Probiotics or prebiotics

The microbiome (also known as gut flora) of the human gut has around 1014 microorganisms. These bacterium and yeasts residing within your gut are known as probiotics, while prebiotics is known to be their ‘food’. All prebiotics are fibres (and not to confuse things but not all fibres are prebiotics); these prebiotic fibres such as galactooligosaccharides, lactulose and inulin can be found in such foods as chicory root, garlic, onions, leeks and oats to name a few. Probiotics such as Lactobacillus, Bifidobacterium and Saccharomyces boulardii can be found in certain fermentable foods such as yoghurts.

What does the evidence say?


A study of 400 patients published in May of this year showed evidence to say probiotics can have significant improvements in symptoms relating to those with diarrhoea predominant irritable bowel syndrome (IBS-D). Another study stated that probiotics in the treatment of IBS were effective when they found it had beneficial effects on abdominal pain, bloating, and flatulence, although further research needs to be carried out to determine which species and strains are the most effective. In a study of two groups, one given the strain Bifidobacterium longum NCC3001, the other a placebo, it was found that the probiotic reduced depression and increased quality of life in those with IBS.

Effects of probiotics are not always beneficial. In a small number of cases, probiotics can induce infections with the development of sepsis in patients whom are already diseased. However, many studies show that some probiotics enhance the immune response against pathogens and therefore those who are critically ill or who have an increased risk of becoming critically ill will benefit the most.


One animal study indicated when an inulin-type fructan was ingested, gut bacteria increased significantly and a decrease of lipopolysaccharide, fat mass and an increase of glucose tolerance was seen. The use of this prebiotic has also seen positive results for weight loss in clinical trials.

A decrease in Clostridium difficile–associated diarrhoea has been observed during a study of one group receiving oligofructose compared to the second group receiving a placebo during antibiotic treatment. Another study with the focus on depression saw reductions in the waking-cortisol response; this is a biomarker for depression when exaggerated.

Probiotics on the shelf

Manufacturers are challenged in ensuring their probiotics contain live, viable microorganisms. Dairy probiotic products have considerably reduced shelf-life compare to freeze-dried products such as powders and pills. But even when freeze-dried, oxygen, moisture and storage can affect the stability. Note that it is unavoidable for dead or injured microbes to be present in commercial products due to the very specific conditions needed as a constant which it seems cannot be maintained.

It is important to know that probiotics are regulated like foods, not like medications, both in the UK and USA. This means manufacturers do not need to show their products work or are even safe. When 19 probiotic products were tested, five of them had lower counts of bacteria than what they listed, and in some cases had other bacteria present in addition to those on the label.

Final thought

Our gut microbiota plays an important role in our overall health. Both probiotics and prebiotics may be used as preventative and therapeutic agents within medical disorders with possible beneficial results. However, it does depend on the cause of disease, strain/type of these products and the research that was carried out to determine their effectiveness.


Bamberger, C., Rossmeier, A., Lechner, K., Wu, L., Waldmann, E., Fischer, S., Stark, R., Altenhofer, J., Henze, K. and Parhofer, K. (2018). A Walnut-Enriched Diet Affects Gut Microbiome in Healthy Caucasian Subjects: A Randomized, Controlled Trial. Nutrients. [Online] 10 (2), 244. Available from:

Ford, A., Quigley, E., Lacy, B., Lembo, A., Saito, Y., Schiller, L., Soffer, E., Spiegel B., Moayyedi, P. (2014). Efficacy of prebiotics, probiotics, and synbiotics in irritable bowel syndrome and chronic idiopathic constipation: systematic review and meta-analysis. The American Journal of Gastroenterol. [Online] 109 (10), 1547-61. Available from:  

Ishaque, S., Khosruzzaman, S., Ahmed, D. and Sah, M. (2018). A randomized placebo-controlled clinical trial of a multi-strain probiotic formulation (Bio-Kult®) in the management of diarrhoea-predominant irritable bowel syndrome. BMC Gastroenterology. [Online] 18 (1). Available from:

Patel, R. and DuPont, H. (2015). New Approaches for Bacteriotherapy: Prebiotics, New-Generation Probiotics, and Synbiotics. Clinical Infectious Diseases. [Online] 60 (2), 108-S121. Available from:

Pinto-Sanchez, M., Hall, G., Ghajar, K., Nardelli, A., Bolino, C., Lau, J., Martin, F., Cominetti, O., Welsh, C., Rieder, A., Traynor, J., Gregory, C., De Palma, G., Pigrau, M., Ford, A., Macri, J., Berger, B., Bergonzelli, G., Surette, M., Collins, S., Moayyedi, P. and Bercik, P. (2017). Probiotic Bifidobacterium longum NCC3001 Reduces Depression Scores and Alters Brain Activity: A Pilot Study in Patients With Irritable Bowel Syndrome. Gastroenterology. [Online] 153 (2), 448-459.e8. Available from:

Sanders, M., Akkermans, L., Haller, D., Hammerman, C., Heimbach, J., Hörmannsperger, G. and Huys, G. (2010). Safety assessment of probiotics for human use. Gut Microbes. [Online] 1 (3), 164-185. Available from:

Schmidt, K., Cowen, P., Harmer, C., Tzortzis, G., Errington, S. and Burnet, P. (2014). Prebiotic intake reduces the waking cortisol response and alters emotional bias in healthy volunteers. Psychopharmacology. [Online] 232 (10), 1793-1801. Available from:

Nutritionist Resource is not responsible for the articles published by members. The views expressed are those of the member who wrote the article.

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