母乳喂养婴儿血中25羟胆钙化醇水平与日光照射关系的研究

选择未经维生素D补充的1～8月龄母乳喂养婴儿55名,随机分为两组,实验组鼓励多晒太阳;另一组为自然对照。观察两个月,婴儿膳食仅为母乳、果汁和糖水。户外活动时仅暴露面部和前臂。实验开始时,55名婴儿血中25羟胆钙化醇(25-OH-D))浓度低于参考标准低限11ng/ml者约占20％,X线片可诊断为佝偻病者约占18％。两种诊断指标的符合率为68.6％。乳母血中25-OH-D浓度平均为21.9ng/ml,与其婴儿血中25-OH-D浓度相关系数为0.464,相关非常显著。观察期间,婴儿平均每天户外活动时间实验组为116分钟,对照组为63分钟。实验组实验前后血中25-OH-D浓度为29.7±13.3和38.1±20.0ng/ml,差异显著(P<0.01):对照组为20.6±15.5和19.1±13.4ng/ml前后无差异。两组婴儿血中25-OH-D浓度与各自户外活动计分数呈显著相关(r=0.668和0.631)。后者又与日光紫外线照到体表时间(秒)呈相关(r=0.580)。提示婴儿每周户外活动的计分数在800～1000时,可以维持血中25-OH-D浓度在正常范围。

STUDIES ON ULTRAVIOLET EXPOSURE AND BLOOD 25-OH VITAMIN D IN BREAST-FED INFANTS

We hypothesized that breast-fed infants in China have low vitamin D status and sunshine (UV) exposure may raise serum 25-OH vitamin D (25-OH-D) to normal range. Fifty-five breast-fed term infants (1 to 8 months of age) without vitamin D supplementation were randomly divided into two groups, one being control with usual sunshine exposure (one hour per day), another experimental group with 2-hour exposure per day, in a 2-month study in September and October (month of high sunshine exposure). All of the test infants received only breast milk, rice soup, fruits juice, and mashed vegetables and exposed their face and forearms to the sunshine mostly during the experiment. Nurses monitored the sunshine intensity with a unique infant ultraviolet dosimeter occasionally. Serum 25-OH-D measured by protein binding radioassay revealed that maternal's (22ag/ml) correlated well with that of infan's (r = 0.46). Infant's 25-OH-D ranged from 3 to 61ng/ml at entry with 20% less than ling/ml. Whereas the value of control group decreased from 20.6±15.5 to 19.1±13.4ng/ml after 2-month exposure of 63 minutes per day (P>0.05). the experimental group increased significantly (from 29.7±13.2 up to 38.1±20.0ng/ml, P<0.01) after 2-month exposure of 116 minutes per day. It was suggested that the infants in Beijing may receive sunshine moderately in fall.