The researchers gave 219 women in eight-week basic combat training (BCT) either a placebo or supplements containing 100 mg ferrous sulphate.
Those given the iron supplements recorded improved scores for two-mile running tests and cognitive performance.
“Iron supplementation resulted in improved (P: 0.05) vigor scores on the Profile of Mood States post-BCT and in faster running time (P: 0.05) in volunteers reporting to BCT with iron deficiency anemia,” the researchers noted.
The randomised, double-blind, placebo-controlled trial also found red blood cell distribution width and soluble transferrin receptor were elevated and serum ferritin was lowered post-BCT.
“Future efforts should identify and treat female soldiers or athletes who begin training regimens with iron deficiency or iron deficiency anaemia,” the researchers concluded.
Research indicates iron deficiency (ID) affects up to 16 and 21 per cent of premenopausal women in the US and UK respectively, and it is thought iron deficiency may affect up to 50 per cent of the world’s population, with the condition reaching pandemic status in the developing world.
But in the western world it is a very female-centric problem. “Premenopausal women are at the greatest risk of ID because suboptimal iron consumption and menstrual bleeding lead to negative iron balance,” wrote the researchers from the US Army Research Institute of Environmental Medicine.
“Furthermore, premenopausal women who engage in regular physical activity may be at even greater risk of poor iron status because physical activity appears to have a negative effect on iron stores.”
About 15 per cent of the US military are women, amounting to 341,000 individuals.
The researchers said the effect of ID with anaemia (IDA) is well-documented and leads to reduced ability to do physical work. While the effects of ID were less well-documented, some results have shown, “impaired aerobic adaptation and endurance capacity in women”.
Supplementation with iron could reduce the, “longitudinal decrement in iron status previously observed in female soldiers,” the researchers said.
The women in the study took their iron supplements before breakfast and took no other multivitamins or mineral supplements during the eight-week trial.
The BCT involved road marching, distance running and sprinting, muscle strength training, calisthenics, exercises, sit-ups and push-ups, rappelling, obstacle courses, prolonged standing in formation, and didactic classroom instruction.
The researchers noted the increase in physical strain that is common among female athletes taking BCT for the first time may lead to increases in pro-inflammatory cytokines which subsequently affect the synthesis of hepcidin by the liver, which affects iron levels.
One study observed increased urinary hepcidin excretion in female athletes following a marathon.
Other potential causes for ID and IDA included gastrointestinal bleeding, increased whole-body iron turnover, exercise-induced hematuria or iron loss through sweat.
Meat consumption did not change during the eight-week BCT despite it being a good source of iron.
The American Journal of Clincial Nutrition
‘Randomized, double-blind, placebo-controlled trial of iron supplementation in female soldiers during military training: effects on iron status, physical performance, and mood’
Authors: James P McClung, J Philip Karl, Sonya J Cable, Kelly W Williams, Bradley C Nindl, Andrew J Young, and Harris R Lieberman