中文摘要：

目的了解中国贫困地区18月龄幼儿的维生素B12（VB12）营养状况,以及不同食物干预对幼儿VB12营养状况的影响。方法研究对象来自于一项婴儿辅食的随机对照干预研究。研究对象于6月龄时入组,分别给予免费肉类、强化米粉、普通米粉进行干预,随访至18月龄;18月龄时采集静脉血检测血清VB12、同型半胱氨酸（tHcy）、Hb等,并测量体格生长指标。结果共入选217名18月龄幼儿,其中肉类干预组61名,强化米粉干预组85名,普通米粉干预组71名。217名幼儿的VB12中位数为342（85-2700）pg·mL-1,tHcy中位数为8.20（3.30-20.40）μmol·L-1,Hb中位数为124（90-158）g·L-1。85名（39.2%）VB12〈300pg·mL-1,42名（19.4%）〈200pg·mL-1;26名（12.0%）tHcy〉12μmol·L-1;52名（24.0%）Hb〈115g·L-1。肉类干预组、强化米粉干预组和普通米粉干预组VB12中位数分别为335、422和281pg·mL-1,3组间差异有统计学意义（P=0.013）;3组VB12〈300pg·mL-1的比例分别为肉类干预组39.4%（24名）、强化米粉干预组28.2%（24名）、普通米粉干预组52.1%（37名）,3组间差异有统计学意义（P=0.010）。结论贫困地区幼儿VB12缺乏较普遍,与膳食中VB12摄入不足有关,强化米粉和肉类等干预有助于改善幼儿VB12营养状况。

英文摘要：

Objectives To assess the vitamin B12 nutritional status of 18 months old toddlers in impoverished area of China and to explore its correlation with different complementary foods. Methods Data were drawn from a randomized controlled intervention trial that aimed to investigate the effect of different complementary infant foods. All subjects were recruited at 6 months of age and randomized to feed different complementary foods, meat, fortified cereal, and local made rice cereal. The intervention continued to children at the age of 18 months. The serum vitamin B12, homocysteine, and hemoglobin, as well as anthropometric parameters were measured at 18 months of age. Results A total of 217 toddlers were included in the current analysis, 61 in meat group, 85 in fortified cereal group, and 71 in local made cereal group. The median level of serum vitamin B12 , homocysteine and toddlers was 342（85-2 700） pg·mL-1, 8.20（3.30-20.40） μmol·L-1 and 124（90-158） g·L-1,respectively. 85 （39.2%） toddlers had a serum vitamin B12 level 300 pg·mL-1, 42 （19.4%） toddlers 200 pg·mL-1; 26 （12.0%） toddlers had a homocysteine level 12 μmol·L-1; 52 （24.0 %） toddlers had a hemoglobin level 115 g·L-1. The toddlers in meat, fortified cereal, and local made cereal groups had a median serum vitamin B12 level of 335, 422 and 281 pg·mL-1, respectively. There was statistical difference among three groups （P=0.013）. Among 85 toddlers who had a serum vitamin B12 level 300 pg·mL-1, 39.34% （24） was in meat group, 28.2% （24） in fortified cereal group, and 52.1% （37） in cereal group. There was a significant difference among three groups （P=0.010）. Conclusions Vitamin B12 deficiency was common in toddlers in impoverished area. Inadequate dietary intake was the main reason of vitamin B12 deficiency in these toddlers. Both meat and fortified cereal could improve vitamin B12 nutritional status of toddlers.