Early immune education
Your immune system starts to develop before you are born and the majority of it is built during childhood, the majority being developed from conception to 5 years of age. The majority of your immune systems is located in your gut. The microbes in your gut (your ‘gut microbiota’) educate your immune cells early on. Those educated immune cells don’t just stay in your gut either, they travel all over your body and set the tone for immunity later in life. Major changes to your gut microbiota can send your immune system a bit cray cray causing inflammation and long term consequences lasting until adulthood, but luckily you can recover and build immunity.
You get the basics of your gut microbiota from your mum while you are in the womb and she got hers from her mum and so on (1, 2). The next place you acquire more microbes to add to your gut microbiota comes from birth. Babies born vaginally acquire microbes inhabiting mum’s vagina, bowel, and skin and those born surgically acquire microbes from mum’s skin and birth environment (3). The difference between the gut microbiota of babies born vaginally and those born surgically can persist until children are at least 7 and those born surgically are more likely to experience certain immune disorders (4, 5). But it isn’t just mode of delivery that determines the make-up of your gut microbiota and immune system, environmental factors play a large part too.
Environmental exposure to microbes has a big impact on the make-up of the gut microbiota. Breastmilk, a kind of nutritious bacterial and soup, is another way mum can pass on bacteria to baby and help shape the blueprint of the gut microbiota for years to come (6). Breastmilk is also a prebiotic, meaning it contains food for your gut microbiota to thrive and supports the development of the immune system (7). The bacteria passed on through breast milk is associated with a reduced risk of developing asthma.
In addition to the mode of delivery, whether or not you are breastfed, the food you are exposed to, in particular, the diversity in your diet, has a huge impact on your gut microbiota and your immune system throughout childhood and into adulthood. How your own microbial fingerprint develops in early childhood can either reduce or increase your risk of developing allergies, autoimmune conditions, and inflammatory disease later on in life (9, 10, 11, 12).
A healthy microbiota
It’s easy to romanticise the idea of a healthy microbiota. But what really constitutes healthy? We just don’t have the research to support the idea that there is specific criteria for a microbiome that’s healthy versus one that isn’t. Scientifically speaking the hallmark of a healthy microbiota is still ill-defined but study after study shows that diversity is good; an inherent rich and stable ecosystem is the root of resistance and resilience when it comes to our health. So if you were a c-section baby who was formula fed you may be feeling like your gut microbiota, is like the world’s coral reef – a fraction of what it should be. Is there anything else you can do to restore these crucial microbial inputs your immunity has evolved to require, how can you build immunity?
Diversity and fibre
Your gut microbiota need fibre and a diverse range of foods to thrive so aim to get 30 different plant-based foods in your diet a week.
Pets carry their own microbiota and research shows they may even support your microbial diversity and build immunity (14). Children growing up with pets have a lower risk of developing allergies. So what are you waiting for? Get your own or borrow a furry friend to share some of their microbes.
Antibiotics disrupt your gut microbiota and not for the better. Try to avoid taking unnecessary antibiotics if you want to build immunity but always be advised by your doctor.
A major part of the trick on how to build immunity is with dirt. Dirt is good. Disconnection from nature is not. Not only are cities, modern sterilised life and dearth of greenery, all affecting our mental health but our microbiota too and consequently our immunity. Ditch your hand sanitiser and just wash your hands instead, get outside, gardening, picking vegetables with a bit of dirt on, or just have a lay down on the grass in a park
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2. Walker, R. W., Clemente, J. C., Peter, I., & Loos, R. J. F. (2017). The prenatal gut microbiome: are we colonized with bacteria in utero? Pediatric Obesity, 12 Suppl 1(Suppl 1), 3–17. https://doi.org/10.1111/ijpo.12217
3. Dominguez-Bello, M. G., Costello, E. K., Contreras, M., Magris, M., Hidalgo, G., Fierer, N., & Knight, R. (2010). Delivery mode shapes the acquisition and structure of the initial microbiota across multiple body habitats in newborns. Proceedings of the National Academy of Sciences of the United States of America, 107(26), 11971–11975. https://doi.org/10.1073/pnas.1002601107
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14. Hesselmar, B., Hicke-Roberts, A., Lundell, A.-C., Adlerberth, I., Rudin, A., Saalman, R., … Wold, A. E. (2018). Pet-keeping in early life reduces the risk of allergy in a dose-dependent fashion. PLOS ONE, 13(12), e0208472. https://doi.org/10.1371/journal.pone.0208472