Findings from an open-label pilot study of 20 adults suggested that supplementation with 15 g/day of yeast mannans was highly tolerable and demonstrated specific modulation of the microbiota and increased stool frequency in a subset of subjects reporting ≤1 stool per day at baseline. The primary aim of this randomized, double-blind, controlled trial is to determine if yeast mannan supplementation at 12 g/day will increase stool frequency in generally healthy adults reporting ≤1 stool per day. Secondary aims will determine the effect of yeast mannans on intestinal transit time, gastrointestinal symptoms, fecal microbiota composition, and urinary and fecal metabolomics.

Inclusion Criteria:

• Adults who report a stool frequency of ≤ 1 per day.
• Able to provide written informed consent in English.
• Willingness to consume 1 supplement (12 g of yeast mannans or control) daily for 28 days.
• Willingness to maintain their usual diet and physical activity patterns throughout the study and refrain from the consumption of any yeast-based foods (e.g. Marmite or Vegemite) or yeast extract supplements.
• Willing to comply with study procedures, including stool and urine colle

Exclusion Criteria:

• Stool frequency of < 3 per week
• Yeast allergy
• Vegan dietary pattern
• Self-reported kidney disease
• Elite athletes or long-distance runners
• Use of antibiotic drugs within 1 month of screening
• Current use of laxatives or antidiarrheal medications
• Use of other investigational products within 3 months of the screening
• Previously or currently being treated for intestinal diseases or conditions, including irritable bowel disease (i.e., IBS-D or IBS-mixed), Crohn's disease, ulcerative colitis, celiac disease, or gastrointestinal cancer.
• Previous gastrointestinal surgery (e.g., gastric bypass, fundoplication, bowel resection).
• Current cancer treatment.
• Currently pregnant.