Vitamin D is essential for bone health. Vitamin D deficiency causes rickets and osteomalacia. In non-Western immigrants in the Netherlands, low vitamin D status is common. For example, low... Show moreVitamin D is essential for bone health. Vitamin D deficiency causes rickets and osteomalacia. In non-Western immigrants in the Netherlands, low vitamin D status is common. For example, low concentrations of 25-hydroxyvitamin D have been reported among Turkish, Moroccan, Surinamese, and sub-Saharan African populations. However, little is known about the vitamin D status of Chinese in the Netherlands. Therefore, this thesis aimed to determine the vitamin D status of a Chinese population in the Netherlands, and examined determinants of low 25-hydroxyvitamin D concentrations. Also, associations between 25-hydroxyvitamin D and bone, cardio-metabolic outcomes, and genetic factors were examined. Finally, a patient-friendly method to assess 25-hydroxyvitamin D concentration was investigated. The main result was that serum 25-hydroxyvitamin D concentration of our study population (42-46 nmol/L) appeared to be lower than that of ethnic Dutch (60-67 nmol/L), but better than other non-Western immigrant groups in the Netherlands (24-38 nmol/L), as previously found by others. Almost one-quarter of our study population, however, did not meet the requirement for an adequate vitamin D status of the Health Council of the Netherlands (Gezondheidsraad). Therefore, public health authorities and health care providers should continue to make efforts to improve the vitamin D status of non-Western immigrants. Show less
Blood for determining 25-hydroxyvitamin D-3 [25(OH)D-3] is usually obtained through venipuncture although, as an alternative for serum, dried blood spot (DBS) can be considered. The aim of this... Show moreBlood for determining 25-hydroxyvitamin D-3 [25(OH)D-3] is usually obtained through venipuncture although, as an alternative for serum, dried blood spot (DBS) can be considered. The aim of this proof-of-concept study was to investigate levels of agreement between measurements of 25(OH)D-3 obtained with DBS compared with serum. 301 Chinese participants were included who completed 25(OH)D-3 measurement from DBS and from simultaneously collected blood samples obtained by venipuncture. Measurements of both DBS and serum 25(OH)D-3 were performed using liquid chromatography followed by tandem mass spectrometry. Agreement between the two methods was assessed with Passing and Bablok regression analysis and Bland-Altman plot.Measurements showed a good correlation (Pearson's correlation coefficient r = 0.929, P < 0.001) between the two methods. After recalculating for a 13% difference, a regression equation of DBS 25(OH)D-3 = -1.91 + 1.00 serum 25(OH)D-3 was found in Passing and Bablok regression analysis. Bland-Altman analysis showed a fixed bias of 1.7 nmol/L; upper and lower limit of agreement was 24.1 nmol/L and -20.7 nmol/L, respectively.Sensitivity of recalculated DBS for 25(OH)D-3 concentrations < 30 and < 50 nmol/L was 87.8% and 91.1%, respectively, and specificity was 89.2% and 83.1%, respectively.In conclusion, a good agreement was found between the measurement of 25(OH)D-3 obtained with DBS compared with serum. DBS may possibly be used in a future screening program, but it is less suitable for individualized vitamin D status assessment. Show less
Blood for determining 25-hydroxyvitamin D3 [25(OH)D3] is usually obtained through venipuncture although, as an alternative for serum, dried blood spot (DBS) can be considered. The aim of this proof... Show moreBlood for determining 25-hydroxyvitamin D3 [25(OH)D3] is usually obtained through venipuncture although, as an alternative for serum, dried blood spot (DBS) can be considered. The aim of this proof-of-concept study was to investigate levels of agreement between measurements of 25(OH)D3 obtained with DBS compared with serum. 301 Chinese participants were included who completed 25(OH)D3 measurement from DBS and from simultaneously collected blood samples obtained by venipuncture. Measurements of both DBS and serum 25(OH)D3 were performed using liquid chromatography followed by tandem mass spectrometry. Agreement between the two methods was assessed with Passing and Bablok regression analysis and Bland-Altman plot. Measurements showed a good correlation (Pearson’s correlation coefficient r=0.929, P < 0.001) betweenthe two methods. After recalculating for a 13% difference, a regression equation of DBS 25(OH)D3 = -1.91+1.00 serum 25(OH)D3 was found in Passing and Bablok regression analysis. Bland-Altman analysis showed a fixed bias of 1.7 nmol/L; upper and lower limit of agreement was 24.1 nmol/L and -20.7 nmol/L, respectively. Sensitivity of recalculated DBS for 25(OH)D3 concentrations<30 and<50 nmol/L was 87.8% and 91.1%, respectively, and specificity was 89.2% and 83.1%, respectively. In conclusion, a good agreement was found between the measurement of 25(OH)D3 obtained with DBS compared with serum. DBS may possibly be used in a future screening program, but it is less suitable for individualized vitamin D status assessment. Show less
Introduction: Vitamin D is essential for bone health since it stimulates the intestinal absorption of calcium and phosphorus from the gut, both necessary for bone mineralization. However, vitamin D... Show moreIntroduction: Vitamin D is essential for bone health since it stimulates the intestinal absorption of calcium and phosphorus from the gut, both necessary for bone mineralization. However, vitamin D deficiency is highly prevalent among several non-Western immigrant populations in the Netherlands. To date, there are no data available of the vitamin D status in the Chinese population residing in the Netherlands. Therefore, an observational study was performed to determine 25-hydroxyvitamin D (25(OH)D) concentrations and to assess potential determinants of low vitamin D status. Methods: Subjects, aged 18 years and older, with a Chinese background and residing in the Netherlands were invited to participate in the study. A questionnaire was used to assess general characteristics and lifestyle habits. Fasting blood samples were obtained in March 2014 to measure serum 25(OH)D concentration, and analysed by liquid chromatography tandem mass spectrometry. Results: 418 subjects participated in the study, 104 men and 314 women. The mean age for both men and women was 56 years. Serum 25(OH)D concentration < 50 nmol/L was more prevalent in men than in women (67.9% and 53.1%, respectively; p = 0.008). The percentage of serum 25(OH)D concentration < 25 nmol/L in men and women was 5.8% and 10.9%, respectively. Multiple logistic regression analysis, adjusted for age and gender, revealed that non-use of vitamin D supplements and fewer days per week of physical activity were significant predictors of serum 25(OH)D levels below 50 nmol/L. Conclusions: Within the Chinese population living in the Netherlands, serum 25(OH)D concentration was below 50 nmol/L in 68% of men and 53% of women. Use of vitamin D supplements by Chinese people in the Netherlands was highly protective against low 25(OH)D levels. Show less
Low vitamin D status is associated with low bone mass which, in turn, is an important predictor of fracture. However, data on this relationship in non-Caucasian populations are scarce. This review... Show moreLow vitamin D status is associated with low bone mass which, in turn, is an important predictor of fracture. However, data on this relationship in non-Caucasian populations are scarce. This review shows such an association in the Chinese population in five of the 11 included studies.INTRODUCTION: In the elderly population, the serum 25-hydroxyvitamin D [25(OH)D] concentration is often inadequate. This may cause a lower bone mineral density (BMD), which is an important predictor of fracture. It is estimated that by 2050 more than half of all hip fractures worldwide will occur in Asia. However, data on the relationship between vitamin D status and BMD in a non-Caucasian population are scarce. Therefore, this study reviews the literature on the relationship between serum 25(OH)D and BMD in the Chinese population.METHODS: A search was made in PubMed, EMBASE, Web of Science and Cochrane Library (up to December 2014) to identify relevant studies using the terms vitamin D status, bone mineral density, and Chinese.RESULTS: Of the 293 studies identified, 11 fulfilled the inclusion and exclusion criteria and were analyzed. Mean serum 25(OH)D concentrations ranged from 29-82 nmol/L. In 5 of the 11 studies, an association was found between vitamin D status and BMD in the Chinese population.CONCLUSION: The evidence for a relationship between the serum 25(OH)D concentration and BMD in the middle-aged and elderly Chinese population living in Asia appears to be limited and inconsistent. Show less
