title: Iron supplementation improves endurance after training in iron-depleted, nonanemic women. Marginal iron deficiency without anemia impairs aerobic adaptation among previously untrained women. Tissue iron deficiency without anemia impairs adaptation in endurance capacity after aerobic training in previously untrained women. Functional consequences of iron supplementation in iron-deficient female cotton mill workers in Beijing, China. Iron depletion without anemia and physical performance in young women. Iron supplementation improves progressive fatigue resistance during dynamic knee extensor exercise in iron-depleted, nonanemic women. Iron status in exercising women: the effect of oral iron therapy vs increased consumption of muscle foods. Clinical evaluation of iron treatment efficiency among non-anemic but iron-deficient female blood donors: a randomized controlled trial Effects of iron repletion on blood volume and performance capacity in young athletes. Improvement in iron deficiency anemia through therapy with ferric ammonium citrate and vitamin C and the effects of aerobic exercise. Effect of iron supplementation on endurance capacity in iron-depleted female runners. Iron repletion decreases maximal exercise lactate concentrations in female athletes with minimal iron-deficiency anemia. Iron supplementation maintains ventilatory threshold and improves energetic efficiency in iron-deficient nonanemic athletes Effect of an iron supplement on body iron status and aerobic capacity of young training women Response of serum transferrin receptor to iron supplementation in iron-depleted, nonanemic women. Effects of iron repletion on VO2max, endurance, and blood lactate in women. Iron supplementation and running performance in female cross-country runners. Hepcidin is the major predictor of erythrocyte iron incorporation in anemic African children Effects of iron supplementation in female athletes with low serum ferritin concentration. The effect of iron therapy on the exercise capacity of nonanemic iron-deficient adolescent runners. Randomized, double-blind, placebo-controlled trial of iron supplementation in female soldiers during military training: effects on iron status, physical performance, and mood. The effects of hemoglobin supplements on maximal oxygen uptake in females. The effects of prelatent/latent iron deficiency on physical work capacity. Worker productivity and the nutritional status of Kenyan road construction laborers. Effects of long-term moderate exercise on iron status in young women.
abstract: Our objective was to investigate the effects of iron depletion on adaptation to aerobic exercise , assessed by time to complete a 15-km cycle ergometer test . Forty-two iron-depleted ( serum ferritin < 16 microg/l ) , nonanemic ( Hb > 12 g/dl ) women ( 18 - 33 yr old ) received 100 mg of ferrous sulfate ( S ) or placebo ( P ) per day for 6 wk in a r and omized , double-blind trial . Subjects trained for 30 min/day , 5 days/wk at 75 - 85 % of maximum heart rate for the final 4 wk of the study . There were no group differences in baseline iron status or in 15-km time . Iron supplementation increased serum ferritin and decreased transferrin receptors in the S compared with the P group . The S and P groups decreased 15-km time and respiratory exchange ratio and increased work rate during the 15-km time trial after training . The decrease in 15-km time was greater in the S than in the P group ( P = 0.04 ) and could be partially attributed to increases in serum ferritin and Hb . These results indicate that iron deficiency without anemia impairs favorable adaptation to aerobic exercise BACKGROUND Iron deficiency without anemia has been shown to reduce both muscle-tissue oxidative capacity and endurance in animals . However , the consequences of iron deficiency in humans remain unclear . OBJECTIVE We investigated the effects of iron supplementation on adaptation to aerobic training among marginally iron-depleted women . We hypothesized that iron supplementation for 6 wk would significantly improve iron status and maximal oxygen uptake ( VO(2)max ) after 4 wk of concurrent aerobic training . DESIGN Forty-one untrained , iron-depleted , nonanemic women were r and omly assigned to receive either 50 mg FeSO(4 ) or a placebo twice daily for 6 wk in a double-blind trial . All subjects trained on cycle ergometers 5 d/wk for 4 wk , beginning on week 3 of the study . RESULTS Six weeks of iron supplementation significantly improved serum ferritin and serum transferrin receptor ( sTfR ) concentrations and transferrin saturation without affecting hemoglobin concentrations or hematocrit . Average VO(2)max and maximal respiratory exchange ratio improved in both the placebo and iron groups after training ; however , the iron group experienced significantly greater improvements in VO(2)max . Both iron-status and fitness outcomes were analyzed after stratifying by baseline sTfR concentration ( > and < or = 8.0 mg/L ) , which showed that the previously observed treatment effects were due to iron-status and fitness improvements among subjects with poor baseline iron status . CONCLUSIONS Our findings strongly suggest that iron deficiency without anemia but with elevated sTfR status impairs aerobic adaptation among previously untrained women and that this can be corrected with iron supplementation BACKGROUND We previously showed that iron supplementation significantly improves iron status and maximal work capacity in previously untrained , marginally iron-deficient women with a baseline serum transferrin receptor concentration > 8.0 mg/L. However , the effect of transferrin receptor status on adaptation in endurance capacity after aerobic training in these subjects has not been fully explored . OBJECTIVE Our objective was to examine the effect of baseline serum transferrin receptor status on adaptations in endurance capacity . DESIGN Forty-one untrained , iron-depleted , nonanemic women were r and omly assigned to receive either 100 mg FeSO(4 ) or a placebo for 6 wk in a double-blind trial . All subjects trained on cycle ergometers 5 d/wk for the last 4 wk of the study . Endurance capacity was assessed at baseline and after treatment by using a 15-km time trial conducted on a cycle ergometer . RESULTS Significant treatment effects were observed for time to complete the 15-km time trial , work rate , and percentage of maximal oxygen uptake in subjects with a baseline serum transferrin receptor concentration > 8.0 mg/L. No significant treatment effects were observed in subjects with a normal baseline transferrin receptor concentration . CONCLUSIONS Our findings suggest that , in the presence of overt tissue iron deficiency , iron deficiency without anemia impairs adaptation in endurance capacity after aerobic training in previously untrained women . This impairment can be corrected with iron supplementation Eighty iron-deficient , nonpregnant female workers were r and omly assigned to ferrous sulphate ( 60 or 120 mg Fe/d ) or placebo treatment for 12 wk . Energy expenditure was estimated during 3 d by heart rate ( HR ) recording . Production efficiency ( PE ) was calculated as the ratio of productivity to energy expenditure . In the iron-treated group mean hemoglobin ( Hb ) increased from 114 to 127 g/L ( P < 0.001 ) , mean serum ferritin increased from 9.7 to 30.0 micrograms/L ( P < 0.001 ) , and mean free erythrocyte protoporphyrin decreased from 1.01 to 0.49 mumol/L ( P < 0.001 ) . Mean HR at work decreased from 95.5 to 91.1 beats/min ( P < 0.001 ) , which was inversely correlated with the change in Hb ( r = -0.60 , P < 0.001 ) . PE increased significantly in the iron-treated group ( P < 0.001 ) and its change paralleled the change in Hb ( r = 0.58 , P < 0.001 ) . The results show that iron supplementation enabled these women to do the same work at a lower energy cost Studies in laboratory animals found that iron deficiency without anemia decreased oxidative capacity and increased reliance on carbohydrate as the substrate for energy , thereby causing impaired endurance . The purpose of this cross-sectional study was to investigate the relation between iron deficiency without anemia and physical performance in healthy active women aged 19 - 36 y. Iron-status assessment included determination of hemoglobin , hematocrit , transferrin saturation , and serum ferritin values . Dietary iron intake was assessed by frequency question naires and physical activity level was estimated by frequency question naires and 2-wk records . Fifteen women with normal iron status and 15 women with iron depletion ( serum ferritin < 12 micrograms/L ) were chosen r and omly from a group of 69 nonanemic women and given physical-performance tests , including determinations of maximum oxygen consumption ( VO2max ) , ventilatory threshold , and delta-efficiency . There were no significant differences between the two groups in body size , body composition , physical activity level , dietary iron intake , delta-efficiency , or ventilatory threshold . Compared with the iron-depleted group , the iron-sufficient group had significantly higher hemoglobin , transferrin saturation , and serum ferritin values and a significantly greater tendency to use iron supplements . When physical activity level and fat-free mass were controlled for , the iron-depleted group had a significantly lower VO2max . The difference in VO2max was significantly associated with serum ferritin concentration ; hemoglobin value was not a significant confounder . Therefore , reduction of VO2max in nonanemic women with iron depletion was likely caused by factors related to reduced body iron storage but was unrelated to decreased oxygen-transport capacity of the blood BACKGROUND Tissue iron depletion may negatively affect endurance performance and muscle fatigability . OBJECTIVE We investigated tissue-level iron depletion and progressive fatigue of the quadriceps during dynamic knee-extension exercise in young women . DESIGN Twenty iron-depleted ( serum ferritin < 20 micro g/L ) , nonanemic ( hemoglobin > 110 g/L ) women ( macro x + /- SEM age : 29.1 + /- 1.2 y ) received iron ( iron group ) or placebo ( placebo group ) for 6 wk in a r and omized , double-blind trial ( n = 10 per group ) . A protocol integrating 2 - 3-s maximal voluntary static contractions ( MVCs ) with dynamic knee extensions was used to assess fatigue . RESULTS No significant differences between the groups in baseline iron status , MVC at rest , or MVC at the end of the protocol were observed . After treatment , serum iron and transferrin saturation increased significantly in the iron group ( P = 0.02 and P = 0.03 , respectively ) . Serum transferrin receptor concentrations increased significantly in the placebo group ( P < 0.01 ) but not in the iron group . After treatment , the rate of decrease in MVC was attenuated in the iron group but not in the placebo group ( P = 0.01 ) . In the iron group , MVC at the sixth minute of the fatigue protocol and MVC at the end of the protocol were approximately 15 % ( P = 0.04 ) and approximately 27 % higher ( P < 0.01 ) , respectively , after treatment . These improvements were not related to changes in iron-status indexes or tissue iron stores , although power was low ( < 0.50 ) to detect these relations . CONCLUSIONS Iron supplementation was associated with a significant improvement in muscle fatigability . Interpretation regarding the direct role of tissue iron status is limited by the study 's low power to detect relations between tissue iron improvement and decreased muscle fatigue Forty-seven previously sedentary women participating in a 12-wk moderate aerobic-exercise program were r and omly assigned to one of four dietary groups : 50-mg/d iron supplement and a low food-iron diet ( 50 FE + EX ) , 10-mg/d iron supplement and a low food-iron diet ( 10 FE + EX ) , placebo and unrestricted diet ( P + EX ) , and meat supplement and high food-iron diet ( M + EX ) . A sedentary control group ( n = 13 ) received no dietary interventions . Hematocrit , total iron-binding capacity , and hemoglobin , serum iron , serum ferritin , and serum albumin concentrations were measured every 4 wk . Hemoglobin values decreased at the end of 4 wk in all exercising groups compared with the control group . Iron status in the 50 FE + EX and M + EX groups improved after week 4 as indicated by an increase in serum ferritin , serum iron , and hemoglobin concentrations , and a decline in total iron-binding capacity . Thus , short-term , moderate aerobic exercise result ed in compromised iron status that was offset to varying degrees by ingesting iron or meat supplements . However , meat supplements were more effective in protecting hemoglobin and ferritin status than were iron supplements Background Iron deficiency without anemia is related to adverse symptoms that can be relieved by supplementation . Since a blood donation can induce such an iron deficiency , we investigated the clinical impact of iron treatment after a blood donation . Methods One week after donation , we r and omly assigned 154 female donors with iron deficiency without anemia , aged below 50 years , to a four-week oral treatment of ferrous sulfate versus a placebo . The main outcome was the change in the level of fatigue before and after the intervention . Aerobic capacity , mood disorder , quality of life , compliance and adverse events were also evaluated . Hemoglobin and ferritin were used as biological markers . Results The effect of the treatment from baseline to four weeks of iron treatment was an increase in hemoglobin and ferritin levels to 5.2 g/L ( P < 0.01 ) and 14.8 ng/mL ( P < 0.01 ) , respectively . No significant clinical effect was observed for fatigue ( -0.15 points , 95 % confidence interval -0.9 points to 0.6 points , P = 0.697 ) or for other outcomes . Compliance and interruption for side effects was similar in both groups . Additionally , blood donation did not induce overt symptoms of fatigue in spite of the significant biological changes it produces . Conclusions These data are valuable as they enable us to conclude that donors with iron deficiency without anemia after a blood donation would not clinical ly benefit from iron supplementation . Trial Registration Clinical Trials.gov : PURPOSE The purpose of this study was to find out whether iron repletion leads to an increase in red blood cell volume ( RBV ) and performance capacity in iron-deficient nonanemic athletes . METHODS 40 young elite athletes ( 13 - 25 yr ) with low serum ferritin ( < 20 microg . L-1 ) and normal hemoglobin ( males > 13.5 g.dL-1 , females > 11.7 g.dL-1 ) were r and omly assigned to 12-wk treatment with either twice a day ferrous iron ( equivalent to 2 x 100 mg elemental iron ) or with placebo using a double blind method . Before and after treatment , hematological measures and parameters of iron status were determined in venous blood . RBV , blood volume ( BV ) , and plasma volume ( PV ) were measured by CO rebreathing . For determination of the aerobic and anaerobic capacity ( maximal accumulated oxygen deficit , MAOD ) , the athletes performed an incremental as well as a highly intensive treadmill test . RESULTS After 12 wk , ferritin levels were within the normal range in the iron-treated group ( IG ) with a significant ( P < 0.001 ) mean increase by 20 microg . L-1 opposed to a slight nonsignificant decrease in the placebo group ( PG ) . RBV did not change significantly in either group nor did any of the hematological measures . However , only in IG there were significant increases in VO2max and in O2 consumption in the MAOD test . MAOD and maximal capillary lactate concentration remained unchanged in both treatment groups . CONCLUSIONS The results indicate that in young elite athletes with low serum ferritin and normal hemoglobin concentration iron supplementation leads to an increase in maximal aerobic performance capacity without an augmentation of RBV In 781 female college students , there were 41 cases of iron deficiency anemia , 209 of latent iron deficiency , 3 of other anemias , and 528 normal cases . Fifty-four volunteers recruited from the iron deficiency anemia and severe latent iron deficiency groups were r and omly divided into 4 study groups . Groups I and III received 500 mg of vitamin C daily , and groups II and IV received ferric ammonium citrate ( FeAC ; equivalent to 6 mg iron ) in addition to vitamin C for 9 weeks . Groups I and II were loaded by aerobic exercise at 50 % VO2 max . Significant differences between groups were noted in serum ferritin ( SF ) in III/IV , hematocrit ( Ht ) in II/III and III/IV , and reticulocytes ( RET ) in I/II , I/IV , and III/IV . Hemoglobin ( Hb ) and other iron-related blood indices tended to normalize in groups II and IV when compared with the pre-values . VO2 max was elevated in groups I and II regardless of iron treatment , but was augmented more in group II than group The purpose of this investigation was to examine the effects of oral iron supplementation on endurance performance in initially iron-depleted , nonanemic female distance runners . Eighteen iron-depleted ( serum ferritin less than 20 ng.ml-1 , hemoglobin greater than or equal to 12 g.dl-1 ) women ( 22 - 39 yr ) performed a VO2max test and an endurance run to exhaustion . Subjects were pair-matched on the basis of endurance time and then r and omly assigned to an iron supplement or a placebo group . Following supplementation , the iron group had a significantly higher ( P = 0.03 ) mean serum ferritin concentration ( 23.4 vs 15.7 ng.ml-1 ) and lower ( P = 0.04 ) mean total iron-binding capacity than the placebo group . Both groups increased their time to exhaustion ( 25.5 % and 22.2 % for the iron and placebo groups , respectively ) but were not significantly different ( P = 0.72 ) from each other . There were also no differences ( P greater than 0.05 ) between the groups with respect to lactate concentrations and physiological measures taken during the two exercise tests . The results of this study suggest that 8 wk of oral iron supplementation improves iron status in iron-depleted female distance runners , but does not enhance endurance capacity We studied the effect of 2 weeks of iron therapy on exercise performance and exercise-induced lactate production in trained women athletes : six control subjects with normal parameters of iron status and nine with mild iron-deficiency anemia defined by low Fe/TIBC , ferritin , and minimally decreased Hgb values .  Iron therapy improved the abnormal measures of iron status and low Hgb in the second group to normal . Exercise performance in a progressive work-exercise protocol on a bicycle ergometer to exhaustion was unchanged after iron therapy in both groups ; however , blood lactate levels at maximum exercise in the iron-deficient group decreased significantly from 10.3 + /- 0.6 mmol/L before therapy to 8.42 + /- 0.7 after therapy ( p less than 0.03 ) . The control subjects did not significantly alter lactate levels after maximal exercise on iron compared to placebo : 8.3 + /- 0.8 mmol/L vs. 8.5 + /- 0.7 . Although there was not a significant difference in maximum exercise performance after iron therapy , these data support animal experiments implying that iron may play a role in oxidative metabolism and that minimal decreases in Hgb may impair arterial oxygen content enough to affect aerobic metabolism . In addition , these findings may have important implication s for competitive women athletes in whom mild iron deficiency may go unnoticed Objective : To determine the effect of iron supplementation on iron status and endurance capacity . Design : R and omized , double-blind iron supplementation . Setting : University of Missouri-Columbia and surrounding community . Subjects : Twenty iron-deficient ( serum ferritin , sFer<16 μg/l ; serum transferrin receptor , sTfR>8.0 mg/l ; or sTfR/log sFer index > 4.5 ) , nonanemic ( hemoglobin , Hb>120 g/l , women ; > 130 g/l , men ) men and women ( 18–41 years ) were recruited via fliers and newspaper advertisements ; 20 of 31 eligible subjects participated . Interventions : A 30 mg measure of elemental iron as ferrous sulfate or placebo daily for 6 weeks . Results : Dietary iron intake and physical activity did not differ between groups before or after supplementation . Iron supplementation significantly increased sFer compared to placebo ( P=0.01 ) , but did not affect Hb or hematocrit . Iron supplementation prevented the decline in ventilatory threshold ( VT ) observed in the placebo group from pre- to post-supplementation ( P=0.01 ) ; this effect was greater in individuals with lower sFer before intervention ( P<0.05 ) . Changes in sFer from pre- to post-treatment were positively correlated with changes in VT ( P=0.03 ) , independent of supplementation . The iron group significantly increased gross energetic efficiency during the submaximal test ( P=0.04 ) . Changes in sFer were negatively correlated with changes in average respiratory exchange ratio during the submaximal test ( P<0.05 ) . Conclusions : Iron supplementation significantly improves iron status and endurance capacity in iron-deficient , nonanemic trained male and female subjects . Sponsorship : Missouri University Alumni Association , by the Elizabeth Hegarty Foundation and by the Department of Nutritional Sciences Summary Serum iron deficiency has a high incidence in female athletes . We investigated the effects of a daily oral iron supplement , ( 160 mg ) administered during an intensive 7-week physical training programme , on body iron status , and the maximal aerobic capacity ( VO2max ) of 13 women ( group A ) compared to 15 who took a placebo ( group B ) . The subjects were 19 years old . Blood sample s were obtained before training began and on days 1 , 7 , 21 and 42 of training . They were analysed for packed cell volume ( PVC ) and for haemoglobin ( Hb ) , 2,3-diphosphoglycerate ( 2,3-DPG ) , haptoglobin , iron and ferritin concentrations . TheVO2max was measured on days 0 , 21 and 42 of training . Following 21 days of training Hb , PCV and ferritin were significantly higher ( P⩽0.01 ) in group A compared to group B. Over the training period Hb rose by 9.3 % and 2.4 % in groups A and B , respectively . At the end of training 66 % of group B exhibited ferritin concentrations below 10 ng·ml−1 , while none of group A had such low values . MeanVO2max of group A had increased by 7.5 % following 21 days of training ( P⩽0.01 ) and by 15.3 % after 42 days . No appreciable increase inVO2max had occurred in group B by day 21 ( significantly lower thanVO2max of group A;P⩽0.05 ) , however by day 42 it had increased by 14.3 % ( P⩽0.05 ) . In both groups 2,3-DPG·g Hb−1 had increased significantly ( P⩽0.005 ) by day 7 ( 22 % ) and remained at that level for an additional 35 days . We concluded that a daily oral iron supplement given to young women during intensive training improved several haematological variables and their body iron status . This improvement was associated with an increasedVO2max only during the early stages of their training ( day 21 ) compared with the placebo group Serum transferrin receptor ( sTfR ) concentration has been recognized recently as a reliable indicator of functional iron deficiency , but its response to iron supplementation has not been investigated in marginally iron-deficient women . In this r and omized , double-blinded trial , 37 female subjects aged 19 - 35 y with iron depletion without anemia ( hemoglobin > 120 g/L and serum ferritin < 16 microg/L ) received an iron supplement or placebo for 8 wk . Iron status was measured before treatment , after 4 wk of treatment , and posttreatment ( ie , after 8 wk of treatment ) . Iron supplementation of these iron-depleted , nonanemic women result ed in a progressive and significant decrease in sTfR and a significant increase in serum ferritin , and prevented a fall in hemoglobin . The responsiveness of sTfR to iron treatment indicated that sTfR is a sensitive indicator of marginal iron deficiency in iron-depleted , nonanemic women , even when their body iron stores were being replenished To determine the effects of an 8-wk dietary iron supplementation ( 100 mg.d-1 ) on low plasma ferritin concentration ( < 20 ng.ml-1 ) and endurance , 20 active women ( 19 - 35 yr ) were studied while performing a VO2max test and an endurance test ( 80 % VO2max ) on a cycle ergometer . Subjects were r and omly placed in an iron supplement ( IG ) or a placebo group ( PG ) using a double-blind method . After treatment in the IG , ferritin levels were higher ( 22.5 + /- 3.4 vs 14.3 + /- 2.2 ng.ml-1 ; P < 0.05 ) , Hb increased ( 12.8 + /- 0.4 to 14.1 + /- 0.2 g.dl-1 ; P < 0.05 ) , and TIBC decreased ( 366.2 + /- 24.8 to 293.8 + /- 14.0 micrograms.dl-1 ; P < 0.05 ) . Also after treatment the IG 's VO2max was significantly greater ( P < 0.05 ) than the PG value and their postendurance blood lactate decreased ( 5.03 + /- 0.44 to 3.85 + /- 0.6 mM.l-1 ; P < 0.05 ) . Endurance time to exhaustion increased 38 % ( 37.28 + /- 5.03 to 51.4 + /- 7.45 min ) following iron treatment ; however , this change was not statistically significant . The results suggest that this level of iron supplementation can reverse mild anemia , increase VO2max , and reduce blood lactate concentration after submaximal exercise The purpose of this study was to determine the effects of two weeks of high dosage iron supplementation on various blood iron indices and metabolic parameters in non-anemic , iron-depleted competitive female cross-country runners . The subjects were highly trained members of the Colorado State University cross-country team and were completing 40 to 50 miles of training weekly . A pretest , post-test single-blind crossover design was employed . Upon collection of baseline exercise blood and metabolic data , five subjects were r and omly assigned to iron supplementation ( 650 mg ferrous sulfate ; 130 mg elemental iron ) and five subjects to placebo treatment . At two weeks the treatments were reversed . Exercise blood and metabolic data were collected at two-week intervals . Dietary iron intake was assessed using a three-day dietary survey . Dietary analysis revealed deficiencies in vitamin B-6 , iron , magnesium , and zinc according to USRDA st and ards . Baseline blood sample s revealed no deficiencies in iron storage or transport proteins . Two weeks of iron supplementation result ed in no significant increases in blood iron indices . Metabolic parameters related to running performance were also unchanged after iron supplementation . High dosage , short-term iron supplementation appears to have no effect on blood or metabolic parameters in iron-depleted but non-anemic female cross-country runners Iron supplementation strategies in the developing world remain controversial because of fears of exacerbating prevalent infectious diseases . Underst and ing the conditions in which iron will be absorbed and incorporated into erythrocytes is therefore important . We studied Gambian children with either postmalarial or nonmalarial anemia , who were given oral iron supplements daily for 30 days . Supplements administered on days 1 and 15 contained the stable iron isotopes 57Fe and 58Fe , respectively , and erythrocyte incorporation was measured in blood sample s drawn 14 days later . We investigated how the iron-regulatory hormone hepcidin and other inflammatory/iron-related indices , all measured on the day of isotope administration , correlated with erythrocyte iron incorporation . In univariate analyses , hepcidin , ferritin , C-reactive protein , and soluble transferrin receptor ( sTfR ) strongly predicted incorporation of 57Fe given on day 1 , while hepcidin , ferritin , and sTfR/log ferritin correlated with 58Fe incorporation . In a final multivariate model , the most consistent predictor of erythrocyte isotope incorporation was hepcidin . We conclude that under conditions of competing signals ( anemia , iron deficiency , and infection ) , hepcidin powerfully controls use of dietary iron . We suggest that low-cost point-of-care hepcidin assays would aid iron supplementation programs in the developing world Low serum ferritin concentrations are commonly found in female athletes . By study ing the effects of an 8-week iron or placebo supplementation in 31 female athletes ( aged 17 - 31 years ) , with an initial serum ferritin concentration less than or equal to 25 micrograms/l and blood hemoglobin 120 g/l , we investigated whether low serum ferritin values hinder aerobic performance . Serum ferritin concentration increased from 14 ( 25th and 75th percentile : 11 , 21 ) to 26 ( 18 , 36 ) micrograms/l in the iron-supplemented group , but remained at a low 11 ( 9 , 17 ) micrograms/l in the placebo group ( group difference after supplementation : p = 0.001 ) . Before supplementation , blood hemoglobin concentration was not different in the two groups . After supplementation , however , the concentration in the iron group was 139 ( 135 , 144 ) g/l and 128 ( 126 , 134 ) g/l in the placebo group ( group difference : p = 0.001 ) . Iron supplementation did not affect blood lactate concentration or VO2max during an incremental ergometer test . Hence , aerobic performance was not impaired in nonanemic female athletes with serum ferritin 25 micrograms/l Iron-deficiency anemia impairs exercise capacity , but whether nonanemic iron depletion decreases endurance performance is unclear . In 14 iron-deficient ( serum ferritin level , less than 20 micrograms/L [ less than 20 ng/L])nonanemic runners , hematologic and treadmill running values were followed up during a competitive season . Following a four-week control period , runners were treated for one month in a double-blind protocol with ferrous sulfate ( 975 mg/d ) or placebo . During treatment , the mean ferritin level rose from 8.7 to 26.6 micrograms/L ( 8.7 to 26.6 ng/mL ) in those patients taking iron and fell from 10.6 to 8.6 micrograms/L ( 10.7 to 8.6 ng/mL ) in the placebo group . Treadmill endurance times improved significantly in the iron-treated runners compared with controls . Endurance time declined in all seven controls ( range , 0.07 to 1.30 minutes ) , while six of seven iron-treated subjects improved their performance ( range , 0.03 to 1.92 minutes ) . No significant differences in maximal or submaximal oxygen consumption , ventilation , or heart rate were observed between the groups except for a 4 % increase in maximum oxygen consumption during placebo treatment . These data indicate that nonanemic iron deficiency impairs exercise performance but does not influence gas exchange or cardiac measures BACKGROUND Decrements in iron status have been reported in female soldiers during military training . Diminished iron status adversely affects physical and cognitive performance . OBJECTIVE We wanted to determine whether iron supplementation could prevent decrements in iron status and improve measures of physical performance and cognitive status in female soldiers during basic combat training ( BCT ) . DESIGN In this 8-wk r and omized , double-blind , placebo-controlled trial , soldier volunteers ( n = 219 ) were provided with capsules containing either 100 mg ferrous sulfate or a placebo . Iron status indicator assays were performed pre- and post-BCT . Two-mile running time was assessed post-BCT ; mood was assessed by using the Profile of Mood States question naire pre- and post-BCT . RESULTS The BCT course affected iron status : red blood cell distribution width and soluble transferrin receptor were elevated ( P < 0.05 ) , and serum ferritin was lowered ( P < 0.05 ) post-BCT . Iron supplementation attenuated the decrement in iron status ; group-by-time interactions ( P < 0.01 ) were observed for serum ferritin and soluble transferrin receptor . Iron supplementation result ed 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 . CONCLUSIONS Iron status is affected by BCT , and iron supplementation attenuates the decrement in indicators of iron status in female soldiers . Furthermore , iron supplementation may prove to be beneficial for mood and physical performance during the training period . Future efforts should identify and treat female soldiers or athletes who begin training regimens with iron deficiency or iron deficiency anemia There was no significant change in the maximal oxygen uptake for either the experimental or the control group from the pre-test to the post-test . Five blood chemistry measures were unable to predict the post-maximal oxygen uptake scores using the procedure of stepwise regression . An examination of the blood chemistry profiles indicated that sports anemia did not occur . The factorial breakdown was unable to produce any significant insight into the changes in hemoglobin concentration and oxygen consumption .  Heme-iron supplementation was unable to override the regulatory system of the body and allow the hemoglobin level to become elevated In order to examine the effects of mild iron deficiency on physical work capacity , 40 prelatent iron-deficient female endurance runners were studied before and after 8 wk of supplementation with either oral iron ( 320 mg ferrous sulfate ) or a matching placebo . Subjects underwent the following physical work capacity tests : the Wingate cycle ergometer test , the anaerobic speed test , the ventilatory threshold , VO2max , and maximal treadmill velocity during the VO2max test . Muscle biopsy sample s pre- and post-treatment were obtained from 17 of the subjects , and these were assayed for citrate synthase and cytoplasmic alpha-glycerophosphate dehydrogenase activity . Subjects were r and omly assigned to one of the treatment groups , and a double-blind method of administration of the supplements was used . The differences in improvement scores between the two groups on the work capacity and enzyme activity variables were statistically nonsignificant ( P greater than 0.05 ) . Serum ferritin values rose from a mean of 12.4 + /- 4.5 to 37.7 + /- 19.7 ng.ml-1 for the experimental group and from 12.2 + /- 4.3 to 17.2 + /- 8.9 ng.ml-1 for the controls ( P = 0.0025 ) , whereas hemoglobin levels remained fairly constant for both groups ( P = 0.6 ) . Eight weeks of iron supplementation to prelatent/latent iron-deficient , physically active females did not significantly enhance work capacity . Within the limitations of this study , the presence of a serum ferritin below 20 ng.ml-1 does not pose a significant h and icap to physical work capacity The effects of energy supplementation ( group I received 200 kcal/day and group II received 1000/kcal day ) were examined on road workers in Kenya .  Anthropometric , dietary , worker productivity , clinical hematology , and parasitology data were collected from 224 workers of both sexes or , sub sample s of these workers at base-line , midpoint , and final measurement periods . Sixty-seven percent of the work force was less than 85 % of weight for height . Females tended to be better nourished than males . Multiple regression analysis showed that increases in arm circumference and Hb levels were associated with significant productivity gains of about 4 % . At the midpoint , group II males gained 1.10 kg ( p less than 0.0003 ) while group I males showed no change . Weight loss during the latter part of the study result ed in no significant final weight change for males . " Successful " supplementation was weakly associated with a productivity increase for group II workers of 12.5 % ( p less than 0.10 ) The impact of long-term ( 6-month ) moderate exercise on the iron status of previously sedentary women was determined by r and omly assigning 62 college-age women into one of the following four groups : 1 ) 50 mg.d-1 iron supplement , low iron diet ( N = 16 ) ; 2 ) Placebo , free choice diet ( N = 13 ) ; 3 ) Meat supplement to achieve 15 mg.d-1 iron intake ( N = 13 ) ; and 4 ) Control , free choice diet ( N = 20 ) . All groups except the Control group exercised 3 d.wk-1 at 60%-75 % of their heart rate reserve . VO2max was measured at baseline and week 24 . Blood was sample d at baseline and every 4 wk thereafter for 24 wk to measure iron status and to eluci date the causes for alterations in iron status . Subjects had depleted iron stores throughout the study as indicated by their serum ferritin levels ( < 15 ng.ml-1 ) . Serum iron , total iron binding capacity and transferrin saturation were not compromised with exercise . Mean hemoglobin level in the Placebo/Ex group was significantly ( P < 0.05 ) lower than the 50 Fe/Ex and the Meat/Ex groups by week 24 . However , changes in serum albumin , haptoglobin , and erythropoietin data from the study can not explain these changes
target: Daily iron supplementation significantly improves maximal and submaximal exercise performance in WRA , providing a rationale to prevent and treat iron deficiency in this group .
background: Animal and human observational studies suggest that iron deficiency impairs physical exercise performance , but findings from r and omized trials on the effects of iron are equivocal .
  Iron deficiency and anemia are especially common in women of reproductive age ( WRA ) .
  Clear evidence of benefit from iron supplementation would inform clinical and public health guidelines .
  Therefore , we performed a systematic review and meta- analysis to determine the effect of iron supplementation compared with control on exercise performance in WRA .