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Woman with flu drinking from mug with probiotics for severity

Probiotic Protection Against Flu and Cold Viruses

A blend of probiotics and a prebiotic reduced the number of flu and flu-like respiratory illnesses by 75% and colds by 39% in adults.

Scientifically reviewed by:  Dr. Kathy Wilson, Ph.D, in August 2023. Written by: Jonathan Randall.

Flu can be a killer.

During the most recent flu season, nearly 43 million Americans got sick and 61,200 died.

The number of flu deaths the year before hit a staggering 79,400.1,2

Colds may seem like a nuisance, but they can also be serious. Colds can develop into pneumonia—especially in those with weakened immune systems.3

Scientists have discovered that a specific blend of probiotics can be effective at preventing flu, colds, and other respiratory infections.

In one study, this probiotic blend reduced the number of flu and flu-like respiratory illnesses by 75% and colds by 39% compared to a placebo.4

When flu and colds did occur, this same probiotic blend reduced duration and severity.4

The Dangers of Colds and Flu

Influenza affects tens of millions of people each year and kills tens of thousands in the U.S. alone.

Rates are highest during flu season, which begins in fall and lasts until spring, peaking between December and February.5

Older people, who have weaker immune systems, are particularly susceptible.

During the 2017-2018 flu season, the estimated flu-related deaths were nearly 24 times higher in people aged 65 and older than in adults 18 to 49, and over 9 times higher than in adults aged 50-64.2

Even more people suffer from colds.3 Though they generally go away in 7 to 10 days, these viral infections can lead to secondary bacterial infections like pneumonia.6

The best way to fight against these illnesses is to prevent them in the first place.

Frequent hand washing and other measures are important for prevention, but they aren’t perfect. Many people remain prone to flu and colds even after seemingly “doing everything right.”

In searching for a way to prevent these infections, scientists identified specific strains of bacteria known as probiotics.


What You Need to Know

A Probiotic-Prebiotic Blend Fights Flu and Colds

  • Winter is the peak period for transmission of flu, colds, and other upper respiratory tract infections.

  • Older adults are at the highest risk of serious complications of these illnesses, including death.

  • Probiotics, healthy microbes, help defend against infection in the digestive and respiratory tracts by stimulating immunity and boosting mucosal defense systems.

  • A select blend of five probiotic strains and a prebiotic has been shown in a randomized clinical trial to significantly reduce the number of flu cases, colds, and similar illnesses.

  • This blend also reduced the duration and severity of upper respiratory tract infections in those who did get sick.

How Probiotics Fight Colds and Flu

Flu and cold viruses strike the upper respiratory tract. These are the passageways through which air passes when we breathe, including the nasal cavity and throat.

The membrane lining these spaces and the sinuses is called the respiratory mucosa.

This delicate mucosa is prone to invasion by viruses that cause the flu, colds, and other infections (like sinusitis and sore throat).

Healthy bacteria thrive in the secretions lining the mucosa of the upper respiratory tract, just like they do in the gut.7 There, these beneficial bacteria help to fight harmful viruses and bacteria that cause disease.

The mucosal defense system is a critical immune factor that defends against invasion by disease-causing bacteria and viruses.

But the immune system, including the mucosal defense system, weakens as we age.8 This makes it easier for viruses to gain a foothold in susceptible tissues.

People with diabetes, cardiovascular disease, chronic lung disease, and other illnesses may also have weakened immune systems, putting them at even higher risk for respiratory tract infections.

Multiple studies show that a carefully chosen blend of probiotics taken orally can boost the mucosal defense, warding off the harmful viruses that cause upper respiratory tract infections like colds and flu.9-12

Most of these probiotic bacteria end up in the gut. But the mucosal defenses they strengthen favorably affect the neighboring respiratory tract as well.9,11 They also help boost general immune function.


Flu Shots and Probiotics Together

Getting a flu shot provides protection against some strains of influenza, but not others, and it does nothing for colds and other viral respiratory infections.

Flu shots often don’t work as well in older individuals, due to a decline in immune function. It is the elderly who are most at risk for flu and its complications.14

In a published meta-analysis,15 it was found that when older individuals take probiotics and prebiotics as well as get a flu shot, their chances of catching the flu are reduced.

The researchers discovered that taking the probiotics/prebiotics before vaccination increased their immune response to the vaccine.

In other words, these individuals were less likely to get the flu, due to a better immune response and increased efficacy of the vaccine than those who did not take the probiotics/prebiotics.

Another interesting point in the study was that the longer the individuals supplemented with probiotics, the better the vaccine worked in preventing the flu.

The authors concluded that ideally healthy older adults should take probiotics/prebiotics prior to their flu vaccine.

Combined Probiotic and Prebiotic Reduce Illness

Several small studies and reviews have found that probiotics are better than a placebo at reducing the number of upper respiratory tract infections, as well as the average length of illness, need for antibiotics, and work absences.10,12,13

Inspired by these findings, scientists set out to develop a select blend of probiotics and to design a placebo-controlled study to demonstrate its effectiveness.

They used a mix of five specific strains of healthy probiotic microorganisms: B. lactis BS01, L. plantarum LP01, L. plantarum LP02, L. rhamnosus LR04, and L. rhamnosus LR05.

The blend also included prebiotics called galactooligosaccharides (GOS). Prebiotics are nutrients the probiotic bacteria can digest, supporting their survival and growth.

In a study conducted over 90 days during flu season, 250 healthy, adult volunteers received either the new probiotic-prebiotic blend or a placebo daily.4

The findings were dramatic.

Compared to the placebo, the number of flu and flu-like respiratory illnesses was reduced by 75% with this probiotic-prebiotic blend. The number of colds was reduced by 39%.

While the blend couldn’t prevent all respiratory tract infections, it had clear benefits in those who did develop an illness. It led to a 37% reduction in the severity of flu symptoms and a 19% reduction in the severity of cold symptoms.

The length of these illnesses was also reduced, by about one day on average for colds, about three days for cough, and close to 1.5 days for all acute upper respiratory tract infections.

What Are Probiotics and Prebiotics?

Probiotics are healthy microorganisms that contribute to a beneficial blend of microbes in the intestines. They’re mostly various types of health-promoting bacteria.

A prebiotic is a specially chosen micronutrient that supports probiotic survival and health. In other words, it’s “food” for the probiotic organisms.

For example, galactooligosaccharides (GOS) are a specific form of prebiotic that are particularly good at supporting the growth of beneficial gut microbes.

When taken together, a blend of probiotics and a prebiotic provides the best chance for the probiotics to thrive and work optimally.



Winter and early spring see a huge increase in the incidence of flu, colds, and other upper respiratory tract infections.

Older people are particularly susceptible to respiratory tract infections because they have a lower level of immunity, and they suffer the highest rates of flu-related hospitalizations and death.

Research has found that a specific probiotic blend can boost immunity, particularly bolstering mucosal defenses in the upper respiratory tract.

A specially designed blend of five strains of probiotic bacteria, along with a potent prebiotic to support their survival, has been shown to dramatically reduce the incidence of flu, colds, and other upper respiratory tract infections.

This probiotic-prebiotic blend can also reduce the severity and duration of these illnesses when they occur.

If you have any questions on the scientific content of this article, please call a Life Extension® Wellness Specialist at 1-866-864-3027.


  1. Available at: Accessed September 4, 2019.
  2. Available at: Accessed August 22, 2019, 2019.
  3. Available at: Accessed September 4, 2019.
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  14. Smetana J, Chlibek R, Shaw J, et al. Influenza vaccination in the elderly. Hum Vaccin Immunother. 2018 Mar 4;14(3):540-9.
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