Effect of yogurt with Bifidobacterium DN-173 010 on salivary mutans streptococci and lactobacilli in young adults

Probiotic bacteria are thought to reduce the risk of disease. Previous studies have suggested that lactobacilli-derived probiotics in dairy products may affect the oral ecology, but the effect of bifidobacteria has not previously been reported. The aim of the present study was to examine whether or not short-term consumption of yogurt containing bifidobacteria would affect the salivary levels of mutans streptococci and lactobacilli in young adults. A double-blind, randomized crossover study was performed and 21 healthy subjects were followed over four periods. During periods 2 and 4 (2 weeks each), they ingested 200 g yogurt containing Bifidobacterium DN-173 010 once daily or a control yogurt without viable bacteria. Periods 1 and 3 were run-in and washout periods, respectively. Salivary mutans streptococci and lactobacilli were enumerated with chair-side kits. A statistically significant reduction (p < 0.05) of salivary mutans streptococci was recorded after the probiotic yogurt consumption, which was in contrast to the controls. A similar trend was seen for lactobacilli, but this decrease failed to reach statistical significance. In conclusion, probiotic bifidobacteria in yogurt may reduce the levels of selected caries-associated microorganisms in saliva.