IRON DEPLETION WITHOUT ANEMIA AND PHYSICAL PERFORMANCE IN YOUNG-WOMEN

Studies in laboratory animals found that iron deficiency without anemi a decreased oxidative capacity and increased reliance on carbohydrate as the substrate for energy, thereby causing impaired endurance. The p urpose of this cross sectional study was to investigate the relation b etween iron deficiency without anemia and physical performance in heal thy active women aged 19-36 y. Iron-status assessment included determi nation of hemoglobin, hematocrit, transferrin saturation, and serum fe rritin values. Dietary iron intake was assessed by frequency questionn aires and physical activity level was estimated by frequency questionn aires and 2-wk records. Fifteen women with normal iron status and 15 w omen with iron depletion (serum ferritin < 12 mu g/L) were chosen rand omly from a group of 69 nonanemic women and given physical-performance tests, including determinations of maximum oxygen consumption (VO(2)m ax), ventilatory threshold, and delta-efficiency. There were Ilo signi ficant differences between the two groups in body size, body compositi on, physical activity level, dietary iron intake, delta-efficiency, or ventilatory threshold. Compared with the iron-depleted group, the iro n-sufficient group had significantly higher hemoglobin, transferrin sa turation, and serum ferritin values and a significantly greater tenden cy to use iron supplements. When physical activity level and fat-free mass were controlled for, the iron-depleted group had a significantly lower VO(2)max. The difference in VO(2)max was significantly associate d with serum ferritin concentration; hemoglobin value was not a signif icant confounder. Therefore, reduction of VO(2)max in nonanemic women with iron depletion was likely caused by factors related to reduced bo dy iron storage but was unrelated to decreased oxygen-transport capaci ty of the blood.