The effect of iron and folate therapy on maximal exercise performance in female marathon runners with iron and folate deficiency

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Abstract
Of the 85 female marathon runners examined in this study, 14 (16%) had serum ferritin levels below 40 ng/ml but only two (2%) had iron deficiency anaemia (haemoglobin below 12 g/dl); 28 (33%) had serum folate levels below 4.8 ng/ml and of these two (2%) had haemoglobin levels below 12 g/dl and 13 (15%) had mean corpuscular volumes greater than 95 fl. One week after treatment with oral folate (5 mg/day) or iron (50 mg of elemental iron/day), serum ferritin and folate levels were normal but maximum oxygen uptake, maximum treadmill running time, peak blood lactate levels and the running speed at the blood ''lactate turnpoint'' were not changed from values measured during an identical test performed 1 week earlier. These parameters were also unchanged in a third exercise test performed after a further 10 weeks of treatment. Serum folate or serum ferritin levels in a control (placebo-treated) group with initially high serum ferritin or folate levels fell with placebo treatment but maximum treadmill running time, maximum oxygen uptake values, peak blood lactate levels and the running speed at the blood ''lactate turnpoint'' were unchanged. We conclude that biochemical evidence of iron and folate deficiency is relatively common in female distance runners; that 1 week of treatment corrects the biochemical evidence of folate and iron deficiency but that such treatment does not influence maximal exercise performance nor does it alter blood lactate levels during exercise. In the absence of iron deficiency anaemia, iron therapy for reduced serum ferritin levels, or folate therapy for low serum folate levels, may not improve maximal treadmill performance even in trained runners. Serum ferritin or folate levels above the normal range are not associated with enhanced maximum oxygen uptake, maximum treadmill performance, lower blood lactate levels during exercise or higher running speeds at the blood ''lactate turnpoint''.