Health effects of probiotics

banner_probioticsPhoto courtesy of CDC/ Melissa Dankel

Project Description
Probiotics are live microorganisms which, when administered in adequate amounts, confer a health benefit to the host. An example of a probiotic is Lactobacillus casei Shirota (marketed as Yakult). Several positive health effects can be attributed to probiotics, including the prevention and reduction of diarrhoea and constipation. In addition to the influences in the gastrointestinal tract, probiotics also have a widespread systemic effect. One can think of prevention of allergies (atopic dermatitis, asthma), but also strengthening the immune system and boosting vaccine immunization. Furthermore, there are indications that probiotics could even have an effect in autism and anxiety (gut-brain-axis).

Despite the wide range of potential health benefits that probiotics have, currently little to no probiotics are used for medical conditions.
Lack of regulation resulted in a flooding of the market by poor characterized and ineffective probiotics. In response, the EFSA/FDA rejected health claims for all probiotic strains, even those with a reasonable evidence-base. Several factors play an important role in this issue. There is still great controversy regarding the efficacy of probiotics. Due to large variety in strains, administration regimes and a lack of biomarkers, it remains unclear if probiotics are even effective. In addition it is not clear how probiotics should be evaluated with respect to health claims (as a drug through the pharma-principle or as a dietary supplement/medical food). Furthermore, with the recent failed PROPATRIA study in Utrecht in mind, it became unclear whether probiotics are even safe, especially in the highly vulnerable population. Investigators became hesitant in exploring the potential of probiotics in this population, who could benefit the most from probiotic administration. Also, why is there so little innovative with respect to new probiotic strains? And where should new innovation focus on? These are some issues we address in my project. Using quantitative (clinical trials) and qualitative studies, barrier analyses and safety studies we are trying to uncover the full potential of probiotics in human health.

External Website

Maurits van den Nieuwboer, MSc
Prof. dr. Eric Claassen


  • Van den Nieuwboer, M., Claassen, E., Morelli, L., Guarner, F., & Brummer, R. J. (2014). Probiotic and synbiotic safety in infants under two years of age. Beneficial Microbes, 5(1), 45-60.
  • Van den Nieuwboer, M., Brummer, R. J., Guarner, F., Morelli, L., Cabana, M., & Claasen, E. (2015). The administration of probiotics and synbiotics in immune compromised adults: is it safe? Beneficial Microbes, 6(1), 3-17.
  • Van den Nieuwboer, M., Brummer, R. J., Guarner, F., Morelli, L., Cabana, M., & Claasen, E. (2015). Safety of probiotics and synbiotics in children under 18 years of age. Beneficial Microbes, In press.
  • van den Nieuwboer, M., Klomp-Hogeterp, A., Verdoorn, S., Metsemakers-Brameijer, L., Vriend, T., Claassen, E. & Larsen, O.F.A. (2015). Improving the bowel habits of elderly residents in a nursing home using probiotic fermented milk. Beneficial Microbes, in press.
  • Van den Nieuwboer, M., van Hemert, S., Claassen, E. and de Vos, W. (2015). Lactobacillus plantarum WCFS1: 10 years after the genome. Microbial Biotechnology, in press.