Total and free vitamin D status among apparently healthy adults living in Duhok Governorate

Vitamin D levels in Portuguese Navy military personnel: a cross-sectional study

OBJECTIVES

Evaluate vitamin D levels in Portuguese active-duty Navy military personnel during winter and explore the relationship between Navy occupational settings and vitamin D levels, as well as between vitamin D levels and fatigue, sleep health, and burnout.

METHODS

All active-duty Navy military personnel who collected a blood sample at the Naval Medicine Centre during the winter of 2023-2024 were included in a cross-sectional study. Serum 25-hydroxy-vitamin D (25(OH)D), calcium, phosphorus and parathyroid hormone were added to their analysis request. They were asked to complete a questionnaire that included questions about work, sun exposure, vitamin D-rich foods and/or vitamin D supplements or medication intake, fatigue, sleep health and burnout. Blood samples were processed at the Clinical Pathology Service of the Portuguese Armed Forces Hospital. T-test/median test and z-test were applied to compare homologous means/medians and prevalences, respectively.

RESULTS

Of the 735 participants, 42.2%, 41.1% and 16.7% were vitamin D deficient, insufficient and sufficient, respectively. The median serum 25(OH)D level was significantly lower (p<0.001), and vitamin D deficiency prevalence was significantly higher (p=0.000) in 'onboard' and 'indoors' groups, as well as in the 'mixed shifts' group (p=0.030; p=0.004). Median serum 25(OH)D level was not statistically different between groups with and without fatigue, poor sleep health, and personal or work-related burnout.

CONCLUSIONS

The high prevalence of vitamin D deficiency in a sample of Portuguese active-duty Navy military personnel, during winter, especially those working onboard, indoors and with mixed shifts, must be addressed by Navy occupational health services. Future research should include submariners.

Vitamin D deficiency or resistance and hypophosphatemia

Vitamin D is mainly produced in the skin (cholecalciferol) by sun exposure while a fraction of it is obtained from dietary sources (ergocalciferol). Vitamin D is further processed to 25-hydroxyvitamin D and 1,25-dihydroxy vitamin D (calcitriol) in the liver and kidneys, respectively. Calcitriol is the active form which mediates the actions of vitamin D via vitamin D receptor (VDR) which is present ubiquitously. Defect at any level in this pathway leads to vitamin D deficient or resistant rickets. Nutritional vitamin D deficiency is the leading cause of rickets and osteomalacia worldwide and responds well to vitamin D supplementation. Inherited disorders of vitamin D metabolism (vitamin D-dependent rickets, VDDR) account for a small proportion of calcipenic rickets/osteomalacia. Defective 1α hydroxylation of vitamin D, 25 hydroxylation of vitamin D, and vitamin D receptor result in VDDR1A, VDDR1B and VDDR2A, respectively whereas defective binding of vitamin D to vitamin D response element due to overexpression of heterogeneous nuclear ribonucleoprotein and accelerated vitamin D metabolism cause VDDR2B and VDDR3, respectively. Impaired dietary calcium absorption and consequent calcium deficiency increases parathyroid hormone in these disorders resulting in phosphaturia and hypophosphatemia. Hypophosphatemia is a common feature of all these disorders, though not a sine-qua-non and leads to hypomineralisation of the bone and myopathy. Improvement in hypophosphatemia is one of the earliest markers of response to vitamin D supplementation in nutritional rickets/osteomalacia and the lack of such a response should prompt evaluation for inherited forms of rickets/osteomalacia.

Determination of vitamin D status in singleton and twin gestations using CLIA and LC-MS/MS

Objective

Vitamin D plays an important role during pregnancy. The aim was to compare vitamin D status in a group of singleton (SP) and twin pregnancies (TP) using two diagnostic methods: chemiluminescence immunoassay (CLIA) and liquid chromatography with tandem mass spectrometry (LC-MS/MS).

Design

This is a cross-sectional study.

Methods

The study was conducted in the population of SP and TP at the gestational age above 20 + 0 at the Bielanski Hospital in Warsaw, Poland, between October 2020 and January 2023. All patients had their venous blood samples collected and were given an original survey containing questions on demography and vitamin D supplementation.

Results

The study group included 53 Caucasian women with SP and 78 with TP aged from 21 to 47. Considering LC-MS/MS, patients with TP had lower concentrations of 25-hydroxyvitamin D (25(OH)D) than patients with SP. However, no significant difference was observed in the frequency of the occurrence of vitamin D deficiency (25(OH)D < 30 ng/mL). In both groups, the levels obtained with CLIA were significantly lower than in case of LC-MS/MS, however, strongly correlated. The intermethod agreement accounted for 52.4% and the Cohen's kappa coefficient was 0.142.

Conclusions

The concentration of 25(OH)D in pregnant women depends on the type of gestation (SP/TP) and on the diagnostic methods used (CLIA/LC-MS/MS). Based on LC-MS/MS, the incidence of vitamin D deficiency was low in our group and no differences occurred in its frequency between SP and TP. The intermethod agreement between CLIA and LC-MS/MS on the detection of vitamin D deficiency was low.

Significance statement

This is the first study to compare the concentration of 25(OH)D levels between SP and TP using two methods: CLIA and the gold standard - LC-MS/MS. Based on LC-MS/MS, a low incidence of vitamin D deficiency was observed in our group, in which the vast majority of patients took cholecalciferol supplements. Moreover, there were no differences in its frequency between SP and TP. However, the 25(OH)D level was significantly lower in TP. The intermethod agreement between CLIA and LC-MS/MS on the detection of vitamin D deficiency was low, which is associated with substantial clinical implications.

Vitamin D status among residents of Molidawa Daur Autonomous Banner, Inner Mongolia, North China

OBJECTIVES

To retrospectively analyze the vitamin D (VD) status of residents in northeastern Inner Mongolia and its relationship with the average monthly sunshine hours.

METHODS

Serum 25-hydroxyvitamin D[s-25(OH)D] samples from 4982 outpatients (2092 males) in Moli Dawa Daur Autonomous Banner People's Hospital, Hulunbuir, China from July 2018 to January 2022 were included in this study.

RESULTS

The overall median s-25(OH)D was 53.3 nmol/L, VD deficiency (<30 nmol/L), deficiency (30-50 nmol/L), sufficient (>50-250 nmol/L) and excess (>250 nmol/L) were 16% (796/4982), 30% (1495/4982), 53.4% (2658/4982) and 0.7% (33/4982). There were statistically significant differences in median s-25(OH)D by month, age-groups and gender (p<0.001). Low VD status (LVDS, including VD deficiency and insufficiency) in females was 54.6% and males was 33.9%, and the LVDS composition differed significantly by age-group and month (p<0.05). The changing trend of the median s-25(OH)D level was similar to the monthly average sunshine hours, with a slight lag.

CONCLUSION

Nearly half of residents live in LVDS. LVDS is affected by month, gender, and age.

Determination of a Serum 25-Hydroxyvitamin D Reference Ranges in Japanese Adults Using Fully Automated Liquid Chromatography-Tandem Mass Spectrometry

BACKGROUND

Despite an increasing interest in vitamin D status, a reference range of the nutrient has not been fully established. This is partly due to a paucity of standardized measuring systems with high throughput. In addition, the range may vary by populations and may change with modernization of lifestyles.

OBJECTIVES

This study aims to calculate the current reference concentration of 25-hydroxyvitamin D (25(OH)D) among healthy people living in an urban area in Japan.

METHODS

A newly developed fully automated liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) system was used to measure serum 25(OH)D concentrations. Reproducibility was assessed by measuring standardized samples. Accuracy was validated by comparing with commercially available immunoassays. Then, mass screening was conducted targeting participants who received medical checkups in Tokyo from April 2019 to March 2020, and the reference ranges were calculated.

RESULTS

The coefficients of variations of interoperator and interday reproducibility were 4.1%-8.5% and 3.7%-8.0% for 25-hydroxyvitamin D₂ (25(OH)D2) and 4.7%-7.0% and 4.0%-6.9% for 25-hydroxyvitamine D3, respectively. The measured total 25(OH)D concentrations correlated well with those measured by immunoassays. In total, 5518 participants were measured for 25(OH)D concentrations, among whom 98% showed inadequate concentrations (<30 ng/mL). The reference ranges of total 25(OH)D for female, male, and total participants were 7-30 ng/mL, 5-27 ng/mL, and 6-29 ng/mL, respectively. After excluding those with abnormal renal and liver function, the range was 6-30 ng/mL.

CONCLUSIONS

The high prevalence of vitamin D insufficiency among seemingly healthy population may be attributed to lifestyle characteristics of people living in urban areas of Japan, including spending less time outdoors and lower intake of traditional foods. Longitudinal follow-up and mass screenings targeting different population will help elucidate reasons for discrepancies between official guidelines and the observed concentrations, to which the well-validated measurement system is essential.

Association Between Vitamin D Level and Z-Score Changes of Bone Density in College-Age Saudi Girls: A Cross-Sectional Study

Objective

Vitamin D (VD) deficiency is a worldwide health problem. VD plays a crucial role in calcium homeostasis, phosphorus metabolism and bone health. Still much remain to understand the effect of VD deficiency on bone mass. This study aimed to evaluate the relationship between VD levels and bone mass density (BMD) among college-age Saudi females.

Methods

In a cross-sectional study, 460 females with a median age of 21 years, were enrolled, completed a comprehensive, structured questionnaire which was validated by experienced endocrinologist, a dietician, and a statistician. Body mass indexes (BMI) were calculated, and BMD was estimated through quantitative ultrasound to ankle. Serum VD, calcium, phosphate, parathyroid hormone, and alkaline phosphatase were measured using chemiluminescent immunoassay technique.

Results

VD deficiency reached up to 83.3% (66.9% insufficiency and 16.4% deficiency). Lower than normal BMD was detected in 18.3% of subjects, with only 1.1% having a non-age-matched high risk for osteoporosis. The significant independent predictors of Z-score were age of menarche, menstrual irregularities, dairy products consumption, physical activity, BMI, alkaline phosphatase, and history of previous VD supplementation.

Conclusion

VD deficiency and low BMD are highly prevalent among college-age Saudi females. Low BMD is not linked to serum level of VD but to its previous use as a supplementation. Early lifestyle changes, attention to gynecological problems, and prevention of VD deficiency are all needed to support BMD among these girls.