Probiotics containing a single bacterial strain are more effective at increasing cytokine production than combination products according to Finnish researchers.
Researchers from Finland's National Public Health Institute, the University of Helsinki and Finnish dairy giant Valio's Research Centre tested 11 strains of bacteria from 6 genera. These included Lactobacillus and Bifidobacterium species which are currently the most common in probiotic products.
Each of the "potentially probiotic' strains of bacteria were used to stimulate a type of immune cell called human peripheral blood mononuclear cells (PBMC). Changes in the types and amounts of cytokines produced by the cells were then closely monitored.
Cytokines are chemical messengers that the immune system uses to coordinate the various immune cells to maintain defences against pathogens and keep things in balance to avoid allergies and autoimmune reactions.
The researchers found that all 11 strains tested induced a cytokine reaction when used alone but in combination they were found to have little or no effect on cytokine production. The most potent bacterial strains were found to be types of Streptococcus (especially S. thermophilus) and Leuconostoc. S. thermophilus is often included in combination probiotic products but rarely by itself.
These findings could be very important as at present a large proportion of probiotics on the market are in the form of combination products which may contain as many as 10 different bacteria.
The researchers said their results provide evidence that different bacterial strains compete with each other and can cancel out the effects a single strain might have on immune responses.
They also said the results demonstrate that probiotic bacteria have the potential to direct immune responses in a "bacterial genera-specific manner" and explained that this potentially meant that probiotic products could be produced for the prevention and treatment of specific conditions, once further research specific to these conditions has been conducted.
The research represents a new area of investigation as the effects of combination probiotic products on cytokine production in the body is not well understood. The results do not mean however that combination products are not useful however as many clinical trials have used combination products for a range of conditions from digestive disorders to asthma and found them in many cases to be effective.