Probiotics for Winter Immunity

Kerry Beeson BSc (Nut. Med.) Nutritional Therapist

The immune system: what actually is it?

Put simply: the immune system is a network of different cells, tissues, organs and proteins which are located throughout the body. The different components of the immune system all work together to protect us against threats like physical injuries, toxins, pathogens and even stress.

But did you know that 70% of your entire immune system is based in your gut?

This means that in order to improve our immunity, it is vital to support and maintain good gut health. With that in mind, this article looks at a new way to approach cold and flu season, starting from the inside out.

How could probiotics and good bacteria support my immune system?

woman at a window
Ticking off all the ways to keep your gut in good shape can be tough. Probiotics are a quick win!

Good health starts in the gut

Having learnt that 70% of our immune system resides in the gut, let’s take a closer look at the fascinating internal world of our intestines to find out what this really means.

Inside everybody’s gut is a multitude of tiny micro-organisms, collectively known as the microbiome. Ideally, the microbiome should be comprised mostly of good, or ‘friendly’, bacteria, commonly known as probiotics. However, we can easily tolerate a small percentage of the ‘bad guys’, so long as they are kept in check by our friendly bacteria. Our friendly bacteria colonies actively prevent pathogens from overgrowing by competing with them for space and nutrients. They even produce different acids to lower the pH of our gut, making it unfavourable for pathogens to live there.

So how do we make sure our microbiome stays healthy? There are lots of ways to naturally increase your levels of good bacteria and optimise your gut health. Increasing your fibre intake, decreasing sugar consumption and getting a good night’s sleep are all great options. However, modern life doesn’t always allow us to squeeze all these healthy routines into our day. This is where taking good quality probiotic supplements can help. They are designed to keep the gut microbiome healthy in a way that is easy to fit into daily life.

How do probiotics help support your immune system?

During the winter months we often get asked ‘do probiotics help fight colds?’, so let’s take a look at the potential benefits of probiotics for immunity.

Good gut bacteria have many important jobs, including, providing the first line of defence against ingested pathogens (‘the bad guys’, such as undesirable bacteria and viruses); preventing bad bacteria from sticking to the gut lining, and strengthening the delicate intestinal wall. But what most people don’t know is that our friendly bacteria colonies also ‘talk’ to the immune system, helping to enhance our immune responses1 and keep us healthy. Healthcare professionals can head over to the Professionals site to learn more about probiotics and immunity.

This means that if our good gut bacteria aren’t fighting fit then we may be more at risk for picking up infections such as colds and flu. These nasty ‘bugs’ can be difficult to avoid, as we come into contact with them everywhere we go – in the office, at school/college, on public transport and even at home, from other family members. Topping up your friendly bacteria with a probiotic supplement offers an extra level of support throughout the cold and flu season, and can be an invaluable investment in your health.

Do remember though that there is no ‘one size fits all’ when it comes to probiotics. It’s important to pick the right strains (types) for you, for example probiotics for men, probiotics for women or probiotics for kids. Furthermore, people that are immune-suppressed or who have weakened immune systems should speak to their doctor before taking probiotics. This is due to their interaction with the immune system.

Finding the best probiotic to boost my immune system

Probiotics come in lots of different shapes and sizes: yoghurts, fermented drinks (like kombucha) and, most recently, supplements. With 1 in 3 Brits now taking a daily nutritional supplement2, the probiotics industry is growing rapidly. With so many to choose from, it can be difficult to find the one to best suit your needs.

Perhaps the most important thing to remember here is that different probiotics supplements do different things, depending on the strains of probiotic bacteria used in them. Revolutionary research is being conducted all the time to figure out which probiotic strains possess which health benefits. Scientists are particularly keen to understand which strains help to support our immune system best, and so there is more and more evidence growing in this area.

A clinical trial3 conducted in 2018 found that the probiotic strains Lactobacillus paracasei CASEI 431® and Lactobacillus fermentum PCC® are ‘effective for fighting the common cold and influenza-like respiratory infections’.

The study also revealed that the number of participants experiencing symptoms of upper respiratory tract infection (URTI) without a fever was reduced in those who took probiotics. Additionally, those in the probiotic group required less medications for their URTI symptoms, compared to those not taking probiotics.

Therefore, when looking to support your immune health, you might consider probiotic supplements containing Lactobacillus paracasei CASEI 431®.

Health Professionals can read more about Lactobacillus paracasei CASEI 431® over at the Probiotics Database.

Can probiotics help with children’s immunity?

In addition to research carried out on adult populations, researchers have also looked at the impact of probiotics on the immune systems of children.

A study from 20144 observed the effects of probiotic species Lactobacillus acidophilus, Bifidobacterium bifidum and Bifidobacterium lactis, coupled with 50 mg vitamin C or placebo on 57 children aged 3 - 5 years old. The aim of the study was to investigate the effect of the probiotic formula and vitamin C against upper respiratory tract infections, generally known as common colds, in children attending preschools.

The results revealed that the children who received the probiotic and vitamin C combination were 33% less likely to contract URTIs and, consequently, were less likely to miss school days by 30%, when compared to the placebo group. As well as this, those taking probiotics and vitamin C were less reliant on medicines such as antibiotics, painkillers, cough medicine or nasal sprays.

A further study5 revealed that a different probiotic supplement, containing the strains Lactobacillus acidophilus Rosell-52, Bifidobacterium infantis Rosell-33, Bifidobacterium bifidum Rosell-71 and prebiotics was able to reduce the risk of occurrence of common infectious diseases in children.

Those taking the probiotic formula were 25% less likely to contract common winter diseases and their risk of absence from school due to illness was also reduced.

Both trials showed great results for the effects of specific probiotic strains on the immune systems of children.

woman with a cold
Can good bacteria help with cold and flu symptoms? The research says yes.

Too late, I’ve already got a cold or the flu - can probiotics still help my immune system?

With luck, you’ve stumbled across this blog before catching a nasty cold or virus bug. However, if you’re already experiencing symptoms, and are firmly in the coughing and sneezing camp, don’t lose hope. It’s never too late to start building up your good bacteria.

In fact, research done in the U.S6 shows that taking probiotics may shorten the duration of colds.

The Chr. Hansen-sponsored study observed a group of 200 student participants, with half receiving the probiotic strains L. rhamnosus LGG and B. lactis BB-12® probiotic formula. The researchers observed that those taking the probiotics experienced colds that lasted an average of 4 days, as opposed to 6 in the placebo group. The probiotic group also experienced a 34% reduction in cold symptom severity.

Birgit Michelsen, Chr. Hansen’s director of scientific affairs in health and nutrition commented on the significance of the study, “There have been other studies that have shown similar effects but this shows a significant result in a key population typically under extreme stress and prone to colds and flus as a result.”

So, whether you’re fit and healthy (and aiming to stay that way), or are already experiencing symptoms and need some TLC, probiotics can be a great addition to your daily health regime.


  • There are trillions of microbes living in the human gut, known as the ‘microbiome’
  • The health of the microbiome is vital to the health of the immune system
  • Our probiotic colonies can ‘talk to’ the cells of our immune system
  • These friendly bacteria help to prevent pathogen overgrowth and create a protective barrier in the gut to reduce infections
  • Using well-researched strains of probiotic bacteria can support a healthy immune response
  • Lactobacillus paracasei CASEI 431® is one strain of probiotic that has been shown to reduce the likelihood of catching common colds and flu, and also to reduce their duration and severity

Got the gut health bug? Read more:

Probiotics and Antibiotics: Can I Take Both?

Probiotics for Men

Meet the Gut Brain Axis

Gut Health: All You Need To Know

Health Professionals may also like to head over to ‘Probiotics Professionals’ and read:

Probiotics for Immunity


  1. Montalban-Arques A et al (2015) Selective Manipulation of the Gut Microbiota Improves Immune Status in Vertebrates, Frontiers in Immunology. 6:512
  2. Mintel, (2019). ‘D outshines C to become the UK’s favourite single vitamin supplement’. [Online] Available at: [Accessed 14 Oct. 2019]
  3. Zhang H et al., (2018) “Prospective study of probiotic supplementation results in immune stimulation and improvement of upper respiratory infection rate,” Synthetic and Systems Biology. 3(2): 113-120
  4. Garaiova, I. et al (2014) Probiotics and vitamin C for the prevention of respiratory tract infections in children attending preschool: a randomised controlled pilot study. European Journal of Clinical Nutrition. 69(3):373-9. doi: 10.1038/ejcn.2014.174
  5. Cazzola M. et al., (2010) ‘Efficacy of a synbiotic supplementation in the prevention of common diseases in children: a randomized, double-blind, placebo-controlled pilot study’ Therapeutic Advances in Respiratory Disease, 0(0):1-8.
  6. Smith J. et al, (2013). Effect of Lactobacillus rhamnosus LGG® and Bifidobacterium animalis ssp. lactis BB-12® on health-related quality of life in college students affected by upper respiratory infections. British Journal of Nutrition. 109(11):1999-2007. doi: 10.1017/S0007114512004138. Epub 2012 Oct 1.