Probiotics: does it bring anything?

The dysbiosis concept

As I wrote in my last post, there are several diseases which are supposed to be linked with an unhealthy gut microbiome. A recently common concept is the connection between dysbiosis – an unfavorable change in the composition of the microbial community – and health. It is likely that dysbiosis can provoke inflammations, obesity and diabetes[1]. A study by Ley et al. claims a connection between obesity and the ratio of Bacteroidetes in the gut microbiome[2].  

The question, if probiotics really are able to change the composition of a dysbiotic gut microbiome is discussed in the moment. Kristensen et al. investigated seven different studies on effects of probiotics on fecal microbiota[3]. In none of these the probiotics had a significant influence on the composition of the microbiota. Additional research is needed. Interesting would also be to research on the question, if probiotics can make the existing gut microbiome more resistant against disturbances.

Effects of probiotic organisms on gut microbiota and human health

The most frequently used microorganisms in commercial probiotic products are members of the genera Lactobacillus and Bifidobacterium but also Escherichia coli, enterococcus, certain Bacillus species, Saccharomyces boulardii and Saccharomyces cerviciae are employed[4]. There are several in clinical studies reported effects of probiotics with Lactobacillus or Bifidobacterium organisms such as lowering faecal enzyme activity, immune enhancing, tempering diverse sorts of diarrhea or balancing intestinal microflora [5]. Another interesting study showed that probiotics with Bifidobacteria can help to prevent inflammatory disorders by attenuating the gut permeability for endotoxemia. Endotoxemia are produced in order to a high-fat diet and can have inflammatory effects[6].

Probiotic cultures are claimed to have numerous of other effects on the human gut microbiome. For example they are able to change the metabolic properties of the indigenous microbes by competition for food[7]. Another possible effect is the changing of the microenvironment caused by the metabolic pathway outcomes of the probiotic organisms (e.g. cecal short-chain fatty acids, choline, ethanol)[8]. Probiotic organisms may are able to competitive exclude other (also pathogenic) microorganisms, they can act as a barrier on the gut epithelium or produce growth substrates (see Figure 1)[9].

Figure 1: Possible effects of probiotic organisms on human gastrointestinal microbiota

Should commercial be allowed to claim any positive effect of probiotic products?

The mechanisms of probiotic effects are still nowadays not completely understood. There are a lot more in vitro than in vivo studies and just few in human. So, the validity of most of the studies is not necessary given for the human organism.

As the knowledge on how probiotics effect our health is still really small I think commercial companies shouldn’t be allowed to claim any positive effect. I believe there is a great potential in biotics, but more in medications which are especially made for certain diseases. Probiotics in food are in my opinion to general. I rather believe in a necessity of studies, which investigate how our food behavior can affect our gut microbiome. Because the “probiotics” in natural, untreated food are free.

References

1          P. Hemarajata, J. Versalovic Effects of probiotics on gut microbiota: mechanisms of intestinal      immunomodulation and neuromodulation. (2013) Ther. Adv. Gastroenterol. 6, 39–51.

2          R. E. Ley, P. J. Turnbaugh, S. Klein, J. I. Gordon Microbial ecology: Human gut microbes associated with obesity. (2006) Nature. 444, 1022–1023. 

3          N. B. Kristensen, T. Bryrup, K. H. Allin, T. Nielsen, T. H. Hansen, O. Pedersen Alterations in fecal microbiota composition by probiotic supplementation in healthy adults: a systematic review of randomized controlled trials. (2016) Genome Med. 8, 52. 

4          Y. Ringel, E. M. Quigley, H. C. Lin Using Probiotics in Gastrointestinal Disorders. (2012) Am J Gastroenterol Suppl. 1, 34–40. 

5          W. H. Holzapfel, P. Haberer, J. Snel, U. Schillinger, J. H. . Huis in’t Veld Overview of gut flora and probiotics. (1998) Int. J. Food Microbiol. 41, 85–101. 

6          P. D. Cani, N. M. Delzenne Interplay between obesity and associated metabolic disorders: new insights into the gut microbiota. (2009) GastrointestinalEndocrine Metab. Dis. 9, 737–743. 

7          J. L. Sonnenburg, C. T. L. Chen, J. I. Gordon Genomic and Metabolic Studies of the Impact of Probiotics on a Model Gut Symbiont and Host. (2006) PLOS Biol. 4, e413. 

8          F. J. Martin, Y. Wang, N. Sprenger, I. K. S. Yap, T. Lundstedt, P. Lek, et al. Probiotic modulation of symbiotic gut microbial–host metabolic interactions in a humanized microbiome mouse model. (2008) Mol. Syst. Biol. 4,. 

9          P. W. O’Toole, J. C. Cooney Probiotic Bacteria Influence the Composition and Function of the Intestinal Microbiota. (2008) Interdiscip. Perspect. Infect. Dis. 2008, 1–9.