Menstrual pain is mainly divided into primary dysmenorrhea and secondary dysmenorrhea, the former is caused by menstrual uterine muscle movement; the latter is caused by certain diseases, such as Endometriosis, Uterine fibroids and Pelvic inflammatory disease. Menstrual pain has been a troubling issue for many women. The most common type of menstrual pain is at the lower abdomen. For some girls, menstrual pain is accompanied by nausea, diarrhea, fatigue, headache, flatulence, etc.

In addition to menstrual pain, Premenstrual syndrome (PMS) is also one of the problems that affect women's physical and mental health. PMS, as the name suggests, these symptoms appear before menstruation. During the periods, the symptoms will gradually disappear and before the next menstruation it will appear again.

About 80% women in Taiwan have experienced with menstrual pain or premenstrual discomfort. It affects the physical, psychological and social status of most women, and the degree of menstrual pain can also affect mood, sleep quality,school and work efficiency. Although there are many ways to relieve menstrual pain, hot compresses or oral painkillers, contraceptive pills, etc., but these medications are not without side effects.

Probiotics are defined as live microorganisms that, in sufficient quantities, benefit the health of the host. They are mainly bacteria that produce lactic acid, including Lactobacilli, Bifidobacteria, and Saccharomyces boulardii. Most studies have pointed out that probiotics can reduce the severity of gastrointestinal symptoms. Some studies have also pointed out that probiotics can improve physical and psychological functions, such as depression and sleep quality. In addition, animal experiments have shown that probiotics can regulate GABA in mice A and GABA B receptor expression to alter mood.

This study aims to explore whether probiotic supplementation can improve menstrual pain and menstrual discomfort symptoms. If these common menstrual problems can be improved by probiotics, it will be a great significance to improve the quality of life of women. The trial lasts for 8 menstrual cycles, including 2 menstrual cycles in the screening period, 4 menstrual cycles in the test period and 2 menstrual cycles in the follow-up period. This trial will performed in China Medical University Hospital.

Inclusion Criteria:

• Female aged between 20 and 65 years.
• Regular menstrual cycles.
• During the last three menstrual periods, self-reported dysmenorrhea with a pain score ≥ 3 on the Numeric Rating Scale (NRS).
• Able to use effective contraception during the study period.
• Willing to participate in the study and has signed the informed consent form.

Exclusion Criteria:

• Planning to become pregnant, currently pregnant, or in the postpartum stage with menstruation not yet resumed.
• Postmenopausal women.
• Irregular menstrual cycles (cycle length < 21 days or > 40 days).
• Currently taking any psychiatric medications, oral contraceptives, menstrual regulation drugs, weight-loss drugs, or antibiotics.
• Consumption of probiotic-related products within the past 1 month (including drops, tablets, capsules, powder, or yogurt and fermented milk products).