Improving Iron Levels in Female Endurance, Intermittent, and Power/Strength Athletes Aged 16-35

This clinical trial is designed to evaluate and compare the effects of three oral iron supplementation strategies on iron status, gut microbiota, and athletic performance in young female athletes with suboptimal iron levels. The study compares a low-dose iron supplement, a low-dose yeast-bound iron supplement (Lalmin® Fe10), and a high-dose iron supplement. The primary goal is to identify which iron supplement improves iron status most effectively while minimizing gastrointestinal symptoms and changes to the gut microbiota.

The rationale for the study is based on the high prevalence of iron deficiency among female athletes, especially those involved in endurance and high-intensity sports. Iron plays a key role in oxygen transport, energy production, and recovery, making it essential for optimal athletic performance. However, current supplementation practices often lead to poor compliance due to side effects and low absorption rates. The yeast-bound iron product being tested is hypothesized to improve absorption and tolerability by altering the site of absorption and reducing gastrointestinal distress.

Participants will be biologically female athletes aged 16-35 with suboptimal ferritin (≤50 µg/L), who are competitively trained and meet strict health and fitness criteria. After screening, eligible participants will be randomly assigned to one of three groups and consume their assigned supplement every other day for 12 weeks. Each supplement will be encapsulated to preserve blinding and consistency.

The study involves six in-person visits:

Visit 1 Screening and Consenting:

Study investigators will reach out electronically or by phone to individuals interested in participating in the study. At this time, participants will be informed about the study and eligibility will be confirmed. Iron status will be assessed using ferritin, achieved through a forearm venipuncture. Participants with suboptimal ferritin levels (≤50 µg/L) will be asked to complete a 3-day food record over the following week on non-consecutive days. This food intake data will be used to determine energy availability to ensure participants meet the minimum requirement of \>30 kcal/kg lean body mass. Those who do not meet this requirement will be excluded from further participation.

Visit 2 Baseline Testing (Week 0):

Once inclusionary criteria has been confirmed and met, participants will undergo baseline measures of iron status through a forearm blood draw, they will complete a body composition assessment to assess lean body mass, and participants will complete a cycling-based aerobic fitness test (VO2 max) to characterize their fitness level. Participants will also be sent home with a package with SIMBA capsules, fecal sample collection kit, and collection instructions.