Overall, the human gut microbiome consists of  1014  micro-organisms, which include a variety of bacteria, viruses, fungi and protozoa (1). Although the number of micro-organisms in the body is almost unthinkable, a large percentage of them are made up of bacteria, more specifically: Firmicutes and Bacteroidetes. In research of late, there is a growing interest in gut microbiota adaptations, which can occur over 24 hours through a change in diet. 

What are pro- and prebiotic bacteria?

Probiotic bacteria are living organisms in the gut that can improve health when present in an adequate amount. Probiotics can reduce inflammation in the body, lower the overall gut pH (neutralising the gut from an alkalotic state) and improve the immune response. There are many forms of probiotic and every strain possess different health benefits. Strong evidence has been concluded to suggest that foods or medication containing probiotics are able to help cure diarrhoea (2). Probiotics are often found in fermented foods, such as yoghurts, sauerkraut and other dairy products. 

Prebiotics, on the other hand, are a unique source of fibre that aid probiotics in their fermentation and aiding the digestive system with increasing bacteria. Prebiotic fibre can pass through the small intestine without being digested, allowing for improved digestion further down the digestive tract. Foods that include probiotic are bananas, onions, beans and apple skin. An analogy often used to help gain a further understanding of pro- and prebiotics is shown by Dr Frank W. Jackson. The seeds can be planted (probiotics), but they will need water and fertiliser (prebiotic fibre) to grow optimally. 

Why is maintaining gut health important?

A major responsibility of gut health is to regulate the immune system. Probiotics have the ability to renew, restore and grow affected tissues that line the digestive system. Valuable live micro-organisms aid the regeneration of microflora, improving overall health (3). 

How you can improve gut health?

Improving gut health can be achieved with several easily implementable changes in everyday life. Both omnivorous and vegetarian lifestyle choices can achieve a healthy gut. Improvements in gut health have been seen with a substitution of saturated fats for unsaturated fats, ultimately lowering total cholesterol (4). Highly processed foods and the over-prescription of antibiotics can be a hindering factor to gut health. 

The fermentation of foods is an ancient practice, which has been proven to improve the nutritional qualities in many ways. The proposed benefits of fermented foods are that they improve cardiovascular health and decrease the risk of type two diabetes (5).  Fermented foods will often consist of 5-40% of an individual's diet, dependent on the population.

Foods that contain natural sugars, such as many fruits and vegetables will not only improve overall gut bacteria, but they will offer irreplaceable vitamins and minerals. Contrary to this, artificial sugars have been proven to reduce helpful bacteria in the body, such as Bifidobacteria and Lactobacilli, whilst increasing the appearance of Bacteroides (the ‘bad’ bacteria). Furthermore, it’s recommended that each adult should consume around 30g of dietary fibre per day, whereas the currently estimated intake is approximately 17 and 20g on average for women and men, respectively. 

Last but certainly not least, making sure that you consume a variety of foods, as each different type of food will possess a diverse set of bacteria to the next. 


  1. Gill, S.R., Pop, M., DeBoy, R.T., Eckburg, P.B., Turnbaugh, P.J., Samuel, B.S., Gordon, J.I., Relman, D.A., Fraser-Liggett, C.M. and Nelson, K.E., 2006. Metagenomic analysis of the human distal gut microbiome. science, 312(5778), pp.1355-1359.
  2. Sazawal, S., Hiremath, G., Dhingra, U., Malik, P., Deb, S. and Black, R.E., 2006. Efficacy of probiotics in prevention of acute diarrhoea: a meta-analysis of masked, randomised, placebo-controlled trials. The Lancet infectious diseases, 6(6), pp.374-382.
  3. 3.  Reid, G., Sanders, M.E., Gaskins, H.R., Gibson, G.R., Mercenier, A., Rastall, R., Roberfroid, M., Rowland, I., Cherbut, C. and Klaenhammer, T.R., 2003. New scientific paradigms for probiotics and prebiotics. Journal of clinical gastroenterology, 37(2), pp.105-118.
  4. Wolters, M., Ahrens, J., Perez, M.R., Watkins, C., Sanz, Y., Benítez-Páez, A., Stanton, C. and Günther, K., 2018. Dietary fat, the gut microbiota, and metabolic health–A systematic review conducted within the MyNewGut project. Clinical Nutrition.
  5. Rezac, S., Kok, C.R., Heermann, M. and Hutkins, R., 2018. Fermented foods as a dietary source of live organisms. Frontiers in microbiology, 9.


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