Only some probiotics are able to survive the harsh environment of the human digestive tract, say researchers.
For instance, the lactobacilli strains showed the highest survival rate in the 'model digestive system,' which mimicks the human digestive system, developed by a team from the Norwegian University of Life Sciences, as compared to other strains of probiotic bugs.
They also found that some of these strains survive better when consumed as fermented milks, the Journal of Dairy Science reports.
The initial testing in acid and bile salts found that Lactobacillus strains had a significantly higher acid tolerance than the lactococci strains and E. hirae, according to a Norwegian statement.
"We wanted to evaluate whether these strains . . . have the potential as probiotics for human consumption," explains lead investigator Siv Skeie, professor of chemistry, biotechnology, and food Sciences at Norway University.
Researchers tested five Lactococcus bacteria strains, found in ropy milks, traditional Nordic fermented milk products said to have beneficial effects on consumer health, as well as three Lactobacillus strains, and one strain of Enterococcus hirae.