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Prevalence of Iron Deficiency

Effect of Iron Supplementation on Endurance Performance in Iron Deficient Trained Males and Females. United States Females: 11-13% Males: < 1%. Athletes Basketball Players (Dubnov & Constantini 2004) 35% Female 15% Male Various Sports (Malczewska et al. 2001) 26% Female 11% Male

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Prevalence of Iron Deficiency

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  1. Effect of Iron Supplementation on Endurance Performance in Iron Deficient Trained Males and Females

  2. United States Females: 11-13% Males: < 1% Athletes Basketball Players (Dubnov & Constantini 2004) 35% Female 15% Male Various Sports (Malczewska et al. 2001) 26% Female 11% Male Endurance Athletes (Malczewska et al. 2000) 26% Female Prevalence of Iron Deficiency

  3. Maximal Exercise Iron deficiency without anemia was not found to have an affect on aerobic capacity. Endurance Exercise Animal studies reduced in iron-deficient non-anemic rats. (Davies1984, Finch1976, Zinker1993) Human studies No correlation between reduced iron status and endurance capacity. (Klingshirn 1992, Newhouse 1989, LaManca,1993) Reduced endurance capacity due to iron deficiency shown by higher energy expenditures during submaximal workloads and/or shortened time to fatigue. (Brutsaert 2003, Hinton 2000, Zhu 1998, LaManca 1992, and Rowland 1987) Effects of Iron Deficiency on Exercise Performance

  4. Purpose To determine the effect of iron supplementation on iron status and endurance capacity in iron-deficient non-anemic, trained males and females

  5. Iron Status Baseline Post-Supplement Iron Status Iron supplementation, wks 1-6 Wk 1 Wk 2 Wk 3 Wk 4 Wk 5 Wk 6 VO2max VO2max Submax Submax Study Design Iron Status Screening • Randomized, double-blind placebo controlled trial • Iron Supplement: 30mg elemental iron as ferrous sulfate

  6. Iron Status Hb Hct sFer sTfR Subjects Recreationally trained (60 min, 3 days/wk, 6 months +) Females & Males 18-40 yrs Methods • Subject Questionnaires • 3-day diet • Physical activity logs

  7. Exercise Testing • VO2max Test • Max VO2, HR, RER, • VT • 60-min submax test at 60% VO2max • Avg RER • Avg HR • Energy Expenditure (kcal) • Workload (watts) • Efficiency (kcal/watt)

  8. Two-way ANOVA (GxT) One-way ANOVA Multiple linear regression Initial iron status x group Pearson Correlations Significance level set at p0.05 Means ± SE Statistical Analysis

  9. Iron Group 9 Females, 1 Male Age: 28.1 ± 1.6 yrs. Wt: 61.7 ± 2.1kg BF: 21.6 ± 1.4 % PA: 3092 ± 590 kcal/wk (pre) 3156 ± 555 kcal/wk (post) Iron: 17.5 ± 1.7 mg (pre) 19.8 ± 1.4 mg (post) Placebo Group 8 Females, 2 Males Age: 27.7 ± 1.4 yrs. Wt: 67.8 ± 3.7 kg BF: 21.2 ± 1.2 % PA: 2561 ± 813 kcal/wk (pre) 2418 ± 660 kcal/wk(post) Iron: 19.2 ± 3.7 mg (pre) 17.6 ± 2.5 mg (post) Subjects

  10. Serum Ferritin G x T p = .007 G x T p = 0.011

  11. sTfR & sTfR/log sFer Index G x T p = 0.072

  12. Ventilatory Threshold G x T p = 0.012 G x T p = 0.042

  13. Effect of Initial Iron Status on Response to Supplementation

  14. Heart Rate T p = 0.023

  15. Workload & Efficiency T p = 0.048 T p = 0.049

  16. Relationship between sFer & submax RER p = 0.055 r = -0.189

  17. Summary • Iron supplementation • Improved iron status • Maintained VT, with no effect on VO2max • Increased energetic efficiency during submaximal exercise • Initial iron status modified the change in VT after iron supplementation • Changes in sFer correlated with RER

  18. Conclusion Improved iron status in iron-deficient individuals enhances or maintains aerobic function

  19. Acknowledgments Dr. Pam Hinton Dr. Tom Thomas Scott Rector MU Dept. of Nutritional Sciences University of Missouri Alumni Association Gatorade Sports Science Institute

  20. Factors Affecting Iron Status of Physically Active Individuals • Gastrointestinal bleeding (0.5 to 2 mg iron/day) • Hemolysis of red blood cells “foot strike hemolysis” • Sweating • Diet • Menstruation (0.5 to 0.6 mg mg iron/day) •  iron need ? Estimated iron loss in endurance training athletes is on average: 1.5-1.7 mg/day for men and 2.2-2.3 mg/day for women. (Haymes and LaMaca Iron Loss in runners during exercise. Sports Med. 1989)

  21. How does iron deficiency affect exercise performance? • Hemoglobin – delivery of O2 to cells • Myoglobin – transports & stores O2 in muscle • Iron dependent enzymes – • Cytochromes – oxidative metabolism • Iron functions in delivery of oxygen to tissues and facilitates the use of oxygen at the cellular level.

  22. Iron Status Screening # of Subjects

  23. Iron Indicators sFer • Indicator of storage iron • Acute phase protein •  with infection or inflammation • Exercise induces inflammatory-like response sTfR • New marker of iron status • Indicator of functional iron • Not affected by inflammatory reactions • Up-regulated when iron stores are depleted sTfR/log ferritin index • More sensitive for borderline cases • Stages of iron deficiency are detectable using this index

  24. VO2max Test

  25. Ventilatory Equivalents  Determination of VT 35 30 25 VE/VO2 20 VE/VCO2 15 0 1 2 3 4 5 6 7 8 9 10 Time (min)

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