Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, GA, USA.
Institute of Nutrition and Food Technology, University of Chile, Santiago, Chile.
J Nutr. 2023 Jan;153(1):253-259. doi: 10.1016/j.tjnut.2022.10.002. Epub 2022 Dec 20.
Early onset of menarche is considered an important risk factor for a number of diseases in adulthood. Iron intake may be related to pubertal timing because of its role in childhood growth and reproductive function.
We investigated the relation between dietary iron intake and age at menarche in a prospective cohort of Chilean girls.
Overall, 602 Chilean girls were included in the Growth and Obesity Cohort Study, a longitudinal study that began in 2006 when the girls were 3-4 y old. Starting in 2013, diet was assessed every 6 mo through 24-h recall. The date of menarche was reported every 6 mo. Our analysis included 435 girls with prospective data on diet and age at menarche. We used a multivariable Cox proportional hazards regression model with restricted cubic splines to estimate HRs and 95% CIs for the association between cumulative mean iron intake and age at menarche.
Most girls (99.5%) attained menarche with a mean (standard deviation) age at menarche of 12.2 (0.9) y. The mean dietary iron intake was 13.5 (range: 4.0-30.6) mg/d. Only 3.7% of girls consumed below 8 mg/d, the RDA. After multivariable adjustment, cumulative mean iron intake had a nonlinear association with menarche (P-for-nonlinearity: 0.02). Iron intakes above the RDA, between 8 and 15 mg/d, were associated with progressively lower probability of earlier menarche. Above 15 mg/d, the HRs were imprecise but tended to approach the null as iron intake increased. This association was attenuated after adjusting for girls' BMI and height before menarche (P-for-nonlinearity: 0.11).
In Chilean girls, iron intake during late childhood, independent of body weight, was not an important determinant of menarche timing.
初潮提前被认为是成年后多种疾病的一个重要危险因素。铁的摄入可能与青春期开始时间有关，因为它在儿童生长和生殖功能中起着重要作用。
我们在智利女孩的前瞻性队列中研究了膳食铁摄入与初潮年龄的关系。
共有 602 名智利女孩参加了生长与肥胖队列研究，这是一项从 2006 年开始的纵向研究，当时女孩的年龄在 3-4 岁。从 2013 年开始，每 6 个月通过 24 小时回顾法评估饮食情况。每 6 个月报告一次初潮日期。我们的分析包括 435 名有前瞻性饮食数据和初潮年龄的女孩。我们使用多变量 Cox 比例风险回归模型和限制性立方样条来估计累积平均铁摄入量与初潮年龄之间的 HR 和 95%CI。
大多数女孩（99.5%）在 12.2（0.9）岁时初潮，平均初潮年龄。平均膳食铁摄入量为 13.5（范围：4.0-30.6）mg/d。只有 3.7%的女孩每天摄入铁量低于 8 毫克，低于 RDA。经过多变量调整后，累积平均铁摄入量与初潮呈非线性关系（P-非线性：0.02）。RDA 为 8-15mg/d 之间的铁摄入量与更早初潮的概率逐渐降低相关。超过 15 毫克/天，HR 不太精确，但随着铁摄入量的增加，趋于接近零。调整女孩初潮前的 BMI 和身高后，这种关联减弱（P-非线性：0.11）。
在智利女孩中，儿童晚期的铁摄入与体重无关，不是初潮时间的重要决定因素。
