Department of Epidemiology, Boston University School of Public Health, Boston, MA.
Department of Clinical Epidemiology, Aarhus University Hospital, Denmark.
J Nutr. 2019 Sep 1;149(9):1585-1595. doi: 10.1093/jn/nxz094.
Infertility is an important public health problem with few known modifiable risk factors. Dietary factors including folic acid have been associated with improved fertility, but the association between iron and fertility is understudied. One study among US nurses found a 40% lower risk of ovulatory infertility with higher intake of nonheme iron and iron supplements.
The aim of this study was to determine the extent to which iron intake from diet and supplements reported on structured questionnaires is associated with fecundability.
We conducted parallel analyses that used data from 2 prospective cohort studies of pregnancy planners from Denmark (Snart Foraeldre; n = 1693) and North America (PRESTO; n = 2969) during 2013-2018. Follow-up comprised menstrual cycles at risk until pregnancy or censoring for fertility treatment, stopped trying to conceive, withdrawal, loss to follow-up, or 12 cycles of attempt. We used proportional probabilities regression models to estimate fecundability ratios (FRs) and 95% CIs, adjusting for confounders.
We found little association between dietary heme iron intake and fecundability in either cohort. The FR for nonheme iron intake (≥11 mg/d compared with <9 mg/day) was 1.11 for Snart Foraeldre participants (95% CI: 0.92, 1.34) and 1.01 for PRESTO participants (95% CI: 0.89, 1.14). The FR for iron-containing supplements was 1.01 in Snart Foraeldre (95% CI: 0.90, 1.13) and 1.19 in PRESTO (95% CI: 1.03, 1.38). In PRESTO, but not Snart Foraeldre, stronger positive associations were found for nonheme iron intake and iron supplement use among women with heavy menses or short menstrual cycles.
Overall, dietary intake of iron was not consistently associated with fecundability, although there was some evidence for a positive association among women with risk factors for iron deficiency. We also found a small positive association between supplemental iron intake and fecundability among North American, but not Danish, pregnancy planners.
不孕是一个重要的公共卫生问题，其已知的可改变的危险因素很少。包括叶酸在内的饮食因素与提高生育能力有关，但铁与生育能力的关系研究较少。一项针对美国护士的研究发现，较高的非血红素铁和铁补充剂摄入量与排卵性不孕的风险降低 40%有关。
本研究旨在确定基于结构问卷报告的饮食和补充剂中铁的摄入量与生育能力之间的关联程度。
我们进行了平行分析，这些分析使用了 2013-2018 年丹麦（Snart Foraeldre；n=1693）和北美（PRESTO；n=2969）妊娠计划者的 2 项前瞻性队列研究的数据。随访包括妊娠或因生育治疗、停止尝试受孕、退出、失访或尝试 12 个周期而终止的风险月经周期。我们使用比例概率回归模型来估计生育能力比值（FR）和 95%置信区间（CI），并对混杂因素进行调整。
我们在两个队列中都发现饮食血红素铁摄入量与生育能力之间几乎没有关联。Snart Foraeldre 参与者的非血红素铁摄入量（≥11 mg/d 与 <9 mg/d）的 FR 为 1.11（95%CI：0.92，1.34），PRESTO 参与者的 FR 为 1.01（95%CI：0.89，1.14）。含铁补充剂的 FR 在 Snart Foraeldre 中为 1.01（95%CI：0.90，1.13），在 PRESTO 中为 1.19（95%CI：1.03，1.38）。在 PRESTO 中，但在 Snart Foraeldre 中没有，月经过多或月经周期较短的女性中，非血红素铁摄入和铁补充剂使用与生育能力呈更强的正相关。
总的来说，饮食中铁的摄入量与生育能力没有一致的关联，但在缺铁风险因素的女性中，有一些证据表明存在正相关。我们还发现，北美，而不是丹麦，妊娠计划者中补充铁摄入与生育能力之间存在小的正相关。
