If probiotics have success for boosting human health (that is in doubt, despite the number of papers capitalizing on the craze) it may depend partly upon the food or other material carrying the probiotics, according to a paper in Applied and Environmental Microbiology.
In the paper, the researchers investigated the probiotic strain Lactobacillus casei BL23 in a mouse model (so calibrate its relevance accordingly) of colitis; inflammation of the colon. The mice that ingested the probiotic in milk had reduced symptoms compared to those that were fed milk without the probiotic, and the ones that received the probiotic within a nonfood supplement.
The investigators also took a census of the microbiota before and after ingestion of L. casei. "This did not significantly alter the populations or diversity of the resident gut bacteria, suggesting that the benefits of the probiotic involve a direct effect of L. casei, or of a metabolic product of these bacteria upon the intestinal epithelium, rather than a global alteration of the indigenous intestinal microbiota," said corresponding author Maria Marco, Ph.D., an associate professor in the Department of Food Science and Technology, at the University of California at Davis. "Strains of L. casei are commonly added to dairy products as probiotics and, while strain BL23 is not commercially available, it is genetically similar to commercial strains and has also been studied for its capacity to prevent or reduce intestinal inflammation."
Dairy products are the food fad of choice for probiotics.
"Remarkably, the question of whether it makes any difference to consume probiotics in dairy products rather than other foods or nutritional supplements has not been systematically or mechanistically investigated in clinical or preclinical studies. Because we know that bacteria can adapt to their surroundings, we thought the conditions that probiotics are exposed to prior to ingestion might influence their capacity to maintain or improve human health."