For those who aren’t vaccinated against COVID-19, probiotics could offer a level of protection against the virus, a new study suggests.
In a randomized, placebo-controlled study led by Duke Health in North Carolina, probiotics were shown to have a "significant ability to delay a COVID infection and reduce symptoms" among people who had not been vaccinated and were exposed to the virus in their households, according to a press release.
The study was published in the journal Clinical Nutrition.
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"In patients who did not have COVID symptoms, when they started taking the probiotic, the lactobacillus probiotic we studied reduced the likelihood of getting COVID over time by 50% and reduced COVID symptoms by 50% as well," said study co-lead Paul Wischmeyer, M.D., associate vice chair for clinical research in Duke’s Department of Anesthesiology, in a statement to Fox News Digital.
This effect was seen in children and adults of all ages, he noted.
The blind study, which launched in March 2020 before vaccines were widely available, included 182 participants who were unvaccinated and had recently been exposed to someone in their household who had tested positive for COVID.
None of the participants had experienced symptoms of the virus.
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Half of them received a probiotic — lactobacillus, which is the bacteria found in yogurt, kefir and kimchi — while the other half received a placebo pill.
"This is a simple, safe probiotic we studied, specifically Culturelle, which you can buy at the store or on Amazon," Wischmeyer noted.
The participants who took the probiotic were about half as likely to have COVID symptoms or to contract the virus compared to those in the placebo group, the researchers found.
The research team was not surprised by the findings, Wischmeyer told Fox News Digital.
"There are many studies showing that probiotics can significantly reduce both the acquiring of viral infections and the severity of viral infections," he said.
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In a large study of healthy babies that was published in the journal Nature in 2017, it was shown that taking a daily lactobacillus probiotic could significantly reduce viral and other respiratory infections as well as death, the doctor pointed out.
Additional studies have shown that probiotics can reduce respiratory infections by 32% to 50% and reduce the length of respiratory and viral illness by two days or more in people who take them daily, Wischmeyer added.
The researchers do not recommend that people skip COVID vaccines in light of these findings — but suggest that probiotics could provide an added layer of protection.
"The data appears to show that taking a probiotic when you receive a vaccine should improve the vaccine’s effectiveness and make it work better, as has been shown in some initial studies," said Wischmeyer.
Probiotics are live bacteria and yeasts that are beneficial to the digestive system, according to WebMD.
Also referred to as "good" bacteria, probiotics contribute to gut health.
They can be consumed through fermented foods — including yogurt, kefir, cottage cheese, kombucha and others — and also via supplements.
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Probiotics increase the production of regulatory T-cells (white blood cells that help boost the body’s immune response), reduce inflammation, protect the lungs against infection, and express antiviral genes that help combat the COVID virus, the study found.
In addition to reducing the risk of respiratory infections, probiotics have been shown to have many other benefits, Wischmeyer told Fox News Digital.
These include improved gut health, improved immune function, reduced risk of diarrhea or gastrointestinal issues, and reduced risk for autoimmune diseases.
"There is also some data for improved weight management and improvement in depression and other brain benefits," the doctor added.
Dr. Brett Osborn, a Florida neurologist and longevity expert, was not involved in the Duke study but offered his input on the findings.
"This outcome aligns with the known anti-inflammatory properties of probiotics," he told Fox News Digital.
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COVID-19 triggers a "robust inflammatory response" that can affect the lungs, heart, brain and peripheral nervous system, Osborn pointed out.
"The induced inflammation is a critical factor in the severity of the disease, which is precisely why the first effective treatment in the early days of the pandemic was corticosteroids, potent anti-inflammatory agents," he went on. "While probiotics offer a less robust anti-inflammatory effect, they still contribute to reducing inflammation."
Reducing the body’s inflammatory response may result in less severe disease outcomes and reduced tissue damage, potentially minimizing long-term effects, the doctor added.
Dr. Marc Siegel, clinical professor of medicine at NYU Langone Medical Center and a Fox News medical contributor, who was also not involved in the Duke Health research, agreed that this was a "well-done study" with expected results.
"Probiotics have long been shown to have a positive impact in the fight against respiratory viruses," he told Fox News Digital.
"We have known for years that the gut plays a major role in COVID, and many with COVID develop GI symptoms," Siegel added. "Taking probiotics when around COVID has little downside for most, and I think it is a good idea."
The doctor did note that further research should be done into the benefits, however.
The primary limitation of the study was its small size, the researchers acknowledged.
"While limited in sample size, our study lends credence to the notion that our symbiotic microbes can be valuable partners in the fight against COVID-19 and potentially other future pandemic diseases," Wischmeyer said.
"This may be particularly relevant in under-resourced nations where vaccination rates have lagged and even in the U.S., where COVID boosters are not widely accessed."
Osborn agreed, noting, "Although the study's limited size prevented statistical significance, the results suggest a potential protective effect of probiotics in individuals infected with SARS-CoV-2."
Based on the research, Wischmeyer said the majority of people worldwide can benefit from taking a daily probiotic to reduce their risk of not only getting COVID and experiencing severe symptoms, but also the risk of getting other respiratory infections like influenza, RSV and other viruses.
"If you are taking immunosuppressive medications, you should talk to your doctor before starting a probiotic, but it may still be safe if your doctor approves," he added.
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COVID cases and hospitalizations are on the rise along with other respiratory illnesses, according to data from the Centers for Disease Control and Prevention (CDC).
Fewer than 20% of people in the U.S. have gotten the updated COVID vaccine, the agency reports.
