Purpose of Review: Probiotics are promising remedial treatments for symptoms of small intestine (SI) diseases and promoters of overall good health. Probiotics play an important role in supporting a healthy SI microbiome (eubiosis), and in preventing establishment of unhealthy microbiota. SI eubiosis promotes optimal nutrient uptake, and optimal nutritional status maintains a healthy SI, reducing the likelihood of SI diseases. It is important to understand the advantages and limitations of probiotic therapies. Recent Findings: Microbial dysbiosis decreases the capacity of the small bowel to utilize and absorb dietary compounds. In some studies, probiotic supplements containing lactic acid bacteria and Bifidobacterium have been demonstrated effective in supporting beneficial microbes in the SI while improving barrier integrity and reducing nutrient malabsorption and SI disease-related pathology. Summary: Strain-specific probiotic therapy may be a natural and effective approach to restoring SI barrier integrity and eubiosis, resulting in improved nutrient absorption and better health, including reducing the incidence of and severity of SI diseases.

Background: Little is known about how the menstrual cycle affects gastrointestinal function and self-reported stress in young, healthy women taking oral contraceptives (OC). This study prospectively characterized gastrointestinal function and symptoms on each day throughout the menstrual cycle. Methods: Healthy women aged 18–35 years (n = 78) who took OC participated in the 5-week observational study. Stool frequency, self-reported stress, stool form measured by the Bristol Stool Form Scale (BSFS), and gastrointestinal symptoms measured by a modified version of the Gastrointestinal Symptom Rating Scale (GSRS) were assessed daily. GSRS scores were reported (1 = no discomfort at all, 7 = very severe discomfort) and were averaged for individual syndrome scores or summed for the total score. The validated, weekly version of the GSRS was completed at two time points to reflect menstruation and 1 week prior to menstruation (n = 72). Outcomes were analyzed in linear mixed models with the Dunnett’s post hoc test against day 1 of menstrual bleeding or with nonparametric tests. Results: Daily stress (P = 0.0018), BSFS score (P = 0.0493), stool frequency (P = 0.0241), abdominal pain (P < 0.0001), diarrhea (P = 0.0022), constipation (P = 0.0446), reflux (P = 0.0193), and indigestion (P < 0.0001) all varied significantly by the day of the menstrual cycle. Dunnett’s post hoc tests showed that scores (mean ± SEM) on the first day of bleeding (day 1) for daily abdominal pain (2.6 ± 0.2), diarrhea (1.7 ± 0.1), and indigestion (2.1 ± 0.2) symptoms were higher than scores on all other days of the menstrual cycle (P < 0.05) with scores not on day 1 falling under 1.5, or between no discomfort at all and slight discomfort. Reflux, stool frequency, BSFS, self-reported stress, and constipation were higher on day 1 (P < 0.05) than on 12, 8, 6, 4, and 2 other days of the menstrual cycle, respectively. The median (IQR) GSRS score was higher during the week of menstruation than the week prior to menstruation for diarrhea [1.50 (1.00–2.33) vs 1.33 (1.00–2.00), P = 0.002] and abdominal pain [2.00 (1.33–2.67) vs 1.67 (1.33–2.33), P = 0.011] syndrome scores. Conclusion: Bowel habits appear to vary across the menstrual cycle and suggest more gastrointestinal discomfort on day 1 of menstrual bleeding in healthy women taking OC. Future interventional studies could identify ways to improve gastrointestinal symptoms in healthy women during menstruation.

This randomized, placebo-controlled, double-blind, parallel trial investigated whether generally healthy adult, nonelite runners would have a greater time-to-exhaustion during submaximal treadmill running with probiotic versus placebo supplementation. It was hypothesized that the probiotic would impact training progression by reducing gastrointestinal (GI) and cold/flu symptoms. Participants who typically ran ≥24 km/week, ran or cross-trained 3–5 days per week, and had a maximal oxygen intake (V̇O₂ max) in the 60–85th percentile were enrolled. V̇O₂ max was used to establish individualized workload settings (85% of V̇O₂ max) for the submaximal endurance tests at baseline and following 6 weeks of supplementation with a probiotic ( Lactobacillus helveticus Lafti L10, 5×10⁹ CFU/capsule/day) or placebo. Participants self-reported GI and cold/flu symptoms and physical activity via daily and weekly questionnaires. Outcomes were tested using a linear model to determine if mean response values adjusted for baseline differed between groups. Twenty-eight participants ( n = 14/group), aged 25 ± 5 years (mean ± SD) with a body mass index of 23 ± 3 kg/m², completed the study. At the final visit the probiotic group had a lower time-to-exhaustion versus the placebo group ( P = 0.01) due to an increase in time-to-exhaustion with the placebo (1344 ± 188 to 1565 ± 219 s, P = 0.01) with no change with the probiotic (1655 ± 230 to 1547 ± 215 s, P = 0.23). During the intervention, the probiotic group completed fewer aerobic training sessions per week ( P = 0.02) and trained at a lower intensity ( P = 0.007) versus the placebo group. Few GI and cold/flu symptoms were reported with no differences between groups. Time-to-exhaustion increased in the placebo group, possibly due to differences in training habits.

Introduction: For many women, uncomfortable and stressful symptoms accompany the menstrual cycle each month, sometimes in a debilitating manner. Previous studies have reported that gastrointestinal symptoms in healthy women significantly differ by the day of the menstrual cycle, but few studies have assessed interventions intended to minimize these symptoms. Probiotics supplements have been shown to attenuate gastrointestinal symptom severity as well as self-reported feelings of stress in various populations. This study evaluates the effect of a probiotic on abdominal pain and gastrointestinal symptoms in healthy women who take an oral contraceptive, have regular menses, and typically experience these symptoms during menstruation with the primary aim being change in abdominal pain intensity related to the menstrual cycle with probiotic versus placebo supplementation. Methods and analysis: In this randomized, double-blind, placebo-controlled parallel study, participants will receive either a probiotic or placebo supplement. Participants will begin answering questionnaires approximately 7 days before the start of menstruation (i.e., active bleeding), and 3 days later, they will begin consuming the study supplement for 8 weeks. The questionnaires administered will collect data about abdominal pain severity (primary outcome) and duration related to the menstrual cycle, digestive health, dietary intake, stress, and digestion-associated quality-of-life. A subgroup of women will provide weekly vaginal swabs and stool samples to examine the effect of the probiotic supplement on microbiota composition and diversity for exploratory purposes. Two-sided tests using a linear model and a type I error rate of α = 0.05 will be employed to test all hypotheses. Continuous variables will be presented as means with standard errors and categorical variables, as counts or proportions. Ethics and dissemination: This study was reviewed and approved by the University of Florida Institutional Review Board 01. Written informed consent will be obtained from all participants prior to any study activities. Study findings will be disseminated at scientific conferences and publication in the trial registry or in a peer-reviewed journal. Any protocol amendments will be reported in the final manuscript of this study. Trial registration: ClinicalTrials.gov NCT04457401. Registered prospectively on 07 July 2020. The trial was completed in December of 2021. Protocol version: V4.0 (11-04-2020) Trial status: Currently recruiting. Recruitment began in November 2020 and extend until December 2021.