Vitamin D plays a critical role in calcium and phosphate metabolism and helps maintain skeletal integrity in childhood, yet vitamin D status in Chinese children and adolescents is not well documented. The aim of this study was to assess the vitamin D status and analyze the risk factors for vitamin D deficiency in Chinese children and adolescents aged 6–17 years. Serum 25 hydroxyvitamin D (25(OH)D) was measured with a radioimmunoassay kit in 15,000 children and adolescent participants in the Chinese national nutrition and health survey (CNNHS) 2010–2012. Age, gender, region type, ethnicity, outdoor time, and vitamin D supplementation were recorded in unified design questionnaires. The season was recorded by the date of blood taken; location was divided into north and south by China′s Qinling Mountains and Huaihe River; and ambient ultraviolet B (UVB) radiation level was classified according to the corresponding dose of each participant living area from National Aeronautics and Space Administration data. 14,473 participants from the cross-sectional study of CNNHS 2010–2012 were included in this study. The median serum 25(OH)D concentration was 48.2 (35.4–63.4) nmol/L, and the concentration for males was 50.0 (36.5–65.7) nmol/L, which was statistically higher than that of females (46.7 (34.4–60.9) nmol/L) (P < 0.001). The general prevalence of vitamin D deficiency was 53.2%; 50.0% for males and 56.5% for females at the cut-off 50 nmol/L. According to the results of the log-binomial regression analysis, vitamin D deficiency in Chinese children and adolescents was specifically related to female gender (P < 0.0001), to ages 12–14 years (P < 0.0001) and 15–17 years (P < 0.0001), living in large cities (P < 0.0001) or ordinary rural areas (P < 0.0001), low ambient UVB levels (P < 0.0001) and medium ambient UVB levels (P < 0.0001), spring (P < 0.0001), autumn (P < 0.0001) and winter seasons (P < 0.0001). The data showed that vitamin D deficiency was very common among children and adolescents aged 6–17 years in China. Effective sun exposure should be encouraged in both genders aged 6–17 years, dietary vitamin D and vitamin D supplements are also recommended, especially in the seasons of spring and winter.

This paper presents an analysis of the level of blood hemoglobin and the rates of anemia in Chinese rural residents in the 2010–2012 National Nutrition and Health Survey, and the change in its prevalence in rural residents during the last ten years. Our methodology included data from the Chinese Nutrition and Health Surveillance in 2010–2012, where samples were selected through the method of probability proportion to size. The study objects were from 150 sites in provinces, autonomous regions, or municipalities in China. The concentration of blood hemoglobin was determined using the cyanmethemoglobin method. Anemia was judged by the anemia standard recommended by the World Health Organization (WHO), combined with elevation correction standard. The level of blood hemoglobin, the prevalence of anemia, and the 95% CI (Confidence interval) value were analyzed using complex sampling weighted processing, combined with the population figures released by the National Bureau of Statistics in 2009. Our results indicate that the level of blood hemoglobin of the Chinese rural area population was 145.92 ± 0.83 g/L, with the prevalence of anemia in the Chinese rural population at 9.7% (95% CI: 9.4%-10.0%). The prevalence of anemia in children 6-11 years old was 5.5% (95% CI: 5.0%-6.0%), 8.1% (95% CI: 7.5%–8.7%) for 12–17‐year‐old teenagers, 10.0% (95% CI: 9.4%-10.6%) for 18-44‐year‐old adults, 9.6% (95% CI: 9.0%–10.1%) for 45–59‐year‐old adults, and 12.6% (95% CI: 11.9%-13.3%) for the elderly above 60 years old. Our conclusion shows that the prevalence of anemia in the Chinese rural population in 2010–2012 had obviously decreased compared to the last decade; however, women of reproductive age and the elderly still had a high prevalence of anemia.

In this study, we assessed the hemoglobin levels and anemia status of Chinese children and adolescents from the Chinese National Nutrition and Health Survey (CNNHS) in 2010–2012 and analyzed the factors associated with anemia. The hemoglobin concentration and prevalence of anemia for children and adolescents aged 6–17 years from both CNNHS 2010–2012 and CNNHS 2002 were analyzed. Multi-variable logistic regression analysis was used to assess the factors associated with anemia. The mean hemoglobin concentration increased among Chinese children and adolescents, from 135.2 ± 13.9g/L in CNNHS 2002 to 141.2 ± 15.8 g/L in CNNHS 2010–2012, with the prevalence of anemia decreasing from 12.6% to 6.6% (p < 0.0001). Anemia was specifically related to girls (p < 0.0001); children aged 6–8 years (p = 0.0175), 12–14 years (p = 0.0007), and 15–17 years (p < 0.0001); ordinary rural areas (p = 0.0009) and poor rural areas (p < 0.0001);spring (p < 0.0001), autumn (p < 0.0001), and winter (p < 0.0001);underweight individuals (p < 0.0001); and an annual average income per capita of less than 20,000 RMB (p < 0.0001).The prevalence of anemia in Chinese children and adolescents has improved significantly in comparison to 10 years prior; however, it remains a public health problem in this population. Further research is required to understand the determinants of iron status, which could then lead to strategies to alleviate iron deficiency for Chinese children and adolescents, especially for girls, those living in rural areas, underweight individuals, and those with a low family income.

Vitamin D is very important in maintaining children’s bone health because of its regulatory role in calcium and phosphate metabolism. To better understand vitamin D status and related risk factors of children and adolescents in China, this study analyzed the 25-hydroxyvitamin-D (25(OH)D) concentration of children and adolescents aged 6–17 years in China and assessed the risk factors of vitamin D deficiency and insufficiency. We analyzed the data of 25(OH)D concentration collected from the China National Nutrition and Health Survey of Children and Lactating Mothers in 2016–2017 (CNNHS 2016–2017). The age, sex, region type, ethnicities, season, weight and height were recorded, measured by unified questionnaire, equipment and standards. The concentration of 25(OH)D was detected by LC-MS/MS. A total of 64,391 participants from the cross-sectional study of CNNHS in 2016–2017 were included in this study. The median serum 25(OH)D concentration was 17.70 (13.20–22.68) ng/mL, 18.70 (14.10–23.80) ng/mL in boys and 16.60 (12.40–21.40) ng/mL in girls. The total prevalence rate of vitamin D deficiency and insufficiency was 65.98% when the cut-off was 20 ng/mL, 60.42% for boys and 71.99% for girls. According to the results of logistic regression analysis, girls aged above 12 y, living in midlands and northern regions, in spring and winter seasons and with abdominal obesity will have a significantly increased risk of vitamin D deficiency and insufficiency among Chinese children and adolescents. The results showed that vitamin D deficiency and insufficiency are very common among children and adolescents aged 6–17 y in China. They should be encouraged to have more effective sunlight exposure, increased intake of vitamin D from food or supplements in their diet, especially for those aged above 12 y, living in the northern or midlands areas, in spring and winter, and abdominally obese.

Optimal vitamin D (vitD) status is beneficial for both pregnant women and their newborns. The aim of this study was to evaluate the vitamin D status of Chinese pregnant women in the latest China Nutrition and Health Surveillance (CNHS) 2015–2017, analyze the risk factors of vitamin D deficiency (VDD), and compare them with those in CNHS 2010–2012. Serum 25 hydroxyvitamin D (25(OH)D) was measured by ELISA method. City type, district, latitude, location, age, vitamin D supplements intake, education, marital status, annual family income, etc., were recorded. The median 25(OH)D concentration was 13.02 (10.17–17.01) ng/mL in 2015–2017, and 15.48 (11.89–20.09) ng/mL in 2010–2012. The vitamin D sufficient rate was only 12.57% in 2015–2017, comparing to 25.17% in 2010–2012. The risk factors of vitamin D inadequacy (25(OH)D < 20 ng/mL) in 2015–2017 were not exactly consistent with that in 2010–2012. The risk factors included season of spring (p < 0.0001) and winter (p < 0.001), subtropical (p < 0.001), median (p < 0.0001) and warm temperate zones (p < 0.0001), the western (p = 0.027) and the central areas (p = 0.041), while vitD supplements intake (p = 0.021) was a protective factor in pregnant women. In conclusion, vitD inadequacy is very common among Chinese pregnant women. We encourage pregnant women to take more effective sunlight and proper vitD supplements, especially for those from the subtropical, warm and medium temperate zones, the western and the central, and in the seasons of spring and winter.

Anemia is a public health issue for developing countries, especially for women of childbearing age. The aim of this study was to assess the anemia status and analyze the risk factors for anemia in Chinese childbearing women aged 18–49 years. Hemoglobin concentration was measured by the HiCN method in the Fifth Chinese National Nutrition and Health Survey (CNNHS) in 2010–2012. Age, region type, ethnicity, bodyweight, height, education, season and smoke habit were recorded in unified questionnaires. Latitude was divided by China’s Qinling Mountains and Huaihe River. Childbearing women (28,289) from the CNNHS 2010–2012 were included in this study. The median hemoglobin concentration was 136.2(126.6–145.0) g/L, and it was significantly higher than in CNNHS 2002 (132.5 (122.3–141.6) g/L). The prevalence of anemia was 15.0%, and it was significantly lower than 10 years ago. The logistic regression analysis showed anemia in Chinese childbearing women was specifically related to 30–39 age group (P = 0.004), in spring (P < 0.0001) or in winter (P = 0.006), small and medium-sized cities (P = 0.044) and middle school education level (P = 0.027). The results showed that anemia status among childbearing women was greatly improved over 10 years since 2002, but it was still more severe than the rest of the populations. The nutrition propaganda and education is recommended for childbearing women to help them to improve the nutritional status on their own.