We rarely think about our gut, let alone its contents. The microbial community (or microbiome) that resides within it outnumber the cells within the body by 10 to 1! What do we know about these mysterious bacteria that live within us, how could they benefit our health and can we influence them? Registered nutritionist Claire Baseley investigates.
The role of gut bacteria in digestion
The food we eat is digested at several points within the body and the nutrients that are released are mainly absorbed in the small intestine. However, it’s when what is left over from the digestive process reaches the large intestine or colon that things get really interesting. These leftover nutrients include forms of starch that are tough to digest and various types of fibre, including what’s known as ‘prebiotics’. These can be consumed by certain species of gut bacteria but crucially not others and these bacteria consequently release by-products known as short chain fatty acids (SCFAs) that are absorbed and utilised by the body and can have potential health benefits.
How do gut bacteria influence our health?
There are over 500 species of bacteria within our gut and the type and balance of species varies widely between individuals. Disruption to the balance of the microbiome has been linked to obesity, diabetes, osteoporosis and even colon cancer. Studies are beginning to show that changes to the microbiome that boost the number of beneficial bacterial species and reduce the number of potentially pathogenic species can have health benefits, potentially due to the production of SCFAs. These changes seem to influence the immune system, the body’s sensitivity to insulin, our appetite and may even protect against certain types of cancer. Early research also indicates that the microbiome may even positively influence our mood and response to stress!
Practical advice for the public
Our diet can influence our balance of gut bacteria and studies suggest that this can happen relatively quickly after changing the foods we eat (for the better or worse). Consuming a source of prebiotics, which are the preferred food of the beneficial gut bacteria can help to boost their numbers. It’s best to eat a variety of sources of these prebiotics, which can be found in foods like onion, leek, garlic, chicory and artichoke, as well as fortified foods (look out for inulin, fructo-oligosaccharides and galacto-oligosaccharides).
Prebiotics can only feed bacterial species that already exist in the gut, so they can only affect the numbers and not the type of species present. Is there a case for supplementing with probiotics i.e. the bacteria themselves? Maybe but at present, we need far more research to identify the beneficial bacterial species and their mode of action. A better approach may be to eat a variety of fermented foods like yoghurt, sour cream, sauerkraut, kefir and kimchi alongside a balanced diet that contains plenty of vegetables, fruits and pulses with moderate amounts of meat and fish.
In the future, research may enable us to personalise nutrition to an individual’s needs based upon their specific gut bacteria.