Fujita Masako, Wander Katherine
Department of Anthropology, Michigan State University, Michigan.
Biomarker Laboratory for Anthropological Research, Michigan State University, Michigan.
Am J Phys Anthropol. 2017 Nov;164(3):586-597. doi: 10.1002/ajpa.23299. Epub 2017 Aug 19.
The optimal iron hypothesis posits a trade-off in iron nutrition-iron deficiency restricts iron available to infectious agents, protecting against severe infection, but also compromises immune defense-such that mild-to-moderate iron deficiency may be more adaptive than either iron-replete or severe deficiency in environments with high infectious disease load. This hypothesis has not been tested among adults.
A secondary analysis of data and specimens from 220 lactating mothers in northern Kenya was conducted. Elevated serum C-reactive protein (CRP > 2 or >5 mg/l) was utilized to identify prevalent subclinical infection/inflammation. Iron deficiency was identified with transferrin receptor in archived dried blood spots (TfR > 5.0 mg/l). The absence of iron deficiency or anemia (Hemoglobin < 12 g/l) defined the iron replete state. Iron-deficient erythropoiesis (IDE, mild-to-moderate iron deficiency) was defined as iron deficiency without anemia; iron deficiency anemia (IDA, severe iron deficiency) as iron deficiency with anemia; and noniron-deficiency anemia (NIDA) as anemia without iron deficiency.
The prevalence of elevated inflammation (subclinical infection) was lowest in IDE. In logistic regression, IDE was inversely associated with inflammation (for CRP > 2 mg/l: adjusted odds ratio, aOR = 0.30; p = 0.02; for CRP > 5 mg/l: aOR = 0.27; p = 0.10), compared to the iron replete state. The protective effect of IDE differed in the presence of vitamin A deficiency or underweight.
We interpret these patterns as tentative support for the optimal iron hypothesis in breastfeeding women in the infectious disease ecology of northern Kenya. Iron deficiency may interact in important ways with other forms of malnutrition that are known to affect immune protection.
最佳铁假说认为，铁营养存在一种权衡——缺铁会限制病原体可利用的铁，预防严重感染，但也会损害免疫防御——因此，在传染病负荷高的环境中，轻度至中度缺铁可能比铁充足或严重缺铁更具适应性。该假说尚未在成年人中得到验证。
对肯尼亚北部220名哺乳期母亲的数据和样本进行了二次分析。利用血清C反应蛋白升高（CRP>2或>5mg/l）来识别普遍存在的亚临床感染/炎症。通过存档干血斑中的转铁蛋白受体（TfR>5.0mg/l）来识别缺铁。铁充足状态定义为不存在缺铁或贫血（血红蛋白<12g/l）。缺铁性红细胞生成（IDE，轻度至中度缺铁）定义为缺铁但无贫血；缺铁性贫血（IDA，严重缺铁）定义为缺铁且伴有贫血；非缺铁性贫血（NIDA）定义为无缺铁的贫血。
IDE患者炎症（亚临床感染）升高的患病率最低。在逻辑回归分析中，与铁充足状态相比，IDE与炎症呈负相关（对于CRP>2mg/l：调整优势比，aOR = 0.30；p = 0.02；对于CRP>5mg/l：aOR = 0.27；p = 0.10）。在存在维生素A缺乏或体重不足的情况下，IDE的保护作用有所不同。
我们将这些模式解读为对肯尼亚北部传染病生态环境中哺乳期妇女最佳铁假说的初步支持。缺铁可能与已知影响免疫保护的其他形式的营养不良以重要方式相互作用。
