Heseker Helmut B, Mason Joel B, Selhub Jacob, Rosenberg Irwin H, Jacques Paul F
Department of Nutrition and Consumer Education, University Paderborn, Warburger Strasse 100, D-33098 Paderborn, Germany.
Br J Nutr. 2009 Jul;102(2):173-80. doi: 10.1017/S0007114508149200. Epub 2008 Dec 16.
Some countries have introduced mandatory folic acid fortification, whereas others support periconceptional supplementation of women in childbearing age. Several European countries are considering whether to adopt a fortification policy. Projections of the possible beneficial effects of increased folic acid intake assume that the measure will result in a considerable reduction in neural-tube defects (NTD) in the target population. Therefore, the objective of the present study is to evaluate the beneficial effects of different levels of folic acid administration on the prevalence of NTD. Countries with mandatory fortification achieved a significant increase in folate intake and a significant decline in the prevalence of NTD. This was also true for supplementation trials. However, the prevalence of NTD at birth declined to approximately five cases at birth per 10 000 births and seven to eight cases at birth or abortion per 10 000 births. This decline was independent of the amount of folic acid administered and apparently reveals a 'floor effect' for folic acid-preventable NTD. This clearly shows that not all cases of NTD are preventable by increasing the folate intake. The relative decline depends on the initial NTD rate. Countries with NTD prevalence close to the observed floor may have much smaller reductions in NTD rates with folic acid fortification. Additionally, potential adverse effects of fortification on other vulnerable population groups have to be seriously considered. Policy decisions concerning national mandatory fortification programmes must take into account realistically projected benefits as well as the evidence of risks to all vulnerable groups.
一些国家已推行强制性叶酸强化措施，而其他国家则支持对育龄妇女进行孕前补充。几个欧洲国家正在考虑是否采用强化政策。对增加叶酸摄入量可能产生的有益效果的预测假定，该措施将使目标人群中的神经管缺陷（NTD）大幅减少。因此，本研究的目的是评估不同水平叶酸给药对NTD患病率的有益效果。实行强制性强化措施的国家叶酸摄入量显著增加，NTD患病率显著下降。补充试验的情况也是如此。然而，出生时NTD的患病率降至每10000例出生约5例，每10000例出生或流产时为7至8例。这种下降与叶酸给药量无关，显然显示出叶酸可预防的NTD存在“底线效应”。这清楚地表明，并非所有NTD病例都可通过增加叶酸摄入量来预防。相对下降幅度取决于初始NTD率。NTD患病率接近观察到的底线的国家，通过叶酸强化使NTD率降低的幅度可能小得多。此外，必须认真考虑强化措施对其他弱势群体的潜在不利影响。关于国家强制性强化计划的政策决定必须切实考虑到预期的实际益处以及所有弱势群体面临风险的证据。
