The Role of Probiotics in Improving Menstrual Health in Women with Primary Dysmenorrhoea: A Randomized, Double-Blind, Placebo-Controlled Trial (the PERIOD Study)

Background: Primary dysmenorrhea is associated with poorer quality of life; however, the causal mechanism remains unclear. A vast body of literature supports the use of oral probiotics for relief from the symptoms of endometriosis; however, to our knowledge, no study has prescribed probiotics for primary dysmenorrhea. Objective: The aim of this study is to investigate the effects of 3-month supplementation with oral probiotics on quality of life and inflammatory markers in women with primary dysmenorrhea. Design: Randomized placebo-controlled trial. Methods: A total of 72 patients (36 patients in each arm) were randomized to receive either oral sachets containing 5 billion colony-forming units each of Lactobacillus acidophilus BCMC (BCrobes Microbial Cells) 12130, Lactobacillus casei subsp BCMC 12313, Lactobacillus lactis BCMC 12451, Bifidobacterium bifidum BCMC 02290, Bifidobacterium longum BCMC 02120, and Bifidobacterium infantis BCMC 02129 each or placebo twice daily for 3 months. Main outcome measures were visual analog scale, verbal rating scale, physical and mental health scores using Short-Form 12-Item version 2 questionnaire, frequency of nonsteroidal anti-inflammatory drug use, and changes in inflammatory markers (interleukin-6, interleukin-8, and tumor necrosis factor alpha) before and after treatment. Results: There was no significant difference in the quality of life scores between the probiotic and placebo groups. Both groups showed significant improvement in pain (visual analog scale) and severity (verbal rating scale) scores but the probiotic group had much lower nonsteroidal anti-inflammatory drug use (odds ratio: 0.69, 95% confidence interval: 0.26–1.83) and better mental health scores (mean change: 6.5, p = 0.03 versus 6.1, p = 0.08) than the placebo group. There was a significant confounding effect of nonsteroidal anti-inflammatory drug use on quality of life scores. No significant difference was found in inflammatory cytokines. Conclusion: Tested oral probiotics improved mental health and potentially reduced the use of nonsteroidal anti-inflammatory drugs; however, there was no significant change in inflammatory markers. Further research with a larger sample size is needed to confirm the findings. Registration: This study is registered under ClinicalTrials.gov (NCT04119011).