Tucker K L, Mahnken B, Wilson P W, Jacques P, Selhub J
Jean Mayer US Department of Agriculture Human Nutrition Research Center on Aging at Tufts University, Boston, Mass 02111, USA.
JAMA. 1996 Dec 18;276(23):1879-85. doi: 10.1001/jama.1996.03540230029031.
To estimate the potential benefits and risks of food folic acid fortification for an elderly population. Benefits are expected through the improvement of folate and homocysteine status, but there is also a risk of masking or precipitating clinical manifestations related to vitamin B12 deficiency with increasing exposure to folic acid.
Cross-sectional analysis, with projected change at various levels of folic acid fortification.
Participants in the Framingham Heart Study original cohort.
A total of 747 subjects aged 67 to 96 years who both completed usable food frequency questionnaires and had blood concentrations of B vitamins and homocysteine measured.
Projected blood folate and homocysteine concentrations and combined high folate intake and low plasma vitamin B12 concentration.
Percentages of this elderly population with folate intake below 400 microg/d are projected to drop from 66% at baseline to 49% with 140 microg of folate per 100 g of cereal-grain product, to 32% with 280 microg, to 26% with 350 microg, and to 11% with 700 microg. Percentages with elevated homocysteine concentrations (>14 micromol/L) are projected to drop from 26% at baseline to 21% with 140 microg of folate per 100 g, to 17% with 280 microg, to 16% with 350 microg, and to 12% with 700 microg. Without fortification, the prevalence of combined high folate intake (>1000 microg/d) and low plasma vitamin B12 concentration (<185 pmol/L [<250 pg/mL]) was 0.1%. This is projected to increase to 0.4% with folate fortification levels of 140 to 350 microg/100 g and to 3.4% with 700 microg.
The evidence suggests that, at the level of 140 microg/100 g of cereal-grain product mandated by the Food and Drug Administration, the benefits of folate fortification, through projected decreases in homocysteine level and heart disease risk, greatly outweigh the expected risks. However, quantification of the actual risks associated with vitamin B12 deficiency remains elusive. Before higher levels of folic acid fortification are implemented, further research is needed to better understand the clinical course of various forms of vitamin B12 deficiency, to measure the potential effect of high folate intake on this course, and to identify cost-effective approaches to the identification and treatment of all forms of vitamin B12 deficiency.
评估食物叶酸强化对老年人群的潜在益处和风险。预计通过改善叶酸和同型半胱氨酸水平可带来益处，但随着叶酸摄入量增加，也存在掩盖或引发与维生素B12缺乏相关临床表现的风险。
横断面分析，并预测不同叶酸强化水平下的变化。
弗雷明汉心脏研究原始队列的参与者。
共有747名年龄在67至96岁之间的受试者，他们均完成了可用的食物频率问卷，并测量了血液中B族维生素和同型半胱氨酸的浓度。
预测的血液叶酸和同型半胱氨酸浓度，以及高叶酸摄入量与低血浆维生素B12浓度的组合情况。
预计该老年人群中叶酸摄入量低于400微克/天的比例将从基线时的66%降至每100克谷物产品中添加140微克叶酸时的49%，添加280微克时降至32%，添加350微克时降至26%，添加700微克时降至11%。同型半胱氨酸浓度升高（>14微摩尔/升）的比例预计将从基线时的26%降至每100克添加140微克叶酸时的21%，添加280微克时降至17%，添加350微克时降至16%，添加700微克时降至12%。在未强化的情况下，高叶酸摄入量（>1000微克/天）与低血浆维生素B12浓度（<185皮摩尔/升[<250皮克/毫升]）组合的患病率为0.1%。预计叶酸强化水平为140至350微克/100克时，这一患病率将增至0.4%，强化水平为700微克时将增至3.4%。
有证据表明，按照美国食品药品监督管理局规定的每100克谷物产品添加140微克叶酸的水平，叶酸强化通过预计降低同型半胱氨酸水平和心脏病风险带来的益处，大大超过预期风险。然而，与维生素B12缺乏相关的实际风险的量化仍不明确。在实施更高水平的叶酸强化之前，需要进一步研究以更好地了解各种形式维生素B12缺乏的临床病程，衡量高叶酸摄入量对该病程的潜在影响，并确定识别和治疗所有形式维生素B12缺乏的经济有效方法。
