Improvement of constipation and liver function by plant-derived lactic acid bacteria: a double-blind, randomized trial.

OBJECTIVE Lactic acid bacteria (LAB) contribute to human health; however, the probiotic properties vary among strains classified into the same species. The primary objective of this study was to evaluate the effects of yogurts made by different types of LAB on the gastrointestinal system. The yogurts were also evaluated by measuring serum lipid contents and liver functional indicators as a secondary objective. METHODS Healthy human adults (n = 68) with some complaints with regard to intestinal health, including constipation and diarrhea, were randomly assigned to receive one of three types of yogurt in a double-blind manner: type A, a yogurt made by plant-derived LAB (mainly Lactobacillus [Lb.] plantarum SN35N); type B, a yogurt made by plant-derived LAB (mainly Lb. plantarum SN13T); and type C, a yogurt made by animal-derived LAB (mainly Lactococcus lactis A6 and Streptococcus thermophilus 510) as a control. The subjects consumed 100 g of yogurt daily for 6 wk. Data were collected from clinical visits at 2-wk intervals and by diaries used to record defecation and health conditions. RESULTS Drastic and constant increments of defecation frequency in subjects with constipation were observed with type A and B yogurts but not with type C yogurt. Type B and C yogurts resulted in decreases in total and low-density lipoprotein cholesterol. The serum concentrations of liver functional parameters were improved by the type B yogurt (12-25% reduction). CONCLUSION The present study suggests that Lb. plantarum SN13T exhibits a superior probiotic effect on constipation in addition to improving the serum lipid contents and liver function.