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.
