Obeid Rima, Koletzko Berthold, Pietrzik Klaus
Department of Clinical Chemistry and Laboratory Medicine, University Hospital of the Saarland, D-66421 Homburg, Germany.
Division of Metabolic and Nutritional Medicine, University of Munich Medical Centre, D-80337 Munich, Germany.
Clin Nutr. 2014 Apr;33(2):252-9. doi: 10.1016/j.clnu.2013.12.013. Epub 2014 Jan 14.
We evaluated the recommendation of the Austrian, German, and Swiss Societies for Nutrition of lowering dietary folate intake from 400 to 300 μg dietary folate equivalents/d. A dose-response relation exists between folate intake or plasma level and disease risk within the normal range. Improving folate status can prevent between 30% and 75% of neural tube defects. A prepregnancy plasma folate of >18.0 nmol/L (mean 26.1 nmol/L) is associated with low total homocysteine (tHcy) (<10.0 μmol/L) and optimal prevention of birth defects. Because the closure of the neural tube occurs in the first 8 weeks after conception, women with low prepregnancy folate intake cannot achieve maximal risk reduction. The Austrian, German, and Swiss Societies for Nutrition recommend that young women should additionally supplement with 400 μg folic acid at least 4 weeks before conception. This short time window is not sufficient to achieve optimal plasma folate and tHcy levels in the majority of women. Factors affecting the relation between folate intake and blood biomarkers are total folate intake, baseline plasma folate, time available for supplement use, dose and form (folic acid or methyl folate), genetic polymorphisms, physiological and lifestyle factors. Lowering the recommended dietary folate intake may have important public health consequences. Elderly people and young women are at risk for diseases related to folate shortage. Reducing birth defects through supplementation of folic acid remains a poor option, as <20% of young women (i.e., in Germany) supplement with the vitamin. Recommending adequate food folate intake is crucial for reaching the target protective plasma folate levels in the population.
我们评估了奥地利、德国和瑞士营养学会关于将膳食叶酸摄入量从400微克膳食叶酸当量/天降至300微克的建议。在正常范围内，叶酸摄入量或血浆水平与疾病风险之间存在剂量反应关系。改善叶酸状况可预防30%至75%的神经管缺陷。孕前血浆叶酸>18.0纳摩尔/升（平均26.1纳摩尔/升）与低总同型半胱氨酸（tHcy）（<10.0微摩尔/升）及最佳出生缺陷预防相关。由于神经管闭合发生在受孕后的前8周，孕前叶酸摄入量低的女性无法实现最大程度的风险降低。奥地利、德国和瑞士营养学会建议年轻女性在受孕前至少4周额外补充400微克叶酸。这个短时间窗口不足以使大多数女性达到最佳血浆叶酸和tHcy水平。影响叶酸摄入量与血液生物标志物之间关系的因素包括总叶酸摄入量、基线血浆叶酸、可用于补充剂使用的时间、剂量和形式（叶酸或甲基叶酸）、基因多态性、生理和生活方式因素。降低推荐的膳食叶酸摄入量可能会产生重要的公共卫生后果。老年人和年轻女性有患与叶酸缺乏相关疾病的风险。通过补充叶酸来减少出生缺陷仍然是一个不理想的选择，因为<20%的年轻女性（即德国的年轻女性）补充这种维生素。推荐足够的食物叶酸摄入量对于使人群达到目标保护性血浆叶酸水平至关重要。
