Directly measured free and total 25-hydroxyvitamin D levels in relation to metabolic health in multi-ethnic postmenopausal females in Saudi Arabia

Background: Measurement of free 25-hydroyvitamin D (25(OH)D) status has been suggested as a more representative marker of vitamin D status than that of total 25(OH)D. Previously, free 25(OH)D could only be calculated indirectly; however, a newly developed direct assay for the measurement of free 25(OH)D is now available. The aim of this study therefore was to investigate directly measured total and free vitamin D levels association with metabolic health in postmenopausal healthy women living in Saudi Arabia. Methods: A sample of 302 postmenopausal women aged ≥ 50 years (n=302) living in Saudi Arabia were recruited in a cross-section study design. Blood samples were collected from subjects for measurement of serum levels of total 25(OH)D, directly measured free 25(OH)D, metabolic bone parameters, lipid profile, and other biochemical tests. Results: A positive correlation was found between directly measured free and total 25(OH)D (r=0.64, P<0.0001). Total, but not free 25(OH)D showed significant association with serum intact parathyroid hormone (P=0.004); whilst free 25(OH)D but not total 25(OH)D showed a significant association with total cholesterol and LDL-C (P=0.032 and P=0.045; respectively). Conclusions: Free 25(OH)D and total 25 (OH)D were found to be consistently correlated; but with different associations to metabolic health parameters. Further research is needed to determine which marker of vitamin D status would be the most appropriate in population studies.

Free Vitamin D Status Among Apparently Healthy Adults Living in Duhok Governorate

Serum total 25-OHD is a main marker of vitamin D which represents the intake and sunlight exposure. Free form of 25‐OHD, the small fraction not bound to a transporter protein has been incorporated as a new marker. This cross-sectional study aimed to evaluate the impact of several factors on total and free vitamin D levels in healthy subjects and to find out if the free form of vitamin D could be a better representative of the body’s vitamin D status. Total and free 25‐OHD were analyzed by ELISA method in a blood sample collected from 391 apparently healthy volunteers (219 female and 172 Male) from Duhok Governorate/Iraq population. Total and free 25‐OHD levels were increased proportionally to BMI with lower values seen in the underweight group, also a significant gender differences in total D3 level with higher values in males (23.90 ± 16.41) ng/ml than females (21.24 ± 15.65) ng/ml was observed. Total and Free 25‐OHD levels were significantly associated with ages, their deficiency most frequent occurs in the younger ages between (16–25) years old. Smokers had higher level of Total 25‐OHD (26.95 ± 19.01) ng/ml and Free 25‐OHD (9.47 ± 4.94) pg/ml than nonsmokers (22.14 ± 14.59) ng/ml and (7.87 ± 4.32) pg/ml respectively. A significant increase in Free 25‐OHD level in the veiled women (9.12 ± 4.64) ng/ml than unveiled (6.16 ± 3.73) ng/ml with a significant positive correlation between Free 25‐OHD level and dress style was also seen. 30% and 33% of the participants whom their daily exposure to sunlight for 30 minutes and > 1hour respectively were severe deficient in total 25‐OHD. 95% of the participants who had Abnormally low level of free D were exposed for ≥ 30 minutes to sunlight. Daily exposure to sunlight was negatively associated with Free 25‐OHD level.

Vitamin D Incorporation in Foods: Formulation Strategies, Stability, and Bioaccessibility as Affected by the Food Matrix

Inadequate intake of vitamin D is a global health issue related to severe diseases, mainly involving subjects with dark skin pigmentation, patients affected by malnutrition, malabsorption syndromes, or obesity, and elderly people. Some foods fortified with vitamin D have been tested in vivo, but fortification strategies with a global outreach are still lacking. This review is focused on food fortification with vitamin D, with the aim to collect information on (a) formulation strategies; (b) stability during processing and storage; and (c) in vitro bioaccessibility. Approaches to add vitamin D to various foods were analyzed, including the use of free vitamin D, vitamin D loaded in simple and double nanoemulsions, liposomes, casein micelles, and protein nanocapsules. Numerous studies were reviewed to elucidate the impact of food technologies on vitamin D’s stability, and mechanisms that lead to degradation were identified—namely, acid-catalyzed isomerization, radical-induced oxidation, and photo-oxidation. There is, however, a lack of kinetic data that allow for the prediction of vitamin D’s stability under industrial processing conditions. The roles that lipids, proteins, fibers, and antioxidants play in vitamin bioaccessibility have been clarified in various studies, while future needs include the design of specific food matrices that simultaneously achieve a balance between the long-term stability, bioaccessibility and, ultimately, in vivo functionality of vitamin D.

total and free vitamin D in type 2 diabetes mellitus patients in Baghdad city

Background: The free-form of vitamin D has been used by many researchers as an index of vitamin D status in health and disease. Several methods are there to estimate free, total, and even bioavailable vitamin D. Objective: The present work was carried out to measure free vitamin D using a special formula suggested by Bikle and Schwartz in 2019, which includes the vitamin D binding protein (VDBP). The results will be used to evaluate the vitamin D status in patients with type 2 diabetes mellitus (T2DM), and its relation to the disease progression. Methods: Sixty-four patients with T2DM and 73 healthy subjects, all from Baghdad city, were enrolled in the current study from March to October 2020. For each participant, fasting blood glucose, hemoglobin (HbA1c), insulin resistance HOMA-IR, and body mass index (BMI) were measured in addition to the total vitamin D and VDBP. Moreover, free vitamin D was calculated by the formula of Bikle &amp; Schwartz. Results: There were highly significant correlations between total vitamin D and absolute values of free vitamin D or its percentage. The difference in total vitamin D was significant between patients and healthy controls with no significant change in VDBP, free and bio-available vitamin D, while free vitamin D% was higher in the patient’s group. Correlations between vitamin D and each of BMI, fasting glucose, HbA1c, and HOMA-IR were not significant; however, there was a negative correlation with BMI and fasting glucose in the healthy control subjects only. The Receiver Operating Characteristic (ROC) curve analysis of vitamin D in the diagnosis of diabetes mellitus was poor. Conclusion: Total vitamin D can represent vitamin D status, but it cannot be used as a factor for diagnosing T2DM. However, it could be of importance to change the glycemic status.

Relationship Between Vitamin D and Hormones Important for Human Fertility in Reproductive-Aged Women

Vitamin D deficiency is very common in women of reproductive age. Studies in animals suggests a link between vitamin D and reproductive hormone biosynthesis. A systematic analysis of the correlation of reproductive hormones in reproductive-aged women with both total and free vitamin D was, however, not done so far. This cross-sectional study was performed in 351 healthy reproductive age Caucasian women (median age, 28.0 years; interquartile ranges, 24.7-31.0 years). We measured serum levels of both total and free 25(OH)D, endocrinological, hematological and biochemical parameters. Spearman’s rank correlations were performed to assess the correlation between 25(OH)D metabolites and selected parameters. Total vitamin D and free vitamin D measurements correlated well (rho=0.912, p &lt; 0.0001). Both total 25(OH)D and free 25(OH)D showed significant negative correlation with FAI (rho=-0.229, p&lt;0.0001 and rho=-0.195, p&lt;0.0001 for total and free 25(OH)D, respectively); LH (rho=-0.177, p=0.001 and rho=-0.114, p=0.04 for total and free 25(OH)D, respectively), testosterone (rho=-0.174, p=0.001 and rho=-0.190, p&lt;0.0001 for total and free 25(OH)D, respectively) and AMH (rho=-0.130, p=0.015 and rho=-0.107, p=0.047 for total and free 25(OH)D, respectively). Our study showed comparable correlations of both total and free 25(OH)D with endocrinological parameters, i.e. inverse correlations with free androgen index, luteinizing hormone, testosterone, LH/FSH ratio, androstenedione and anti-Müllerian hormone, and also with hematological and biochemical parameters, i.e. inverse correlations with erythrocytes, hsCRP and leukocytes count, and positive correlation with transferrin saturation, mean corpuscular hemoglobin and mean corpuscular volume in healthy reproductive age women.

Understanding the role of emerging vitamin D biomarkers on short-term persistence of high-risk HPV infection among mid-adult women

Background Associations between vitamin D biomarkers and persistent high-risk human papillomavirus (hrHPV) detection have not been evaluated. Methods 2011-2012 stored sera from 72 women ages 30-50 years with prevalent hrHPV (n=116 type-specific infections) were tested for 5 vitamin D biomarkers: 25(OH)D and 4 emerging biomarkers, 1,25(OH)2D, 24,25(OH)2D, free vitamin D, and vitamin D binding protein (DBP). hrHPV detection patterns (persistent versus transient/sporadic) were determined using cervicovaginal swabs collected monthly for 6 months. Associations between vitamin D and short-term type-specific hrHPV persistence were estimated using logistic regression. Our primary exposure was continuous 25(OH)D, with additional biomarkers evaluated as secondary exposures. Primary models adjusted for age, race, BMI, education, contraceptives, smoking, season, and calcium/phosphate levels. Sensitivity analyses restricted from 19 hrHPV types to 14 used in cervical cancer screening. Results In primary analyses, non-significant positive associations with hrHPV persistence were observed for measures of 25(OH)D and 24,25(OH)2D. Associations were stronger and significant restricting to 14 hrHPV types (25(OH)D per 10ng/mL increase: aOR=1.82,95%CI:1.15-2.88 and aOR=4.19,95%CI:1.18-14.88 DBP-adjusted; 25(OH)D≥30 vs &lt;30ng/mL: aOR=8.85,95%CI:2.69-29.06; 24,25(OH)2D: aOR=1.85,95%CI:1.18-2.88). 1,25(OH)2D was unassociated with persistence. Conclusions Serum vitamin D measured by multiple biomarkers showed positive associations with short-term hrHPV persistence that were significant only when restricting to 14 clinically-relevant hrHPV types.