Iron Supplements Boost Physical Performance in Women

Steven Fox

April 16, 2014

Daily iron supplementation can boost physical performance in women of reproductive age (WRA), according to findings from a new review of the literature. The researchers who conducted the study said their findings provide a strong rationale for preventing and treating iron deficiencies among women.

The study, by Sant-Rayn Pasricha, PhD, from the Department of Medicine, University of Melbourne, Australia, and colleagues, was published online April 9 in the Journal of Nutrition.

Dr. Pasricha and coinvestigators note that WRA are at heightened risk for iron deficiency because of menstrual blood loss. Female athletes may be particularly vulnerable because of diets deficient in iron, blood loss caused by gastrointestinal bleeding, and malabsorption of iron because of subclinical inflammation.

The problem is also common among low- and middle-income women and women in developing nations, who often have access only to foods with poor nutritional value. Parasitic infections also exact a toll in that group.

Trials looking into iron supplementation and exercise performance have generally involved relatively small numbers of patients and have arrived at differing findings. "This limits the capacity of primary and specialist clinicians and policymakers to anticipate potential benefits when considering strategies to prevent and treat iron deficiency," the authors write. "Therefore, we performed a systematic review and meta-analysis of [randomized controlled trials] to evaluate the effects of daily iron supplementation on physical performance in WRA."

After screening thousands of studies from a variety of databases, the authors identified 22 that met inclusion criteria: controlled trials that measured exercise outcomes in WRA randomly assigned to receive daily oral iron supplementation or control. Potential for bias was present in most of the studies; only 3 were considered at low risk.

The researchers report that iron supplementation boosted maximal exercise, as confirmed by increases in maximal oxygen consumption (VO2; for relative VO2 max, mean difference [MD] was 2.35 mL/kg · minute [95% confidence interval (CI), 0.82 - 3.88; P = .003; 18 studies]; for absolute VO2 max, MD was 0.11 L/minute [95% CI, 0.03 - 0.20; P = .01; 9 studies]; and for overall VO2 max, standardized MD was 0.37; 95% CI, 0.11 - 0.62; P = .005; 20 studies]).

Supplementation also improved submaximal exercise performance, which the researchers confirmed by reductions in heart rate (MD, −4.05 beats per minute; 95% CI, −7.25 to −0.85; P = .01; 6 studies) and proportion of VO2 max (MD, −2.68%; 95% CI, −4.94 to −0.41; P = .02; 6 studies) needed to achieve defined workloads.

The researchers conclude, "Our data establish evidence of a beneficial effect from iron supplementation on exercise performance in women. Effect estimates can be used to determine the expected benefit to individual women and perhaps populations from alleviation of iron deficiency."

They add that the data might also be used as an aid in establishing and maintaining iron deficiency prevention programs, as well as designing future randomized control trials.

Dr. Pasricha was supported by a Victoria Fellowship by the Government of Victoria, a CRB Blackburn Scholarship by the Royal Australasian College of Physicians, an Overseas Research Experience Scholarship by the University of Melbourne, a National Health and Medical Research Council CJ Martin Early Career Fellowship, as well as an unrestricted research grant from Vifor Pharma. The other authors have disclosed no relevant financial relationships.

J Nutrition. Published online April 9, 2014. Abstract

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