There are at least nine case reports of severe, invasive (internal) fungal infections developing in people treated with the yeast organism Saccharomyces boulardii. All of these people were debilitated or had impaired immune function prior to receiving Saccharomyces boulardii. No such adverse reactions have been reported with other probiotic supplements or in people with normal immune systems.
In one study, treatment of infants with a product containing probiotics (Lactobacillus rhamnosus
GG, L. rhamnosus
, Bifidobacterium breve
Bb99, and Propionibacterium freudenreichii
JS) plus a prebiotic (a galacto-oligosaccharide) resulted in a decrease in hemoglobin levels at six months of age. The authors of this report suggested that this effect may have been due to intestinal inflammation. This adverse effect has not been reported in older people, and it is not known whether other probiotics would have the same effect in infants.