Iron supplements may boost female physical performance: Meta-analysis

Iron supplements may boost female physical performance: Meta-analysis

Scientific evidence from 22 randomized controlled trials indicates that daily iron supplements may significantly boost exercise performance for women.

Supplements of iron were associated with increases both maximal and sub-maximal exercise performance, as demonstrated by increases in oxygen consumption (VO2 max) and a lower heart rate, respectively, according to findings published in the Journal of Nutrition.

“These benefits are clearest in iron-deficient and trained women,” wrote the authors from the University of Melbourne (Australia), the University of Oxford (UK), The Alfred Hospital in  Melbourne, the University of Adelaide (Australia), Monash Health (Australia), and The Micronutrient Initiative (Canada).

“Our findings have implications for clinical management of patients, nutritional optimization for athletes, and rationale and design of public health anemia control programs. These results also begin to define the physiologic deficits induced by iron deficiency.

“To our knowledge, this is the first published meta-analysis to provide evidence of beneficial effects of iron supplementation on physical performance.”

Iron and physical performance

Iron deficiency is a risk for many women of reproductive age, explained the authors, because of menstrual blood losses. “Female athletes are at particular risk,” they wrote, “because of diets deficient in iron, increased losses due to gastrointestinal bleeding, and reduced iron absorption due to subclinical inflammation.”

Data from both animal and human studies have suggested that low iron levels can impair physical exercise performance.

Almost half a billion non-pregnant women are anemic around the world, with 50% of this anemia thought to be responsive to iron

In order to investigate if iron supplementation can affect exercise performance in women of reproductive age, the authors performed a systematic review and meta-analysis. Scientific databases were searched for eligible trials, and the identified 22 with extractable data.

Results showed that iron supplements were associated with both an increase in maximal oxygen consumption (VO2 max) and lower heart rates.

“Our findings indicate that prevention and treatment of iron deficiency could improve performance in female athletes who compete in a wide range of sports requiring either or all of endurance, maximal power output, and strength,” they wrote. “The magnitude of increase in relative VO2 max from iron [0.82–3.88 mL/(kg.min)] is in the range of improvements that can be achieved by exercise training.”

“Improvements in physical performance from iron supplementation may extend to broader benefits. For example, [one study from China] showed that female cotton-mill workers randomly assigned to take iron experienced improved productivity and earnings and also had reduced [heart rate] during work compared  with women in the control group,” they added.

“Given the beneficial effect from iron supplementation in women in whom baseline iron or anemia status was not measured, our data support, in populations in which iron deficiency and anemia are highly prevalent, implementation of public health measures to alleviate the burden of iron deficiency (such as daily or intermittent iron supplementation, staple food fortification, and deworming) and, in settings in which iron deficiency is less prevalent, clinical measures to prevent, detect, and treat iron deficiency in individuals at risk, especially athletes.”

Source: Journal of Nutrition
Published online ahead of print, doi: 10.3945/​jn.113.189589
“Iron Supplementation Benefits Physical Performance in Women of Reproductive Age: A Systematic Review and Meta-Analysis”
Authors: S-R. Pasricha, M. Low, J. Thompson, A. Farrell, L-M. De-Regil

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