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[Exploring study on the cutoff of vitamin D deficiency in Chinese adults]
Yichun Hu1, Siran Li1, Zhen Liu1
1Key Laboratory of Trace Element Nutrition NHFPC, National Institute for Nutrition and Health, Chinese Center for Disease Control and Prevention, Beijing 100050, China.
Objective:
To study the relationship between 25-hydroxyvitamin D [25(OH)D] concentration and intact parathyroid hormone(iPTH) concentration in the Chinese non-clinical population aged 18-44 y, and to explore the threshold value of determining the appropriate nutritional status of vitamin D.
Methods:
A total of 650 plasma samples of adults aged 18-44 years old were selected from the established biological samples' bank of Chinese Chronic Diseases and Nutrition Survey(CCDNS, 2015-2018). Basic information(including age, gender, region type, season, etc. ) was collected by questionnaires, and the waist circumference, height and weight of the subjects were determined unified. North and South area was divided by Qinling Mountains and Huaihe River. The serum 25(OH)D concentration was determined by high performance liquid chromatography tandem mass spectrometer, and the iPTH was determined by electronic chemiluminescence method. The relationship of 25(OH)D and iPTH were analyzed by partial correlation analysis, and the threshold of 25(OH)D was analyzed by locally weighted scatter plot smoothing method after adjusting the iPTH by age, season of blood draw, BMI, waist, sex and latitude.
Results:
A total of 623 serum samples(293 male, 330 female) of 25(OH)D concentration and iPTH concentration were analyzed after excluding samples with poor blood sample quality. Significant higher 25(OH)D concentration was found in male than female(P<0. 0001). And the samples from the southern China had higher 25(OH)D concentration than those from the northern China(P<0. 0001). Samples from autumn had higher 25(OH)D concentration than those from spring and winter(P<0. 0001). The 25(OH)D concentration of samples from cities was lower than that of rural areas(P=0. 018). The inversely relationship between 25(OH)D concentration and iPTH concentration was observed when the 25(OH)D was below 17. 6 ng/mL for both sexes. The threshold of 25(OH)D for male was 16. 2 ng/mL and it was 25. 6 ng/mL for female.
Conclusion:
The threshold and the relationship between 25(OH)D and iPTH differs by sex among Chinese adults aged 18-44 y. Further study is needed to evaluate the sex-specific ranges of optimal vitamin D.
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