Caveat emptor. "Probiotics" might not be what they seem.

OBJECTIVE To assess whether commercially prepared probiotic products contain viable organisms, as claimed by their manufacturers, particularly whether products labeled as containing Lactobacillus did so. To identify and quantify as many species as feasible and to compare them with the contents listed on labels.

DESIGN Randomized, double-blind trial.

SETTING Community hospital in Chilliwack, BC.

MAIN OUTCOME MEASURES Trial of 10 randomly chosen brands of probiotic preparations bought over-the-counter in British Columbia's lower mainland. Only products claiming to contain lactobacillus were included in this study. Viable organisms in each probiotic brand and quantities of Lactobacillus in each product.

RESULTS None of the 10 products tested matched their labeled microbiologic specifications. Two brands grew nothing aerobically or anaerobically. No Lactobacillus grew in five brands, although their labels stated that this was the main species. Eight brands contained viable cells, but only 10% of the number stated by their manufacturers.

CONCLUSION Most product labels did not adequately identify or quantify microbes. Use of probiotics should not be recommended at this time.