Supplemental Iron Improves Submaximal Exercise Performance in Non-anemic Iron Depleted Women
Condition: Iron Deficiency (Without Anemia)
MeSH terms: Iron Deficiencies
Study type: Interventional

Summary: 
      The specific aims of the current study were: 1) To determine the prevalence of IDNA in a
      sample of Mexican women of reproductive age and 2) To determine how iron supplementation in
      IDNA women influences physical work capacity during submaximal exercise . The researchers
      hypothesized that marginally iron depleted women will have improved physical work capacity
      during submaximal intermittent exercise tests after dietary iron supplementation. However, no
      improvement in peak maximal oxygen consumption after dietary iron supplementation because
      they will remain non-anemic.
    

Detailed description: 
      Recent estimates of the prevalence of anemia among non-pregnant Mexican women of reproductive
      age range from 15 percent for a nationally representative sample from the 1988 National
      Nutrition Survey to 29 percent for low socioeconomic women from the PROGRESA baseline survey
      of 1998 (Mexican Ministry of Health, unpublished report). The cause of most of this anemia is
      iron deficiency. It can be assumed that time between 15 and 30 percent of Mexican women also
      experience iron deficiency without also experiencing anemia. In some studies of anemic women,
      iron deficiency has been shown to result in reduced physical performance as measured by
      VO2max (the oxygen consumption at maximum physical exertion), presumably due to reduced
      oxygen (02) transport related to the reduced hemoglobin (Hb) concentration. However, no
      effects of iron deficiency have been shown on VO2max in women who were not anemic. Given that
      Hb concentration is not reduced in iron deficient non anemic women, it is expected that
      VO2max remains unaffected. However, this less severe form of iron deficiency may still affect
      physical performance. The important role of iron in the synthesis of many of the enzymes
      involved in oxidative metabolism suggests that moderate levels of iron deficiency may impair
      muscular energy transformation at levels of exertion that are not as severe as those
      reflected in VO2max. The choice of the appropriate sub maximal physical performance test is
      therefore critical to successful demonstration of the effects of moderate iron deficiency on
      response to exercise stress.

      In this study the investigators proposed to test the effects of iron deficiency on physical
      performance using a randomized double blind design that assigns marginally iron depleted,
      physically active women between 18 and 45 years to two treatments. One half of the women will
      be randomly assigned to a group that receives a daily oral iron supplement (20 mg of
      elemental iron as slow release ferrous sulfate) while the remaining women received a placebo.
      Investigators anticipated that iron supplementation would replete iron body stores in all
      women and increase Hb only in those who are marginally anemic. Investigators tested the
      physical performance response to iron treatment with two exercise tests. It was hypothesized
      that VO2max would not be affected by iron supplementation. A graded submaximal exertion test
      (30 60% of VO2max) to estimate energy expenditure (EE), gross efficiency (GE), and net
      efficiency (NE) was administered to test for an increase in work efficiency due to iron
      supplementation.

      This study has important implications for the definition of dietary iron requirements in this
      segment of the Mexican population. The physical performance test used in this study (EE, GE,
      and NE), while well recognized, have never been applied to this type of research question nor
      has it been examined in relation to endurance performance in Mexican women. Investigators
      believe that previous reliance on the VO2max test to measure performance has biased
      conclusions toward concern only for the anemic subject, while the less severe forms of iron
      deficiency have been considered benign.

      This study, if successful in supporting the stated hypotheses, will serve as further confirm
      the deleterious effects of iron deficiency without anemia and justify future research on more
      practical measures of performance related to female economic productivity and time and effort
      allocated to child care and household responsibilities.
    

Intervention name(s): Placebo; Ferrous sulfate
Intervention type(s): Dietary Supplement; Dietary Supplement
Intervention description(s): 100 mg lactose per day for 6 weeks; 20 mg per day of elemental iron for 6 weeks
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Outcomes Assessor)
Primary purpose: Basic Science
Keywords: iron deficient non-anemic; supplementation; randomized control trial; submaximal intermittent exercise; serum ferritin; body iron