Supplementation with iron can help pre-menopausal women to train longer and harder, according to research published in the American Journal of Clinical Nutrition.
Iron deficiency without anaemia occurs in about 12 per cent of pre-menopausal women in the United States, and may negatively affect adaptation to aerobic training in women by reducing their endurance capacity, the researchers said. They looked at 41 healthy women aged 18-33, all of whom were iron-deficient but not anaemic. They were given either a 50 mg iron supplement (22 subjects) or a placebo (19 subjects) twice daily for six weeks in a randomised, double-blinded trial.
During the last four weeks of the study, they trained five days a week on an ergometric cycle equipped with a heart rate monitor and digital output of cadence and work. They gradually increased their workloads until they were cycling for 10 minutes at 75 per cent and 15 minutes at 85 per cent of their maximum heart rates. Exercise tests were conducted on a cycle ergometer before and after the aerobic training.
The iron-supplemented group experienced twice the improvements in maximal oxygen uptake and respiratory exchange ratio than the placebo group, the researchers said. The women with the most depleted initial iron status experienced the most improvement in their adaptation to aerobic exercise.
The researchers concluded that otherwise healthy women may realise added benefits from their exercise programmes by improving marginal iron deficiency.