Probiotics and the Immune system
Updated: Jan 14
Our immune system is getting a lot of attention at the moment; how we can ‘boost’ it through nutrition is everywhere.
I’m very sorry to disappoint you, but there is no immune boosting miracle nutrient that can magically make our immune system function perfectly and stop us from catching a virus. Or any disease or illness for that matter. However, all is not lost. There are other aspects of our overall heath that can be influenced by our diet, which may improve our immune function.
Interest in our gut health has sky rocketed in the last few years, with research being undertaken on how our gut microbiome interacts with the rest of our body. There has been emerging and convincing evidence that our microbiome is extremely important for optimal health; not only to decrease the risk of developing or acquiring diseases, but it may also play a vital role in ensuring good mental health.
What is our microbiome?
Our large intestine is colonised by millions of resident bacteria. These bacteria have been found to have many beneficial roles in our body, including helping our immune system fight off foreign microbes. The more gut bacteria we have and the more diverse the strains of bacteria, the more health benefits we will get.
So how can we increase the number and diversity of these important microbes?
This can be achieved through our diet. For example, we can consume foods that are known to be prebiotics (compounds that will feed the bacteria so they can grow and increase in number). There are also probiotics. Many of you may have heard of these as supplements endorsed by the health and wellness industry on social media to be the next best health supplement for 'eternal life' and wellbeing. Probiotic supplements are strains of bacteria that you can take which will colonise our large intestine and directly increase the number of bacteria.
But are these supplements really a magic cure, and will taking them boost our immune system?
A recent systematic review and meta-analysis (a study reviewing all the evidence that has been published), evaluated the scientific evidence of the effects of probiotic supplementation on the function of specific immune cells in the elderly (1).
What were these researchers measuring?
The researchers wanted to determine whether probiotic supplements influence the function of specific immune cells; white blood cells known as neutrophils and also natural killer cells. These cells are part of our innate immune response. This immune response acts as a surveillance system, the cells can recognise foreign microorganisms and upon recognition of a virus for example they kill it and signal to other immune cells, activating the whole of the immune system. Measuring the activity of these cells after taking probiotic supplements may be able to give us an indication of how well our immune system is working.
What did they find?
The researchers compared the results of 17 controlled trials, each of which looked at the effect of probiotic supplementation in healthy elderly people for 3 to 12 weeks. They found that probiotic supplementation increased the activity of both the white blood cells and the natural killer cells.
So, should we be all taking probiotics?
I don’t want to be a kill joy but don’t rush to order huge quantities of these supplements thinking that they are the magic pill. Despite these interesting findings and the positive effect that probiotics appears to have on our immune system, more research is still needed. So please refrain from panic buying probiotics!
What are the issues with this research and why is more research needed?
To start with, the trials were only undertaken over relatively short periods of time, so we have no idea what the long terms effects will be if people are taking these supplements for more than 12 weeks.
Another question which has not been answered is which probiotic strain is best. There are many different types of bacteria strains which are used in supplements, each of which carry out varying roles with varying health benefits. However, the individual strains of probiotics were not looked at in this study, so we don’t actually know which one is best for supporting out immune function.
These studies were also only analysing the use of probiotics in healthy elderly people. Will probiotics have the same effects in elderly people with pre-existing health issues or who are already suffering from an illness? I know for a fact that my grandparents can’t be classed as ‘healthy’, so what effect will these supplements have on their immune system? And will these beneficial effects also be seen in younger people?
And lastly, despite these positive findings, that probiotic supplements increase the activity of certain immune cells, what does this mean in terms of how our immune system responds to a foreign microorganism? Will the probiotics actually enhance our immune response and make it better at fighting off the virus or bacterial infection? The clinical outcomes of probiotic use were not measured, so we have no idea what the overall effect of these supplements have on our immunity.
It's not all doom and gloom…I promise
For now, the best thing we can do for our gut microbiome and our immune system is eat a well-balanced diet, high in fruit and vegetables and dietary fibre. Fibre is the nutrient that bacteria in our guts LOVE to eat, it is a prebiotic, and none of us are eating enough of it. Fermented foods that contain live bacteria are also readily available to buy such as kefir and kombucha.
Below I have listed foods which are high in fibre that can promote gut health, in addition to foods that already contain bacteria; your pre- and probiotics! Try to include as many of these in your diet as you can, varying them week by week.
These are generally fermented foods and include:
Kefir - fermented milk
Kombucha - fermented tea
Miller LE, Lehtoranta L, Lehtinen MJ. Short-term probiotic supplementation enhances cellular immune function in healthy elderly: systematic review and meta-analysis of controlled studies. Nutrition Research. 2019;64:1-8.