Garza D, Shrier I, Kohl H W, Ford P, Brown M, Matheson G O
Sports Medicine Division, Stanford University School of Medicine, California 94305, USA.
Clin J Sport Med. 1997 Jan;7(1):46-53. doi: 10.1097/00042752-199701000-00009.
It is common practice to measure serum ferritin levels in endurance athletes because of the belief that low iron stores may compromise performance. The direct relationship between endurance performance and iron deficiency anemia is well known, but there are theoretical reasons to believe that endurance performance may be adversely affected by low iron stores even in the absence of frank anemia. The purpose of this article is to provide a critical review of the scientific evidence relating low iron stores to endurance performance.
Medline was searched using MeSH for articles related to ferritin and endurance published since 1985. Additional references were reviewed from the bibliographies of the retrieved articles.
All clinical study designs were reviewed as well as relevant animal studies. Conclusions regarding endurance performance in humans were limited to data from clinical studies.
In reviewing the literature, the relative strengths of the study designs were examined carefully. Particular attention of the effectiveness of each study in isolating ferritin as the key independent variable. Dependent measures of endurance capacity were also evaluated.
Eight studies isolated serum ferritin as the experimental variable. Only one study reported a significant improvement in endurance performance (time to exhaustion) in subjects with low ferritin levels treated with oral iron, but this finding may have been magnified by an unexplained decrease in time to exhaustion in the control group. Iron dosages differed in the studies reviewed. Two additional studies that reported increases in performance parameters following increases in ferritin were confounded by concomitant increases in hemoglobin levels.
Iron supplementation can raise serum ferritin levels, but increases in ferritin concentration, unaccompanied by increases in hemoglobin concentration, have not been shown to increase endurance performance. Of concern to the clinician is that athletes with low ferritin levels but hemoglobin in the low-normal range may have iron deficiency anemia responsive to iron supplementation. Low ferritin with hemoglobin in the mid- to upper normal range is at best a relative indication for iron supplementation: low ferritin with hemoglobin in the low normal range is a stronger, yet still relative, indication for iron supplementation in athletes.
由于人们认为铁储备不足可能会影响耐力运动员的表现，所以测量其血清铁蛋白水平已成为一种常见做法。耐力表现与缺铁性贫血之间的直接关系是众所周知的，但有理论依据认为，即使在没有明显贫血的情况下，铁储备不足也可能对耐力表现产生不利影响。本文旨在对有关铁储备不足与耐力表现的科学证据进行批判性综述。
使用医学主题词（MeSH）在Medline数据库中检索自1985年以来发表的与铁蛋白和耐力相关的文章。还从检索到的文章的参考文献中查阅了其他参考文献。
对所有临床研究设计以及相关动物研究进行了综述。关于人类耐力表现的结论仅限于临床研究数据。
在回顾文献时，仔细检查了研究设计的相对优势。特别关注每项研究在将铁蛋白作为关键自变量进行分离方面的有效性。还评估了耐力能力的相关测量指标。
八项研究将血清铁蛋白作为实验变量。只有一项研究报告称，口服铁剂治疗的铁蛋白水平低的受试者的耐力表现（力竭时间）有显著改善，但这一发现可能因对照组力竭时间的 unexplained decrease 而被放大。在所综述的研究中，铁剂量各不相同。另外两项报告称铁蛋白增加后性能参数有所提高的研究，因血红蛋白水平同时升高而受到混淆。
补充铁剂可提高血清铁蛋白水平，但未显示铁蛋白浓度增加而血红蛋白浓度未增加会提高耐力表现。临床医生需要关注的是，铁蛋白水平低但血红蛋白处于低正常范围的运动员可能患有对铁补充剂有反应性的缺铁性贫血。铁蛋白低且血红蛋白处于中高正常范围充其量只是铁补充剂的相对指征：铁蛋白低且血红蛋白处于低正常范围是运动员补充铁剂的更强但仍然相对的指征。
