Abstract
BACKGROUND: Iron deficiency is prevalent among female athletes, often leading to fatigue, impaired recovery, and decreased performance. Conventional oral iron supplements are associated with poor absorption and negative gastrointestinal side effects, resulting in low adherence. This feasibility trial investigated the tolerability and gastrointestinal effects of an iron-yeast complex (FeSC) supplement in physically active females to assess its potential for further study. METHODS: This single-arm, mixed-methods feasibility trial recruited 14 active females (18-25 years) who consumed FeSC-fortified cookies (40 mg elemental iron) every other day for 14 days. Gastrointestinal symptoms, stress, and recovery were assessed through daily and weekly questionnaires (daily questionnaires: Gastrointestinal Symptoms Questionnaire and Short Recovery and Stress Scale; weekly questionnaires: Patient-Reported Outcomes Measurement Information System (PROMIS) Gastrointestinal Symptom Scale; RESTQ Basic-24). Qualitative data on supplement acceptability were collected post-intervention. Feasibility was evaluated based on recruitment, retention, adherence, and safety criteria. RESULTS: Out of 52 participants who completed our screening questionnaire, 14 (age = 22 SD 2 years; weekly physical activity = 420 SD 140 min/week) met all criteria and completed the intervention. All feasibility criteria were met, including 100% retention, adherence, and questionnaire completion rates. Participants reported good supplement tolerability, with only a few cases of mild, transient gastrointestinal symptoms. A reduction in constipation symptoms compared to baseline and a reduction in diarrhea symptoms on days cookies were consumed compared to days they were not were observed. No serious adverse events occurred. While some participants noted a metallic aftertaste, 57% indicated that they would prefer the supplement in cookie form over traditional iron pills if given the choice. CONCLUSIONS: This study demonstrates the feasibility and tolerability of FeSC supplementation in active females, with potential gastrointestinal benefits. Findings support progression to a larger trial assessing FeSC's impact on iron status and long-term adherence. TRIAL REGISTRATION: ClinicalTrials.gov NCT06285851. Registered on January 30, 2024.