Some studies suggest that certain probiotics may help treat stomach viruses. However, the results of these studies are inconsistent. There is still much that experts do not know about how probiotics work.

Probiotics are live microbes that are beneficial to human health. They are present in certain foods, such as kefir and live yogurt, and probiotic supplements.

There are also a large number of microbes that live in the digestive tract. Some are beneficial, while others are not. Collectively, these organisms are known as the microbiome.

The human microbiome is very complex and unique to each individual. That is why people can have different responses to different strains of probiotic, if they have any response at all.

In this article, we discuss the use of probiotics for a stomach virus, including whether they can help treat viruses, protect the microbiome, or prevent future viruses from causing infection. We also examine the possible side effects of probiotics and when to consult a doctor.

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It is unclear whether probiotics can help treat stomach viruses.

According to the National Institute of Diabetes and Digestive and Kidney Diseases, some research suggests that probiotics may help alleviate diarrhea, which can be a symptom of a stomach virus.

However, diarrhea has many potential causes other than stomach viruses. Additionally, it is not always beneficial to stop diarrhea, as it is the body’s way of getting rid of harmful substances.

Therefore, to determine whether probiotics help treat stomach viruses, it is necessary to look at how effective probiotics are at killing or otherwise inhibiting intestinal viruses. Research into this specific topic has yielded mixed results.

An older 2012 review examined evidence from previous test tube, animal, and human studies. The authors found that probiotics can be effective against intestinal viruses in children. The effectiveness in adults was less clear.

A 2020 meta-analysis also found some evidence to suggest the probiotic Saccharomyces boulardii (S. boulardii) may help treat gastroenteritis in children. After assessing 29 clinical trials, it found low to very low quality evidence that S. boulardii may offer a benefit.

However, a 2018 clinical trial involving 971 children did not find favorable results. The probiotic Lactobacillus rhamnosus did not reduce the duration or frequency of diarrhea or vomiting due to viral and bacterial infections of the digestive tract.

It may be that both the species of probiotic and the specific virus a person has play a role in determining how effective the probiotic is. However, until there are more high quality trials, much about probiotics and stomach viruses will remain unknown.

There is reason to believe that probiotics may help protect the microbiome from lasting damage after a viral infection. Specifically, it may help prevent a condition that health experts call post-infectious irritable bowel syndrome (PI-IBS).

IBS is a common condition that can cause:

Some people develop IBS after having a stomach infection. This may occur due to the toxins that some species of virus or bacteria create. Genetics, stress, and anxiety may also be risk factors.

According to an older 2014 study, gut microbiome changes are present in PI-IBS. This may mean that protecting the microbiome from damage following an infection helps prevent PI-IBS.

Older research from 2007 investigated this. The results indicate that probiotic supplements may prevent PI-IBS if a person takes them when they have a stomach virus.

The Canadian Society of Intestinal Research notes that taking a probiotic both during and after a stomach virus may help decrease damage to the gut microbiome. However, more research is necessary to prove this.

According to older research from 2008, some probiotics may help prevent gastrointestinal infections by stimulating immune function. They may also prevent the growth of pathogens, or infection-causing microbes, in the intestines.

An older 2005 study investigated the value of infant formula containing two probiotics, Bifidobacterium lactis and Lactobacillus reuteri, in preventing diarrhea. The results showed that infants who took the formula had fewer episodes of diarrhea.

There are many factors that can affect the outcome of studies on probiotics, including:

  • Study design: Many studies on probiotics are preliminary. This means they often involve a low number of participants, making it hard to determine whether the results apply to the general population. Some also do not differentiate between viral and bacterial infections or look at how probiotics are affecting the microbiome.
  • Age: Children’s microbiomes are still developing, whereas adults’ microbiomes are more stable. This may explain why some studies find using probiotics is more beneficial for children, as the probiotics may have a bigger impact on developing microbiomes.
  • Specific strains: Scientists are still learning how specific strains of bacteria and viruses affect one another. Some probiotic species may be very effective at treating certain viruses, and others may not.
  • Individuality: Everyone has a unique mix of bacteria, fungi, and viruses in their digestive tract. This unique combination of species can mean each person responds differently to probiotics.

Many healthy people can use probiotics safely. However, the National Center for Complementary and Integrative Health does not recommend using probiotics as sole treatment for a medical condition or to delay seeking medical attention, as this carries several risks.

The Food and Drug Administration (FDA) only regulates some probiotics. Any probiotic that is a general dietary supplement is not FDA regulated and therefore has not undergone testing for safety or purity.

In some cases, tests have found microbes that companies did not list on the product label in probiotic supplements. That is why if a person wants to try a probiotic supplement, they should choose a product that has undergone third-party testing.

Furthermore, scientific research on the risks of taking probiotics is lacking. While many people appear to take them with no ill effects, it is unclear how often that is the case or how often side effects do occur.

Some individuals may develop complications from probiotics. According to 2021 research, probiotics may pose additional risks to:

In rare cases, probiotics have caused widespread infections when the yeast or bacteria in the product have become opportunistic. Opportunistic pathogens are organisms that typically do not harm their host but can lead to a health condition under the right circumstances.

Also, using probiotics as a treatment for what appears to be a stomach virus could allow the symptoms to become prolonged or severe. If the symptoms do not stem from a virus, the supplement may not help at all.

If an individual suspects they or someone else has a stomach virus, and they are considering trying probiotics, they should contact a doctor for advice. The doctor will help diagnose the cause of the symptoms and make recommendations of reliable products.

A person should not take new supplements without telling a doctor first, particularly if they have a preexisting medical condition or if they are a child.

Seek immediate medical help if a person has:

  • difficulty keeping liquids down
  • vomiting longer than 2 days, or diarrhea for longer than 7 days
  • blood in their stool or vomit
  • green or yellow-green vomit
  • vomit that looks like coffee grounds
  • severe stomach cramps or pain
  • a stiff neck
  • pain looking at bright lights
  • signs of dehydration, such as dry mouth, little or no urine, or lethargy

Certain probiotics may shorten the duration of a stomach virus, reduce diarrhea, or protect the microbiome from any lasting impact the infection has.

However, research on this is still in its early stages, and the results so far are inconsistent. This makes it difficult to determine whether probiotics will have any effect, which species work best, or which may be safe.

People should not rely on probiotics as a medical treatment for stomach viruses. Instead, they should consult a doctor about the symptoms, especially if these are severe or making it hard to get enough fluids and stay hydrated.