gas, or digestive discomfort,” he says while adding that it is usually temporary and mild. While some studies report that probiotics alleviate constipation, it can also be a much less common side effect. 

2. Thirst

Some people experience increased thirst when they begin taking yeast probiotics, especially in the first week, as their body adjusts to the new balance in the gut bacteria. For most people, the symptoms subside on their own. If they don’t, consider changing to a bacterial probiotic rather than yeast. 

3. Headaches and migraine

Some probiotic foods, particularly fermented foods like sauerkraut and kimchi, contain high levels of biogenic amines, including histamine, tyramine, tryptamine, and phenylethylamine. These compounds may trigger headaches and migraines in some people. Biogenic amines have been found to a much lower degree in some yogurts as well. If you get a headache after eating any of the above substances, consider probiotics in supplement form. 

4. Skin reactions 

Rarely, probiotics can cause a skin rash or itchy skin. This may be due to an allergic reaction to an ingredient in the supplement and will typically go away shortly after you stop taking the supplement. If you start taking a different probiotic, begin with a small dose and be alert for any allergic reactions, Dr. Monti advises.

Who should not take probiotics?

Probiotics aren’t suitable for everyone, and in fact, they may pose too high a risk for people with certain conditions. People with the following health conditions should avoid probiotics altogether due to the rare but existing risks of taking live probiotics. 

• People with certain gastrointestinal disorders. The American Gastroenterological Association (AGA) released updated guidelines in 2020 saying that people with Crohn’s disease, irritable bowel syndrome (IBS), small intestine bacterial overgrowth (SIBO), inflammatory bowel disease (IBD), and ulcerative colitis should not take probiotic supplements as there is not enough evidence to support the use of probiotics for people with these gastrointestinal disorders.  
• People with compromised immune systems. If your immune system is compromised due to medication, chemotherapy, or radiation therapy, probiotics may increase the risk of developing a bacterial or fungal infection. 
• People with a severe illness. There is a slight risk that the microorganisms in probiotics could transfer antibiotic-resistant genes to other organisms in your digestive tract. For somebody with a potential need for antibiotic medical treatment, this could make their own gut microbiome resistant to the medicine.  
• People with food allergies. Although there is some evidence that probiotic use in newborns and infants can help decrease the likelihood of developing food allergies, some ingredients in supplements may be harmful to people who already have food allergies or an intolerance to soy, lactose, eggs, or dairy. These or other allergens can sometimes end up in probiotic formulations, even in trace amounts. Anyone with food allergies should thoroughly review the label, research the company, and consult their allergist or healthcare provider before taking probiotics.  

How to take probiotics safely

One of the best, safest ways to maintain a healthy gut microbiome is to eat fermented foods rich in probiotics.

“I recommend eating probiotic-rich foods daily as part of your personal health routine,” Dr. Monti says. “Vegetable-based probiotic foods such as living sauerkraut, natto, and kimchi happen to be rich in both prebiotics and probiotics, and, as such, they are an ideal way to incorporate probiotics into your routine.” 

In addition to consuming foods like yogurt, kombucha, sauerkraut, and kefir, you can also take probiotic supplements, which come in a variety of probiotic strains.

If you do choose to use probiotic supplements (and have cleared it with your healthcare provider or dietitian), begin with a low dosage. “Research shows that the best time of the day to take probiotics is first thing in the morning before eating breakfast or immediately before going to sleep,” Goodwin says. 

Stop taking supplements immediately if you develop a rash or any other symptoms beyond mild, temporary gastrointestinal issues. You may want to try a different bacterial strain, but only do so under the supervision of a healthcare provider who knows your medical history. 

If your gastrointestinal issues don’t go away after a couple of weeks or you develop any other symptoms, stop taking the supplements and consult your healthcare provider immediately. You may have an undiagnosed underlying condition that could influence your reaction to the probiotics. You should only continue supplementation under the guidance of medical advice.

For those with a weakened immune system, allergies, or illness, it’s crucial to consult with your healthcare provider. Together, you can weigh the benefits and risks carefully.

Your provider may recommend a strain of probiotic bacteria that is less likely to put you at risk of an adverse reaction, or they may suggest sticking with a healthy, fiber-rich diet that includes specific probiotic-rich foods that don’t pose any risk to your health.