The study is a randomized, double-blind, crossover, placebo-controlled clinical intervention trial to test the effects of a commercial Bacillus (Shouchella) clausii probiotic compared to a placebo on gastrointestinal symptoms.

Prospective participants are pre-qualified by email screening and attended an in-person study visit at Colorado State University's Food and Nutrition Clinical Research Laboratory (FNCRL) in the Department of Food Science and Human Nutrition. During the initial visit, participants signed the Consent Form after the nature of the procedure had been fully explained to them. Their eligibility is confirmed by taking anthropometric measurements of height (cm) and weight (kg) to calculate BMI and by completing a written medical health questionnaire to determine medical history and current medication use. Eligible participants are then assigned sequentially to a study code (MS01, MS02, etc.), and codes were pre-assigned to intervention sequences using a random number generator in Microsoft Excel. For the initial clinic visit (and subsequent visits), participants are fasted for at least 8 hours and asked to abstain from alcohol use for at least 12 hours prior to clinic visits. They were also instructed to refrain from taking any non-prescription medications for 24 hours or dietary supplements for 12 hours before their visits. At the initial visit, a venous blood sample was collected, and participants filled out several assessment forms/questionnaires: GI Health Appraisal Questionnaire, GI Symptom Rating Scale (GSRS), GI Quality of Life Questionnaire (IBS-QOL Questionnaire) 7-day Physical Activity Recall, Positive and Negative Affect Schedule, and Perceived Stress Scale.

Inclusion Criteria:

• Age 18-75
• BMI 18-34.9
• self report as healthy
• consistent Mild to Moderate gastrointestinal distress (determined by a functional GI screen)

Exclusion Criteria:

• <18 or >75
• BMI <18 or >34.9
• antibiotics within two months
• probiotic/prebiotic supplements within two weeks prior to the screening process
• pregnant or breastfeeding
• taking medications that influence study endpoints of the study (i.e., statins, metformin, nonsteroidal anti-inflammatory drugs, and monoamine oxidase inhibitors)
• a current diagnosis of cancer, liver or kidney disease, metabolic disorders, and GI diseases (Celiac disease, inflammatory bowel disease, and peptic ulcer disease)

Capsules for the intervention and placebo were produced and coded by ADM Deerland and they held the blinding codes until after the primary outcomes were analyzed.