A review of probiotic supplementation in healthy adults: helpful or hype?

Probiotic supplements have a positive impact on several health outcomes. However, the majority of published studies have focused on populations with specific health pathologies. Therefore, this study reviewed the current literature on the health effects of probiotic consumption in "healthy adults." The findings from this review may help guide consumers, researchers, and manufacturers regarding probiotic supplementation. Relevant literature published between 1990 and August 2017 was reviewed. Studies were included if they were experimental trials, included healthy adults, used live bacteria, and had accessible full-text articles published in English. Included studies were classified according to common foci that emerged. Forty-five studies were included in this review. Five foci emerged: gut microbiota changes (n = 15); immune system response (n = 16); lipid profile and cardiovascular disease risk (n = 14); gastrointestinal discomfort (n = 11); and female reproductive health (n = 4). Results suggest that probiotic supplementation in healthy adults can lead to transient improvement in gut microbiota concentration of supplement-specific bacteria. Evidence also supports the role of probiotics in improving immune system responses, stool consistency, bowel movement, and vaginal lactobacilli concentration. There is insufficient evidence to support the role of probiotics to improve blood lipid profile. Probiotic consumption can improve in the immune, gastrointestinal, and female reproductive health systems in healthy adults. However, this review failed to support the ability of probiotics to cause persistent changes in gut microbiota, or improve lipid profile in healthy adults. The feasibility of probiotics consumption to provide benefits in healthy adults requires further investigation.