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Abstract：
The Biomarkers of Nutrition for Development (BOND) project is designed to provide evidence-informed advice to anyone with an interest in the role of nutrition in health. The BOND program provides information with regard to selection, use, and interpretation of biomarkers of nutrient exposure, status, function, and effect, which will be especially useful for readers who want to assess nutrient status. To accomplish this objective, expert panels are recruited to evaluate the literature and to draft comprehensive reports on the current state of the art with regard to specific nutrient biology and available biomarkers for assessing nutritional status at the individual and population levels. Phase I of the BOND project includes the evaluation of biomarkers for 6 nutrients: iodine, folate, zinc, iron, vitamin A, and vitamin B-12. This review of vitamin A is the current article in this series. Although the vitamin was discovered >100 y ago, vitamin A status assessment is not trivial. Serum retinol concentrations are under homeostatic control due in part to vitamin A\'s use in the body for growth and cellular differentiation and because of its toxic properties at high concentrations. Furthermore, serum retinol concentrations are depressed during infection and inflammation because retinol-binding protein (RBP) is a negative acute-phase reactant, which makes status assessment challenging. Thus, this review describes the clinical and functional indicators related to eye health and biochemical biomarkers of vitamin A status (i.e., serum retinol, RBP, breast-milk retinol, dose-response tests, isotope dilution methodology, and serum retinyl esters). These biomarkers are then related to liver vitamin A concentrations, which are usually considered the gold standard for vitamin A status. With regard to biomarkers, future research questions and gaps in our current understanding as well as limitations of the methods are described.
摘要：
营养发展生物标志物（BOND）项目旨在为任何对营养在健康中的作用感兴趣的人提供循证建议。债券计划提供有关选择的信息，使用,以及对营养素暴露的生物标志物的解释，status,函数,和效果，这对于想要评估营养状况的读者尤其有用。为了实现这一目标，招募专家小组来评估文献，并起草有关特定营养生物学和可用生物标志物的最新技术水平的综合报告，以评估个人和人群水平的营养状况。BOND项目的第一阶段包括评估6种营养素的生物标志物：碘，叶酸,锌，铁,维生素A,和维生素B-12.维生素A的这篇综述是本系列的最新文章。虽然维生素是在100年前发现的，维生素A状态评估并不是微不足道的。血清视黄醇浓度处于稳态控制下，部分原因是维生素A在体内用于生长和细胞分化，并且由于其高浓度的毒性。此外，由于视黄醇结合蛋白（RBP）是一种负急性期反应物，因此在感染和炎症期间血清视黄醇浓度会降低，这使得状态评估具有挑战性。因此，这篇综述描述了与眼睛健康相关的临床和功能指标以及维生素A状态的生化生物标志物(即，血清视黄醇，RBP,母乳视黄醇，剂量反应测试，同位素稀释方法，和血清视黄醇酯）。这些生物标志物与肝脏维生素A浓度相关，这通常被认为是维生素A状态的黄金标准。关于生物标志物，描述了我们当前理解的未来研究问题和差距以及方法的局限性。
