van Velzen Agnes G, Sips Adrienne J A M, Schothorst Ronald C, Lambers Annette C, Meulenbelt Jan
National Poisons Information Centre, National Institute for Public Health and the Environment, P.O. Box 1, 3720 BA Bilthoven, The Netherlands.
Toxicol Lett. 2008 Oct 1;181(3):177-81. doi: 10.1016/j.toxlet.2008.07.019. Epub 2008 Aug 3.
High dietary nitrate intake may pose a risk to human health. Since up to 80-85% of dietary nitrate intake comes from vegetables, the aim of this study was to determine the absolute bioavailability of nitrate from three nitrate-rich vegetables. In an open, four-way cross-over, single dose study, 12 human subjects underwent the following treatments: (1) intravenous infusion of 500mg sodium nitrate, (2) oral administration of 300g cooked spinach, (3) oral administration of 300g raw lettuce, and (4) oral administration of 300g cooked beetroot. The wash-out period between treatments was at least 6 days. Plasma samples were analysed to assess the nitrate and nitrite concentrations, and pharmacokinetic parameters were calculated. The bioavailability of nitrate was 98+/-12% from cooked spinach, 114+/-14% from raw lettuce and 106+/-15% from cooked beetroot. There was no significant increase in plasma nitrite concentrations. This study shows that nitrate from vegetables, whether cooked or uncooked, is absorbed very effectively, resulting in an absolute nitrate bioavailability of around 100%. Thus, reducing the amount of nitrate in vegetables can be an effective measure to lower the systemic nitrate exposure of the general population. However, other aspects, such as the costs to produce vegetables with a low nitrate content and the possible beneficial effects of nitrate in vegetables, need to be considered when evaluating the usefulness of such a measure.
高膳食硝酸盐摄入量可能对人体健康构成风险。由于高达80 - 85%的膳食硝酸盐摄入量来自蔬菜，本研究的目的是确定三种富含硝酸盐的蔬菜中硝酸盐的绝对生物利用度。在一项开放、四交叉、单剂量研究中，12名人类受试者接受了以下治疗：(1)静脉输注500mg硝酸钠，(2)口服300g煮熟的菠菜，(3)口服300g生生菜，(4)口服300g煮熟的甜菜根。治疗之间的洗脱期至少为6天。分析血浆样本以评估硝酸盐和亚硝酸盐浓度，并计算药代动力学参数。煮熟菠菜中硝酸盐的生物利用度为98±12%，生生菜中为114±14%，煮熟甜菜根中为106±15%。血浆亚硝酸盐浓度没有显著增加。本研究表明，蔬菜中的硝酸盐，无论煮熟与否，都能被非常有效地吸收，导致绝对硝酸盐生物利用度约为100%。因此，减少蔬菜中的硝酸盐含量可能是降低普通人群全身硝酸盐暴露的有效措施。然而，在评估这种措施的有效性时，还需要考虑其他方面，例如生产低硝酸盐含量蔬菜的成本以及蔬菜中硝酸盐可能的有益作用。
