Determinants of serum levels of vitamin D: a study of life-style, menopausal status, dietary intake, serum calcium, and PTH

Combined Oral Contraceptives: Association with Serum 25-Hydroxyvitamin D and Calcium and Bone Homeostasis

Background: Use of combined oral contraceptives (COCs) has been found to increase serum 25-hydroxyvitamin D [25(OH)D] but effects on calcium and bone homeostasis are unclear. Materials and Methods: Serum 25(OH)D, parathyroid hormone (PTH), alkaline phosphatase (ALK) and estradiol, dietary intake of bone-related nutrients and foods, bone mineral density (BMD), and body fat were compared in adult women (20-35 years; body mass index 21.5 ± 2.3 kg/m2) users (+COC, n = 32) and nonusers (-COC, n = 20) of COC. Biochemical markers were measured by automated assays. BMD at total body (TB), lumbar spine (LS), femoral neck (FN) and trochanter (TR), and body fat, were measured by dual-energy X-ray absorptiometry. Dietary intake was assessed by a food frequency questionnaire. Results: Intake of calcium, dairy foods, and fruits and vegetables, were adequate and did not differ by COC. Mean 25(OH)D was 35% higher in +COC (110.4 ± 27.3 nmol/L, 44.2 ± 1.8 ng/mL) compared with -COC (81.7 ± 22.8 nmol/L, 32.7 ± 2.3 ng/mL; p < 0.001). Mean PTH, ALK, and estradiol were 28%, 12%, and 62% lower, respectively, in +COC compared with -COC (p ≤ 0.05). Mean BMD z-scores (all sites) were adequate and did not differ by COC. There were no correlations between 25(OH)D and dietary, biochemical, and body composition variables. PTH was inversely correlated with TR-BMD z-score in -COC (r = -0.47; p = 0.04), and ALK was inversely correlated with TB-, TR-, and LS-BMD z-scores in -COC (r ≤ -0.43; p ≤ 0.04), but not in +COC. Conclusions: Increased serum 25(OH)D with COC use was paralleled by expected physiologic adjustments in calcium and bone homeostasis, and adequate bone mass status, in nonobese young adult women consuming bone-healthy diets.

Patterns of 25-Hydroxyvitamin D3, Calcium Status, and Anemia in the Saudi Population: A Cross-Sectional Study

BACKGROUND

Emerging evidence suggests an intricate relationship between vitamin D, Ca²⁺, and inflammation-driven anemia. We, thus, investigated the patterns of serum 25(OH)D₃, Ca²⁺, ferritin, and iron in healthy and anemic members of the Saudi population.

METHODS

A population-based, retrospective, cross-sectional study was designed to analyze data for 14,229 subjects, aged 3-110 years, obtained from Al-Borg Medical Laboratories, over a six-year period (2014-2020). Gender and age differences were analyzed for 25(OH)D₃, Ca²⁺, hemoglobin, ferritin, and iron.

RESULTS

Vitamin D deficiency was extremely prevalent (98.47%) irrespective of age or gender, despite an increasing trend with age, in clear contrast to serum Ca²⁺. Ferritin was significantly lower in young adult and adult females, compared to elderly females, whereas iron was significantly reduced in females; in particular, adult females compared to young adults or elderly adults. Only anemic adult males had significantly lower 25(OH)D₃, while Ca²⁺ was consistently significantly diminished in anemics of all age groups, independent of gender. Notably, hypocalcemic subjects were 2.36 times more likely to be anemic. Moreover, ferritin, but not iron, was significantly diminished in anemics, which was only evident in young adults and adults. However, both ferritin and iron showed positive correlation with hematocrit, hemoglobin, MCH, MCHC, and MCV.

CONCLUSIONS

Despite being significantly lower in anemics, 25(OH)D₃ is not particularly associated with anemia, while hypocalcemia is associated with an increased risk for anemia. Assessment of vitamin D and Ca²⁺ status may be valuable in the clinical management of anemia in the Saudi population.

The Study of the Association of Serum Parathyroid Hormone Level with Obesity in Patients Admitted to a Tertiary Care Center in Basrah

Background: Parathyroid hormone (PTH) has been reported to have a positive correlation with insulin resistance and the development of the metabolic syndrome. This study aims to evaluate if there is an association between obesity and serum PTH levels. Methods: This case-control study was conducted at the Faiha Specialized Diabetes Endocrine and Metabolism Center in Basrah (Southern Iraq) from September 2018 to July 2019. A total of 230 patients were recruited for this study (103 male and 127 female), divided into 2 groups according to the BMI: <30 kg/m2 were considered as the control group (83 persons) and ≥30 kg/m2 were considered as obese persons (147 persons). The study groups were also subdivided into 3 groups according to the serum level of PTH: <40 pg/mL, 40–65 pg/mL, and >65 pg/mL. Results: The mean age of the obese and control groups was 44.39 ± 10.64 and 30.12 ± 8.95 years, respectively. About 46.25% of obese were men and 53.75% were women, while 42% of the control group were men and 58% were women. Serum PTH level was significantly higher (p < 0.001) among obese persons with a mean level of 53.21 ± 19.58 pg/mL for obese and 37.63 ± 21.8 pg/mL for control. Vitamin D deficiency was seen in 84.4% of the obese group while in 71.1% of the control group (p value 0.04). Females turned to have higher PTH levels than males in both the obese and the control group (p value <0.001). However, age and the presence of diabetes mellitus were not associated with higher PTH levels (p value 0.155 and 0.6, respectively). Conclusion: Obesity was associated with a higher serum PTH level related to the severity of vitamin D deficiency.

Early-onset climacterium is not associated with impaired vitamin D status: a population-based study

OBJECTIVE

To investigate vitamin D status in women with the onset of the climacteric phase by age 46 as both early menopause and inadequate vitamin D status may increase the risk of adverse health outcomes.

METHODS

A cross-sectional study included 2,544, 46-year-old women from a birth cohort. Women were divided into the following two groups according to their menstrual history and follicle-stimulating hormone (FSH) concentration: 1) climacteric (FSH ≥25 IU/L and amenorrhea ≥4 mo, n = 351) and 2) preclimacteric women (FSH <25 IU/L and having regular/irregular menstrual cycles, n = 2,193). Serum 25-hydroxyvitamin D (25(OH)D) concentrations were compared between the groups. A linear regression model was performed to investigate which factors are associated with 25(OH)D status.

RESULTS

Mean serum 25(OH)D concentrations were higher in climacteric compared with preclimacteric women (68.1 ± 19.8 nmol/L vs 65.2 ± 19.3 nmol/L, P = 0.01). However, in the linear regression model, climacteric status was not associated with 25(OH)D status (multivariable adjusted mean difference 4.5 nmol/L, 95% confidence interval -1.4 to 10.4, P = 0.137). A total of 76 of the climacteric women were using systemic estrogen hormone therapy (HT). In a subanalysis, including only climacteric women, the use of HT was associated with higher 25(OH)D status (multivariable adjusted mean difference 5.9 nmol/L, 95% confidence interval 1.3-10.5, P = 0.013).

CONCLUSIONS

The onset of the climacteric phase by age 46 was not associated with inadequate 25(OH)D concentrations, whereas HT use was associated with higher 25(OH)D status in women with early-onset climacterium.

Serum Iodine and Breast Cancer Risk: A Prospective Nested Case-Control Study Stratified for Selenium Levels

BACKGROUND

Iodine has been suggested to protect against breast cancer, but there are no epidemiologic studies on individual risk. An interesting finding is that in areas where the exposure to both selenium and iodine are high (e.g., Japan), the risk of breast cancer is lower than in areas where selenium is high and iodine low (e.g., United States), or in areas where both are low (e.g., Northern Europe). The aim of this study was to investigate the association between prediagnostic serum iodine levels and subsequent breast cancer risk, and to investigate if this potential association was modified by selenium levels.

METHODS

The Malmö Diet and Cancer Study provided prediagnostic serum samples and the current analysis included 1,159 breast cancer cases and 1,136 controls. Levels of baseline serum iodine and selenium were analyzed. A logistic regression analysis yielded ORs with 95% confidence intervals adjusted for potential confounders.

RESULTS

There was no evidence of an overall association between iodine levels and risk of breast cancer. Among women with high selenium levels (above the median), high iodine levels were associated with a lower risk of breast cancer; the OR for above versus below the median was 0.75 (0.57-0.99). The corresponding OR for women with low selenium was 1.15 (0.87-1.50), and the P _interaction was 0.06.

CONCLUSIONS

The combination of high serum iodine levels and high selenium levels was associated with a lower risk of breast cancer.

IMPACT

A high iodine and selenium exposure may decrease the risk of breast cancer.

Vitamin D deficiency associated with reproductive factors in northern Iranian women: The PERSIAN Guilan Cohort Study (PGCS)

BACKGROUND

One of the public health concerns is Vitamin D deficiency. The aim of this study was to determine the prevalence of vitamin D inadequacy and to determine its reproductive factor correlates in northern Iranian women.

METHODS

This study, conducted on 5096 females aged 35-70 years. The study was based on data from PERSIAN Guilan Cohort Study (PGCS), a prospective, population-based cohort study in Guilan, Iran. History of reproductive and gynecologic factors, including age at menarche, age at first marriage, number of pregnancies or live births, age at first pregnancy, duration of breastfeeding, number of abortions, age and type of menopause status, use of oral contraceptives or hormone replacement therapy, history of hysterectomy, tubectomy or oophorectomy and history of gestational diabetes and hypertension was collected. Serum 25(OH) vitamin D was measured.

RESULTS

The mean 25(OH)-D concentration was 21.78 ng/mL, and 53.5% of women had vitamin D inadequacy. The multivariate analyses revealed that younger age (36-45 years) [>66 years adjusted odds ratio (aOR) = 2.1, 95% CI 1.7-2.7, 56-65 years aOR = 1.7, 95% CI 1.3-2.1 and 46-55 years aOR = 1.4, 95% CI 1.1-1.7], not consuming oral contraceptives [aOR = 1.1, 95% CI 1.05-1.3] and pre-menopausal status [aOR = 1.4, 95% CI 1.2-1.6] were significantly independently associated with vitamin D inadequacy.

CONCLUSION

Vitamin D inadequacy is common in northern Iranian women. The reproductive factors that independently correlated with vitamin D statues are oral contraceptive consumption and menopausal statue.

Association between Body Fatness and Vitamin D3 Status in a Postmenopausal Population

Vitamin D is a micronutrient that plays a key role in phosphocalcic metabolism. The postmenopausal population presents a risk of deficiency in this vitamin due to hormonal alterations which, in the case of obesity, would be exacerbated. The objective was to assess the status of vitamin D in a postmenopausal population and determine the relationship of 25-hydroxivitamin D [25(OH)D] and its metabolites with anthropometric parameters. The study included 78 healthy postmenopausal women aged from 44 to 76. The nutrient intake assessment was carried out using the 24 h reminder (R24h). 25(OH)D was analyzed using ultra-high-performance liquid chromatography (UHPLC). A total of 80% and 68% of the women studied did not reach sufficient values of 25(OH)D and 25-hydroxivitamin D₃ [25(OH)D₃], respectively, which was inversely correlated with Body Mass Index (BMI) (r = −0.25, p = 0.04), hip perimeter (r = −0.26 and r = −0.24, all p < 0.05), arm circumference (r = −0.29, p = 0.01) and fat mass (r = −0.28 and r = −0.26, all p < 0.05). 25(OH)D₃ is the metabolite that contributed most to this association. In conclusion, 25(OH)D₃ levels are related to anthropometric parameters in the postmenopausal women in this study, confirming insufficient status in the majority of the population. Approach strategies are necessary to correct and avoid this risk in order to ensure future quality of life.

Vitamin D and the skin: what should a dermatologist know?

Although first discovered in 1931, vitamin D has seen an increased interest in the scientific community over the past decades, including the dermatology field. Vitamin D promotes calcium and phosphorus absorption; however, the actions of vitamin D are not confined to bone. Indeed, there is now overwhelming and compelling scientific data that vitamin D plays a crucial role in a plethora of cellular function and in extra-skeletal health. Except for fatty fish livers, very few foods naturally contain vitamin D; and the major source of vitamin D comes from skin exposure to sunlight via ultraviolet B. Keratinocytes are unique in the body as not only do they provide the primary source of vitamin D for the body, but they also possess both the enzymatic machinery to metabolize the vitamin D produced to active metabolites. This has been referred to as the photoendocrine vitamin D system. Vitamin D regulates keratinocytes proliferation and differentiation; and plays a role in the defense against opportunistic infections. Multiple factors are linked to vitamin D status; and a growing number of dermatologic diseases has been linked to vitamin D status such as atopic dermatitis, psoriasis, vitiligo, and cutaneous cancers. In this article, we reviewed the potential determinants of vitamin D status, as its implications in dermatologic diseases.

Predicting serum vitamin D concentrations based on self-reported lifestyle factors and personal attributes

Evidence supports the role of vitamin D in various conditions of development and ageing. Serum 25-hydroxyvitamin D (25(OH)D) is the best indicator for current vitamin D status. However, the cost of its measurement can be prohibitive in epidemiological research. We developed and validated multivariable regression models that quantified the relationships between vitamin D determinants, measured through an in-person interview, and serum 25(OH)D concentrations. A total of 200 controls participating in a population-based case-control study in Montreal, Canada, provided a blood specimen and completed an in-person interview on socio-demographic, reproductive, medical and lifestyle characteristics and personal attributes. Serum 25(OH)D concentrations were quantified by liquid chromatography-tandem MS. Multivariable least squares regression was used to build models that predict 25(OH)D concentrations from interview responses. We assessed high-order effects, performed sensitivity analysis using the lasso method and conducted cross-validation of the prediction models. Prediction models were built for users and non-users of vitamin D supplements separately. Among users, alcohol intake, outdoor time, sun protection, dose of supplement use, menopausal status and recent vacation were predictive of 25(OH)D concentrations. Among non-users, BMI, sun sensitivity, season and recent vacation were predictive of 25(OH)D concentrations. In cross-validation, 46-47 % of the variation in 25(OH)D concentrations were explained by these predictors. In the absence of 25(OH)D measures, our study supports that predicted 25(OH)D scores may be used to assign exposure in epidemiological studies that examine vitamin D exposure.

Ancestry-Adjusted Vitamin D Metabolite Concentrations in Association With Cytochrome P450 3A Polymorphisms

We investigated the association between genetic polymorphisms in cytochrome P450 (CYP2R1, CYP24A1, and the CYP3A family) with nonsummer plasma concentrations of vitamin D metabolites (25-hydroxyvitamin D3 (25(OH)D3) and proportion 24,25-dihydroxyvitamin D3 (24,25(OH)2D3)) among healthy individuals of sub-Saharan African and European ancestry, matched on age (within 5 years; n = 188 in each ancestral group), in central suburban Pennsylvania (2006-2009). Vitamin D metabolites were measured using high-performance liquid chromatography with tandem mass spectrometry. Paired multiple regression and adjusted least-squares mean analyses were used to test for associations between genotype and log-transformed metabolite concentrations, adjusted for age, sex, proportion of West-African genetic ancestry, body mass index, oral contraceptive (OC) use, tanning bed use, vitamin D intake, days from summer solstice, time of day of blood draw, and isoforms of the vitamin D receptor (VDR) and vitamin D binding protein. Polymorphisms in CYP2R1, CYP3A43, vitamin D binding protein, and genetic ancestry proportion remained associated with plasma 25(OH)D3 after adjustment. Only CYP3A43 and VDR polymorphisms were associated with proportion 24,25(OH)2D3. Magnitudes of association with 25(OH)D3 were similar for CYP3A43, tanning bed use, and OC use. Significant least-squares mean interactions (CYP2R1/OC use (P = 0.030) and CYP3A43/VDR (P = 0.013)) were identified. A CYP3A43 genotype, previously implicated in cancer, is strongly associated with biomarkers of vitamin D metabolism. Interactive associations should be further investigated.

Vitamin D and the Skin: An Update for Dermatologists

Vitamin D plays a key role in skeletal and cardiovascular disorders, cancers, central nervous system diseases, reproductive diseases, infections, and autoimmune and dermatological disorders. The two main sources of vitamin D are sun exposure and oral intake, including vitamin D supplementation and dietary intake. Multiple factors are linked to vitamin D status, such as Fitzpatrick skin type, sex, body mass index, physical activity, alcohol intake, and vitamin D receptor polymorphisms. Patients with photosensitive disorders tend to avoid sun exposure, and this practice, along with photoprotection, can put this category of patients at risk for vitamin D deficiency. Maintaining a vitamin D serum concentration within normal levels is warranted in atopic dermatitis, psoriasis, vitiligo, polymorphous light eruption, mycosis fungoides, alopecia areata, systemic lupus erythematosus, and melanoma patients. The potential determinants of vitamin D status, as well as the benefits and risks of vitamin D (with a special focus on the skin), will be discussed in this article.

Influent factors of gestational vitamin D deficiency and its relation to an increased risk of preterm delivery in Chinese population

Gestational vitamin D deficiency (VDD) has been linked with adverse pregnant outcomes. To investigate influent factors of gestational VDD and its relation to the incidence of preterm delivery, total 3598 eligible mother-and-singleton-offspring pairs were recruited. For serum 25(OH)D concentration, 941 pregnant women were sufficient, 1260 insufficient, and 1397 deficient. Further analysis showed that VDD was more prevalent in winter than in other seasons. Underweight but not overweight was a risk factor for gestational VDD. Multivitamin use reduced risk of gestational VDD. Interestingly, 8.23% delivered preterm infants among subjects with VDD (adjusted RR: 4.02; 95% CI: 2.33, 6.92) and 3.81% among subjects with gestational vitamin D insufficiency (VDI) (adjusted RR: 2.07; 95% CI: 1.16, 3.71). Moreover, 2.59% delivered early preterm infants among subjects with VDD (adjusted RR: 2.97; 95% CI: 1.41, 6.24) and 0.49% among subjects with VDI (adjusted RR: 0.54; 95% CI: 0.19, 1.51). The incidence of late preterm delivery was 5.64% among subjects with VDD (adjusted RR: 3.90; 95% CI: 2.26, 6.72) and 3.32% among subjects with VDI (adjusted RR: 2.09; 95% CI: 1.17, 3.74). In conclusion, pre-pregnancy BMI, seasonality and multivitamin use are influent factors of gestational vitamin D status. Gestational VDD is associated with an increased risk of preterm delivery in Chinese population.

Prevalence and Predictors of Low Serum 25-Hydroxyvitamin D among Female African-American Breast Cancer Survivors

BACKGROUND

African-American breast cancer survivors commonly demonstrate low serum 25-hydroxyvitamin D (25(OH)D). Decreased cutaneous conversion, high levels of adiposity, and even breast cancer treatment may influence vitamin D status. Previous investigations have analyzed African-American women in aggregate with other breast cancer survivors and have not comprehensively addressed these influential factors.

OBJECTIVES

To determine the prevalence of low serum 25(OH)D in an exclusively African-American cohort of female breast cancer survivors with overweight/obesity and to evaluate the role of ultraviolet (UV) light exposure, body composition, and dietary sources of vitamin D on serum 25(OH)D levels.

DESIGN

Cross-sectional.

PARTICIPANTS

Pre- and postmenopausal African-American breast cancer survivors (n=244) were recruited from various neighborhoods in the city of Chicago, IL, between September 2011 and September 2014 for a larger weight loss trial.

MAIN OUTCOME MEASURES

Demographic, clinical, anthropometric (body mass index [calculated as kg/m²], waist circumference, and hip circumference), blood specimen, dietary intake (food frequency questionnaire), and sun behavior data were collected by trained study personnel before trial participation. Dual-energy x-ray absorptiometry was used to quantify adiposity (total, percentage, regional, visceral) and lean mass. Serum 25(OH)D was used as the biomarker reflective of vitamin D status.

STATISTICAL ANALYSES

Mean (±standard deviation), frequencies, and multivariate linear regression modeling.

RESULTS

The average participant was 57.4 years old (±10.0), 6.9 years (±5.2) from initial breast cancer diagnosis with a body mass index of 36.2 (±6.2). The majority of participants (60%) reported habitual oral vitamin D supplementation with mean intake of 327 IU (±169). Vitamin D deficiency was prevalent in 81% and 43%, when the cut points of the Endocrine Society (<30 ng/mL or <75 nmol/L) and the Institute of Medicine (<20 ng/mL or <50 nmol/L) were applied, respectively. A multivariate model adjusting for age, seasonality of blood draw, total energy intake, use of supplemental vitamin D, darker skin pigmentation, breast cancer stage, and waist-to-hip ratio was able to explain 28.8% of the observed variance in serum 25(OH)D concentrations. No significant associations were detected for body mass index or any dual-energy x-ray absorptiometry measures of body composition.

CONCLUSIONS

Considering the number of women who endorsed use of vitamin D supplementation, the prevalence of vitamin D deficiency among these African-American breast cancer survivors was high. Vitamin D supplementation, sun behavior, and waist-to-hip ratio may serve as future points of intervention to improve the vitamin D status of this minority survivor population.

Prevalence and Predictors of Subclinical Micronutrient Deficiency in German Older Adults: Results from the Population-Based KORA-Age Study

Subclinical micronutrient deficiency in older adults is associated with chronic age-related diseases and adverse functional outcomes. In Germany, the older population is at risk of insufficient micronutrient intake, but representative studies on micronutrient status in old and very old adults are scarce. This study’s objectives were to estimate the prevalence of subclinical vitamin D, folate, vitamin B₁₂ and iron deficiencies among older adults, aged 65 to 93, from the KORA-Age study in Augsburg, Germany (n = 1079), and to examine associated predictors, using multiple logistic regression. Serum concentrations of 25-hydroxyvitamin D (25OHD), folate, vitamin B₁₂, and iron were analyzed. The prevalence of subclinical vitamin D and vitamin B₁₂ deficiencies were high, with 52.0% and 27.3% of individuals having low 25OHD (<50 nmol/L) and low vitamin B₁₂ concentrations (<221 pmol/L), respectively. Furthermore, 11.0% had low iron (men <11.6 µmol/L, women <9.0 µmol/L) and 8.7% had low folate levels (<13.6 nmol/L). Common predictors associated with subclinical micronutrient deficiency included very old age, physical inactivity, frailty and no/irregular use of supplements. Subclinical micronutrient deficiency is a public health concern among KORA-Age participants, especially for vitamins D and B₁₂. The predictors identified provide further rationale for screening high-risk subgroups and developing targeted public health interventions to tackle prevailing micronutrient inadequacies among older adults.

Function of the vitamin D endocrine system in mammary gland and breast cancer

The nuclear receptor for 1α,25-dihydroxycholecalciferol (1,25D), the active form of vitamin D, has anti-tumor actions in many tissues. The vitamin D receptor (VDR) is expressed in normal mammary gland and in many human breast cancers suggesting it may represent an important tumor suppressor gene in this tissue. When activated by 1,25D, VDR modulates multiple cellular pathways including those related to energy metabolism, terminal differentiation and inflammation. There is compelling pre-clinical evidence that alterations in vitamin D status affect breast cancer development and progression, while clinical and epidemiological data are suggestive but not entirely consistent. The demonstration that breast cells express CYP27B1 (which converts the precursor vitamin D metabolite 25D to the active metabolite 1,25D) and CYP24A1 (which degrades both 25D and 1,25D) provides insight into the difficulties inherent in using dietary vitamin D, sun exposure and/or serum biomarkers of vitamin D status to predict disease outcomes. Emerging evidence suggests that the normally tight balance between CYP27B1 and CYP24A1 becomes deregulated during cancer development, leading to abrogation of the tumor suppressive effects triggered by VDR. Research aimed at understanding the mechanisms that govern uptake, storage, metabolism and actions of vitamin D steroids in normal and neoplastic breast tissue remain an urgent priority.

Predictors and correlates of serum 25-hydroxyvitamin D concentrations in young women: results from the Safe-D study

Vitamin D deficiency is a global public health concern. Studies of serum 25-hydroxyvitamin D (25(OH)D) determinants in young women are limited and few include objective covariates. Our aims were to define the prevalence of vitamin D deficiency and examine serum 25(OH)D correlates in an exploratory study of women aged 16–25 years. We studied 348 healthy females living in Victoria, Australia, recruited through Facebook. Data collected included serum 25(OH)D assayed by liquid chromatography-tandem MS, relevant serum biochemistry, soft tissue composition by dual-energy X-ray absorptiometry, skin melanin density, Fitzpatrick skin type, sun exposure using UV dosimeters and lifestyle factors. Mean serum 25(OH)D was 68 (sd27) nmol/l and 26 % were vitamin D deficient (25(OH)D <50 nmol/l). The final model explained 56 % of 25(OH)D variance. Serum sex hormone-binding globulin levels, creatinine levels, sun exposure measured by UV dosimeters, a positive attitude towards sun tanning, typically spending >2 h in the sun in summer daily, holidaying in the most recent summer period, serum Fe levels, height and multivitamin use were positively associated with 25(OH)D. Fat mass and a blood draw in any season except summer was inversely associated with 25(OH)D. Vitamin D deficiency is common in young women. Factors such as hormonal contraception, sun exposure and sun-related attitudes, as well as dietary supplement use are essential to consider when assessing vitamin D status. Further investigation into methods to safely optimise vitamin D status and to improve understanding of the impact of vitamin D status on long-term health outcomes is required.

Vitamin D status and associated factors among Portuguese older adults: results from the Nutrition UP 65 cross-sectional study

OBJECTIVES

To evaluate vitamin D status and its associated factors in Portuguese older adults from the Nutrition UP 65 study.

DESIGN

Cross-sectional observational study.

PARTICIPANTS AND METHODS

Nationwide cluster sample of 1500 Portuguese subjects ≥65 years old. Participants were classified, according to US Institute of Medicine cut-offs, as presenting normal 25-hydroxyvitamin D (25(OH)D) levels (≥50.0 nmol/L), at risk of inadequacy (30.0-49.9 nmol/L) or at risk of deficiency (<30 nmol/L). The association between individuals' characteristics and 25(OH)D levels was analysed through multinomial logistic regression analysis.

RESULTS

Median 25(OH)D serum value was 36.1 (interquartile range (IQR): 35.5) nmol/L. According to the used cut-offs, 39.6% of participants were at risk of 25(OH)D deficiency and 29.4% were at risk of 25(OH)D inadequacy. In the adjusted model, having higher skin pigmentation and waist circumference >88 cm for women and >102 cm for men were associated with higher odds of 25(OH)D deficiency. Otherwise, living in Lisbon Metropolitan Area and in Madeira, 1-12 years of schooling, being married or in a common-law marriage, monthly income ≥€1000, alcohol consumption, medication or supplements with vitamin D supplement use, and blood samples collected in spring or summer were associated with lower odds of being at risk of 25(OH)D deficiency. In this model, season of blood sample collection, medication or supplements use, and waist circumference were the factors more strongly associated with 25(OH)D levels.

CONCLUSIONS

Despite using the conservative Institute of Medicine cut-offs, over two-thirds of these study participants presented inadequate 25(OH)D levels, warranting the implementation of corrective measures. Potentially modifiable factors were strongly associated with 25(OH)D levels in this study. These findings may be particularly relevant to the development of public health policies in southern European countries.

Serum Parathyroid Hormone Responses to Vitamin D Supplementation in Overweight/Obese Adults: A Systematic Review and Meta-Analysis of Randomized Clinical Trials

Obesity is often associated with vitamin D deficiency and secondary hyperparathyroidism. Vitamin D supplementation typically leads to the reductions in serum parathyroid hormone (PTH) levels, as shown in normal weight individuals. Meanwhile, the dose of vitamin D supplementation for the suppression of PTH may differ in overweight and obese adults. We conducted a systematic review and meta-analysis of randomized controlled trials to determine the dose of vitamin D supplementation required to suppress PTH levels in overweight/obese individuals. We identified 18 studies that examined overweight or obese healthy adults who were supplemented with varying doses of vitamin D3. The primary outcomes examined were changes in PTH and serum 25-hydroxyvitamin D (25OHD) levels from baseline to post-treatment. The results of the meta-analysis showed that there was a significant treatment effect of vitamin D supplementation on PTH, total standardized mean difference (SMD) (random effects) = -0.38 (95% CI = -0.56 to -0.20), t = -4.08, p < 0.001. A significant treatment effect of vitamin D supplementation was also found on 25OHD, total SMD (random effects) = 2.27 (95% CI = 1.48 to 3.06) t = 5.62, p < 0.001. Data from available clinical trials that supplemented adults with D3 ranging from 400 IU to 5714 IU, showed that 1000 IU of vitamin D supplementation best suppressed serum PTH levels, total SMD = -0.58, while vitamin D supplementation with 4000 IU showed the greatest increase in serum 25OH levels. Vitamin D and calcium supplementation of 700 IU and 500 mg, respectively, also showed a significant treatment effect on the suppression of PTH with a total SMD = -5.30 (95% CI = -9.72 to -0.88). In conclusion, the meta analysis of available clinical trials indicates that 1000 IU vitamin D supplementation can suppress serum PTH levels, while 4000 IU of vitamin D was associated with the largest increase in serum 25OHD levels in the overweight and obese population.

Lifestyle and Other Factors Explain One-Half of the Variability in the Serum 25-Hydroxyvitamin D Response to Cholecalciferol Supplementation in Healthy Adults

BACKGROUND

Many factors have been associated with serum 25-hydroxyvitamin D [25(OH)D] concentrations in observational studies, with variable consistency. However, less information is available on factors affecting the magnitude of changes in serum 25(OH)D resulting from vitamin D supplementation.

OBJECTIVE

This study aimed to identify factors associated with the serum 25(OH)D response to supplementation with 1000 IU cholecalciferol/d during the first year of a large, multicenter, randomized, placebo-controlled colorectal adenoma chemoprevention trial.

METHODS

Eligible older adults who were not vitamin D-deficient [serum 25(OH)D ≥12 ng/mL] were randomly assigned in a modified 2 × 2 factorial design to 1 of 4 groups: daily 1000 IU cholecalciferol, 1200 mg Ca as carbonate, both, or placebo. Women could elect 2-group (calcium ± cholecalciferol) random assignment. In secondary analyses, we used multivariable models to assess factors associated with serum 25(OH)D concentrations in all enrollees (n = 2753) and with relative changes in serum 25(OH)D after 1 y cholecalciferol supplementation among those randomly assigned (n = 2187).

RESULTS

In multivariable models, 8 factors accounted for 50% of the variability of proportional change in serum 25(OH)D after cholecalciferol supplementation. Larger increases were associated with being female (34.5% compared with 20.5%; P < 0.001) and with lower baseline serum 25(OH)D (P < 0.0001), optimal adherence to study pill intake (P = 0.0002), wearing long pants and sleeves during sun exposure (P = 0.0002), moderate activity level (P = 0.01), use of extra vitamin D-containing supplements during the trial (P = 0.03), and seasons of blood draw (P ≤ 0.002). Several genetic polymorphisms were associated with baseline serum 25(OH)D and/or serum response, but these did not substantially increase the models' R² values. Other factors, including body mass index, were associated with serum 25(OH)D at baseline but not with its response to supplemental cholecalciferol.

CONCLUSIONS

The factors that most affected changes in serum 25(OH)D concentrations in response to cholecalciferol supplementation included sex, baseline serum 25(OH)D, supplement intake adherence, skin-covering clothes, physical activity, and season. Genetic factors did not play a major role. This trial was registered at www.clinicaltrials.gov as NCT00153816.

Circulating 25-hydroxyvitamin D and physical performance in older adults: a nationwide study in Taiwan

BACKGROUND

A previous study indicated that 31% of the elderly in Taiwan have a vitamin D deficiency. Vitamin D adequacy has been associated with physical performance in the elderly.

OBJECTIVES

The first aim of the current study was to identify the determinants for vitamin D deficiency. The second aim was to evaluate the association between vitamin D status and physical performance.

DESIGN

A total of 5664 community-dwelling participants aged ≥55 y were recruited since 2008. Plasma total 25-hydroxyvitamin D concentrations were originally determined by ELISA and calibrated to a chemiluminescence measurement. Physical performance was assessed by handgrip strength, the Short Physical Performance Battery, timed up and go, a 6-min walk test, and single-leg stands. Multiple linear regression and logistic regression were used to estimate the cross-sectional associations.

RESULTS

Vitamin D inadequacy (<50 nmol/L) was related to higher education (P-trend < 0.01), body mass index [(BMI; in kg/m²) ORs (95% CIs) for ≥30 compared with 18.5 to <25 were 1.78 (1.14, 2.78) for men and 1.53 (1.11, 2.11) for women], and vegetable intake [fourth compared with first quartile, 1.58 (1.15, 2.18) for men and 2.38 (1.82, 3.12) for women]. Higher intakes of fish [fourth compared with first quartile, 0.44 (0.33, 0.59) for men and 0.27 (0.21, 0.36) for women] and milk [fourth compared with first quartile, 0.46 (0.31, 0.69) for men and 0.69 (0.49, 0.95) for women] were associated with lower risk of vitamin D inadequacy. Few subjects had 25-hydroxyvitamin D concentrations <30 nmol/L. Above that concentration, there was no dose-effect relation with physical performance except for single-leg stands.

CONCLUSIONS

The factors associated with vitamin D inadequacy in Taiwan were higher education, higher BMI, and lower fish and milk intakes. No dose-effect relation existed between vitamin D concentration and physical performance except for single-leg stands. This study was registered at www.clinicaltrials.gov as NCT02677831.

The association between Vitamin D and health outcomes in women: A review on the related evidence

BACKGROUND

Vitamin D has a wide range of physiological functions in skeletal and nonskeletal tissues which may play a role in many diseases. The aim of this study was to evaluate the recent evidence regarding the effects of Vitamin D on several health outcomes in women including breast cancer, ovarian and endometrial cancers, hypertension, and osteoporosis.

MATERIALS AND METHODS

We searched PubMed and Google Scholar databases through March 2016. We included the most current systematic reviews and meta-analyses assessing the associations of Vitamin D intake and/or serum 25-hydroxyvitamin D (25(OH)D) levels with the risk of incidence of breast cancer, ovarian and endometrial cancers, hypertension, and osteoporosis.

RESULTS

Many studies have represented that Vitamin D supplementation and high 25(OH)D levels can decrease the risk of breast cancer occurrence or mortality. However, there is no strong evidence to support the existence of a relationship between Vitamin D and ovarian or endometrial cancers. Furthermore, the results regarding the effects of Vitamin D on hypertension were inconsistent. Although observational studies have shown an association between Vitamin D and hypertension, there is no evidence regarding effectiveness of Vitamin D in lowering blood pressure in several clinical trials. On the other hand, the findings associating the impact of Vitamin D on osteoporosis were more definitive and most studies have represented that Vitamin D may have beneficial effects on osteoporosis.

CONCLUSION

Although the adequate Vitamin D level can play a protective role in the incidence and development of breast cancer, hypertension, and osteoporosis, there is limited evidence regarding ovarian and endometrial cancers.

Vitamin D Status and Risk of Breast Cancer in Iranian Women: A Case-Control Study

OBJECTIVE

Considering the rising incidence of breast cancer and high prevalence of vitamin D deficiency in Iran, this case-control study aimed to investigate the relationship between serum concentration and intake of vitamin D and risk of breast cancer.

METHODS

A total of 135 incident breast cancer cases at the Cancer Research Center of Shahid Beheshti University of Medical Sciences were matched with 135 controls by age and menopausal status. A validated and reliable 168-item food frequency questionnaire was completed by participant interviews. To determine the vitamin D content of foods we used the U.S. Department of Agriculture (USDA) nutrient database. To analyze the food frequency questionnaires we used the data collected in the Iranian Household Food Pattern Study, conducted by the National Nutrition and Food Technology Research Institute and the Iranian Ministry of Agriculture. Five-milliliter blood samples were collected to measure serum 25-hydroxyvitamin D (25(OH)D) using an enzyme-linked immunosorbent assay method.

RESULTS

Women in the fourth quartile of serum 25(OH)D level had 3 times lower risk of developing breast cancer compared to those in the first quartile. In the adjusted model the inverse relationship remained significant (odds ratio [OR] = 0.269; 95% confidence interval [CI], 0.122-0.593). In the stratified model by menopausal status the inverse association was only seen in premenopausal women (OR = 0.25; 95% CI, 0.094-0.687). Dietary intake of vitamin D was inversely associated with risk of breast cancer (OR fourth quartile [Q4] vs first quartile [Q1] = 0.39; 95% CI, 0.196-0.784; p = 0.008). After adjusting for the confounding factors, this inverse association remained significant.

CONCLUSION

Results from this case-control study support the protective effect of higher serum concentration of 25(OH)D against breast cancer. Moreover, dietary but not total intake of vitamin D was associated with decreased risk of breast cancer.

The cross-sectional relationships of dietary and serum vitamin D with cardiometabolic risk factors: Metabolic components, subclinical atherosclerosis, and arterial stiffness

OBJECTIVE

There has been increasing interest in non-skeletal interactions between vitamin D insufficiency, which is common, and cardiovascular event and cardiovascular disease (CVD) risk factors.

METHODS

To evaluate cross-sectional associations between dietary and serum vitamin D status and metabolic abnormalities and arterial changes among 1054 adults aged ≥40 y (404 men and 650 women) in a rural area of South Korea. Study subjects were divided into three groups according to dietary vitamin D intake (tertiles) measured by food frequency questionnaire and serum 25(OH)D levels (≤20, 21-29, and ≥30 ng/mL). Metabolic components (blood pressure, lipid profiles, and glycemic index) and arterial changes (brachial ankle pulse wave velocity [baPWV] and carotid artery intima-media wall thickness [cIMT]) were measured.

RESULTS

Dietary vitamin D was inversely associated with diastolic blood pressure (DBP) and baPWV among men, but the association disappeared after multinutrient supplement users were excluded. Among women, there was an inverse association between dietary vitamin D and triacylglycerol (TG) levels. However, serum 25(OH)D showed a significant positive relationship with HDL cholesterol in both men and women, while a positive linear trend or nonlinear trend with serum 25(OH)D levels was shown in TG levels among men and in systolic blood pressure (SBP), DBP, total cholesterol, and baPWV among women. The positive relationship between serum 25(OH)D with baPWV disappeared after adjustment for blood pressure.

CONCLUSIONS

Serum 25(OH)D may be favorably related to HDL cholesterol. However, serum 25(OH)D may not favorably related to subclinical atherosclerosis and arterial stiffness measured by cIMT and baPWV. The positive relationship between 25(OH)D and baPWV is likely to be mediated by blood pressure.

Are the current Australian sun exposure guidelines effective in maintaining adequate levels of 25-hydroxyvitamin D?

An adequate vitamin D status, as measured by serum 25-hydroxyvitamin D (25(OH)D) concentration, is important in humans for maintenance of healthy bones and muscle function. Serum 25(OH)D concentration was assessed in participants from Melbourne, Australia (37.81S, 144.96E), who were provided with the current Australian guidelines on sun exposure for 25(OH)D adequacy (25(OH)D ≥50 nmol/L). Participants were interviewed in February (summer, n=104) and August (winter, n=99) of 2013. Serum 25(OH)D concentration was examined as a function of measures of sun exposure and sun protection habits with control of key characteristics such as dietary intake of vitamin D, body mass index (BMI) and skin colour, that may modify this relationship. The mean 25(OH)D concentration in participants who complied with the current sun exposure guidelines was 67.3 nmol/L in summer and 41.9 nmol/L in winter. At the end of the study, 69.3% of participants who complied with the summer sun exposure guidelines were 25(OH)D adequate, while only 27.6% of participants who complied with the winter sun exposure guidelines were 25(OH)D adequate at the end of the study. The results suggest that the current Australian guidelines for sun exposure for 25(OH)D adequacy are effective for most in summer and ineffective for most in winter. This article is part of a Special Issue entitled '17th Vitamin D Workshop'.

Effect of combined oral contraceptive use on serum 25-hydroxy vitamin D levels and ultrasound parameters in patients with polycystic ovary syndrome

PURPOSE

To investigate if there is an effect of combined oral contraceptive (COC) use on serum 25-hydroxy vitamin D [25(OH)D] levels in patients with polycystic ovary syndrome (PCOS).

METHODS

PCOS was defined by the 2003 Rotterdam criteria. All patients with PCOS were treated with a COC containing 0.035 mg ethinylestradiol and 2 mg cyproterone acetate for 6 months. Serum 25(OH)D levels, HOMA-IR, ovarian volume and antral follicule count were measured before and after the treatment.

RESULTS

The median 25(OH)D levels were 9.40 (range 4.40-24.50) μg/l and 7.00 (5.00-13.50) μg/l before and after COC use, respectively. Serum 25(OH)D levels decreased after the treatment; however, the difference was not statistically significant (p = 0.055).

CONCLUSION

This study seems to be the first prospective trial revealing the effect of COC use on serum 25(OH)D levels in women with PCOS. Although the decrease in serum 25(OH)D levels in patients with PCOS with the use of COC alone, did not reach to statistically significance level after 6 months treatment with COC.

Vitamin D status among adults in Germany--results from the German Health Interview and Examination Survey for Adults (DEGS1)

Background

In 1998, more than half of the adult population in Germany had serum 25-hydroxy-vitamin-D [25(OH)D] levels below the common threshold of 50 nmol/l. Since then, there has been a lot of attention for vitamin D in the scientific community, the media and the general population and serum 25(OH)D levels may have increased as a consequence. With data from the ‘German Health Interview and Examination Survey for Adults’ (DEGS1) the current situation of vitamin D status can be analysed.

Methods

DEGS1, a national health survey among adults in Germany conducted by the Robert Koch Institute between 2008 and 2011, included 6,995 persons with available serum 25(OH)D levels. We calculated the proportion of participants with serum 25(OH)D levels <30 nmol/l, 30- < 50 nmol/l and > =50 nmol/l overall and according to age, season and latitude of residence as well as percentiles of serum 25(OH)D according to month of examination. Determinants of vitamin D status were analysed with multiple linear regression models.

Results

Mean serum 25(OH)D level was 45.6 nmol/l with no significant sex differences (p = 0.47). 61.6 % of the participants had serum 25(OH)D levels <50 nmol/l, 30.2 % had levels <30 nmol/l. During summer, half of the participants had levels > =50 nmol/l, during winter time, 25 % of the participants had levels <30 nmol/l. A significant latitudinal gradient was observed in autumn for men and in winter for women.

In multiple linear regression analyses, examination during winter time, residing in northern latitude, non-use of vitamin D supplements, low sport activity, high Body Mass Index (BMI) and high media consumption were independently and significantly associated with lower serum 25(OH)D levels in both sexes. In addition, among women, significant associations with lower 25(OH)D levels were observed for older age and lower socio-economic status, among men, for low vitamin D intake and more residential traffic.

Conclusions

Serum 25(OH)D levels below the threshold of 50 nmol/l are still common among adults in Germany, especially during winter and spring and in higher latitudes. Potentially modifiable factors of poorer vitamin D status are higher BMI, lack of sport activity and high media use.

Clinical implications of vitamin D deficiency

Vitamin D deficiency is a common medical problem worldwide and its prevalence rises along with latitude, obesity, sedentary lifestyle, limited sunlight exposure and aging. A great body of evidence has shown that patients with vitamin D deficiency have increased cardiovascular risks and total mortality. Conversely, the presence of comorbidities progressive with age such as abdominal obesity, insulin resistance, type 2 diabetes and hypertension places the patients at an increased risk of vitamin D deficiency. The multidirectional effect of vitamin D deficiency is present in different phases of the aging process. Based on the literature review, the risk factors for vitamin D insufficiency most often found in post-menopausal women include limited sun exposure and time spent outdoors, inadequate dietary vitamin D intake, winter season and increased age. Vitamin D supplementation in this group might offer prevention of falls and fractures and may be beneficial for cardiovascular health, what may be especially important in osteoporotic and elderly populations. Prevention and treatment processes involve education regarding sunlight exposure and pharmacological cholecalciferol supplementation according to the recommendations for Central Europe. This manuscript reviews the role of vitamin D and its deficiency and considers their clinical implications, with particular regard to peri- and postmenopausal women.

Adequate vitamin D levels in a Swedish population living above latitude 63°N: The 2009 Northern Sweden MONICA study

Background

Even though vitamin D is mainly produced by exposure to sunlight, little is known regarding vitamin D levels in populations living in sub-Arctic areas with little or no daylight during winter.

Objective

We describe distributions of vitamin D3 and the prevalence of adequate levels in a population living above 63°N.

Design

We sampled 1,622 randomly selected subjects, aged 25–74 years, between January and May, 2009, as part of the Northern Sweden MONICA study (69.2% participation rate). By using HPLC, 25(OH) vitamin D3 was analysed. Levels used for definitions were deficient, D3<25 nmol/l (<10 ng/ml); insufficient, D3 25–49.9 nmol/l (10–20 ng/ml); and adequate, D3≥50 nmol/l (20 ng/ml).

Results

Mean (median) level of vitamin D3 was 65.2 (63.6) nmol/l in men and 71.0 (67.7) nmol/l in women. Adequate levels were found in 79.2%, more often in women (82.7%) than in men (75.6%). Only 0.7% of the population were vitamin D3–deficient but 23.1% of men and 17.1% of women had insufficient levels. Levels of vitamin D3 increased with age and insufficient status was most common among those aged 25–34 years, 41.0% in men and 22.3% in women.

If subjects using vitamin D-supplementation are excluded, the population level of D3 is 1–2 nmol/l lower than in the general population across sex- and age groups. There were no differences between the northern or the southern parts, between urban or rural living or according to educational attainment. Those subjects born outside of Sweden or Finland had lower levels.

Conclusion

The large majority living close to the Arctic Circle in Sweden have adequate D3 levels even during the second half of the dark winter. Subjects with D3 deficiency were uncommon but insufficient levels were often found among young men.

Vitamin D status is inversely associated with obesity in a clinic-based sample in Puerto Rico

Studies show that vitamin D status is associated to obesity but data in Hispanic individuals is scarce. The aim of this study was to assess the association between vitamin D status and obesity in a clinic-based sample in Puerto Rico. We hypothesized that subjects with a higher adiposity would have a lower vitamin D status. We extracted the following data from medical records of a private clinic: age, gender, serum 25(OH)D levels, weight, height, and waist circumference. Body mass index (BMI) (kg/m(2)) and waist-to-height ratio were calculated and categorized according to standard guidelines. Statistical analyses included analysis of covariance, Pearson correlations and χ(2) test. From 797 individuals (mean age 53.7 ± 15.4 years; 63.5% females), 35.6% were overweight and 43.7% obese. Mean 25(OH)D levels were 24.7 ± 8.7 ng/mL; 5.3% had levels <12 ng/mL, 30.6% had levels 12 to 20 ng/mL, and 43.5% had levels 21 to 30 ng/mL. Mean 25(OH)D levels were significantly higher in normal weight and overweight males compared to obese males (P < .05) and in overweight females compared to obese females (P < .05). Levels were also higher in those with low risk compared to high risk of waist circumference and waist-to-height ratio (P < .001). BMI, waist circumference, and waist-to-height ratio were inversely correlated to 25(OH)D levels (P < .001). A greater proportion of obese individuals (41.4%) were vitamin D deficient or insufficient compared to the normal weight (33.9%) and overweight individuals (30.3%) (P < .05). In conclusion, in this clinic-based sample of Puerto Rican adults, those with higher BMI, waist circumference, and waist-to-height ratio had a significantly lower vitamin D status.

Suicidal patients are deficient in vitamin D, associated with a pro-inflammatory status in the blood

BACKGROUND

Low levels of vitamin D may play a role in psychiatric disorders, as cross-sectional studies show an association between vitamin D deficiency and depression, schizophrenia and psychotic symptoms. The underlying mechanisms are not well understood, although vitamin D is known to influence the immune system to promote a T helper (Th)-2 phenotype. At the same time, increased inflammation might be of importance in the pathophysiology of depression and suicide. We therefore hypothesized that suicidal patients would be deficient in vitamin D, which could be responsible for the inflammatory changes observed in these patients.

METHODS

We compared vitamin D levels in suicide attempters (n=59), non-suicidal depressed patients (n=17) and healthy controls (n=14). Subjects were diagnosed according to the Diagnostic and Statistical Manual of Mental Disorders, 4th edition, and went through a structured interview by a specialist in psychiatry. 25(OH)D2 and 25(OH)D3 were measured in plasma using liquid-chromatography-mass-spectrometry (LC-MS). We further explored vitamin D's association with plasma IL-1β, IL-6 and TNF-α.

RESULTS

Suicide attempters had significantly lower mean levels of vitamin D than depressed non-suicidal patients and healthy controls. 58 percent of the suicide attempters were vitamin D deficient according to clinical standard. Moreover, there was a significant negative association between vitamin D and pro-inflammatory cytokines in the psychiatric patients. Low vitamin D levels were associated with higher levels of the inflammatory cytokines IL-6 and IL-1β in the blood.

CONCLUSION

The suicide attempters in our study were deficient in vitamin D. Our data also suggest that vitamin D deficiency could be a contributing factor to the elevated pro-inflammatory cytokines previously reported in suicidal patients. We propose that routine clinical testing of vitamin D levels could be beneficial in patients with suicidal symptoms, with subsequent supplementation in patients found to be deficient.

Determinants of vitamin D status in Caucasian adults: influence of sun exposure, dietary intake, sociodemographic, lifestyle, anthropometric, and genetic factors

Very few studies have investigated the determinants of serum vitamin D levels using a set of variables that include simultaneously sun exposure, phototype, dietary intake, sociodemographics, anthropometric, lifestyle data, and genetic polymorphisms. Our objective was to investigate the associations between all these parameters and vitamin D status in a large sample of French adults. This cross-sectional survey was based on 1,828 middle-aged Caucasian adults from the SU.VI.MAX (SUpplémentation en VItamines et Minéraux AntioXydants) study. Plasma 25-hydroxyvitamin D (25OHD) concentration was lower among women (P<0.0001), older subjects (P=0.04), obese/underweight (P<0.0001), those living at higher latitudes (P<0.0001), those whose blood draw occurred in early spring (P<0.0001), less physically active (P<0.0001), with low sun exposure (P<0.0001), and with no-to-low alcohol intake (P=0.0001). Mutant GC rs4588 and rs7041 single nucleotide polymorphisms were associated with lower and higher 25OHD concentrations, respectively (P<0.0001). Dietary intake was not a major determinant of vitamin D status (P=0.7). This study provides an overall picture of determinants of vitamin D status. Several modifiable factors were identified, such as daily-life moderate sun exposure, physical activity, and normal-weight maintenance, which should be targeted by public health policies in order to improve vitamin D status in the general population, while avoiding active/intensive sun exposure, in line with recommendations for skin cancer prevention.

Winter 25-hydroxyvitamin D levels in young urban adults are affected by smoking, body mass index and educational level

BACKGROUND/OBJECTIVES

To study the relationship of winter 25-hydroxycholecalciferol (25-OHD) levels with age, education, place of residency, marital status and body mass index (BMI) as they may affect sun exposure, vitamin D synthesis and metabolism.

SUBJECTS/METHODS

Subjects (1952) answered a structured questionnaire concerning education, marital status and smoking; and body weight/height, and parathyroid hormone and 25-OHD were measured.

RESULTS

25-OHD levels were higher in the males with elementary and secondary education compared with higher education (46.8±18.5 and 43.7±16 vs 39.9±15.3 nmol/l, P<0.01). Vitamin D deficiency was more prevalent (16.7%, (13.1-20.2) vs 10.8%, (8.4-13.2), P=0.08) and sufficiency was less prevalent (24.6% (20-29.2) vs 33.7%, (29.5-37.8), P=0.005) in those with higher than secondary education. No differences were found among the females. Male smokers had lower 25-OHD than nonsmokers (40.2±16.6 vs 43.6±15.7 nmol/l, P=0.004). Deficiency was more prevalent in the male smokers than nonsmokers with secondary and higher education (secondary 16.6%, (10.1-22.4) vs 8.2%, (5.1-11.3), P=0.006; higher 27.4%, (17.7-37.1) vs 13.2%, (9.0-17.5), P=0.003). 25-OHD was lower in the obese than in the normal-weight females (34.6±16.2 vs 38.2±17.8 nmol/l, analysis of variance, P=0.014), but not males. Marital status was not related to 25-OHD. Only in the urban residents, increasing BMI in the young females increased the risk for vitamin D deficiency by 1%, and smoking had an odds ratio of 1.99 (1.05-3.78) in the young and 2.5 (1.07-5.75) in the middle-aged males.

CONCLUSIONS

Smoking and higher education in the males and obesity in the females were factors for vitamin D deficiency among Bulgarian urban population.

Vitamin D intake determines vitamin d status of postmenopausal women, particularly those with limited sun exposure

Few detailed data are available on the wide range of determinants of vitamin D status among postmenopausal women, and it is also unclear whether there may be undiscovered determinants. The objective of this study was to comprehensively evaluate determinants of serum 25-hydroxyvitamin D [25(OH)D] concentrations in a large cohort of postmenopausal women. Data from a subset of the Women's Health Initiative Observational Study were analyzed (50-79 y; n = 3345). Information on diet, lifestyle behaviors, secondhand smoke, use of dietary supplements and medication, chronic diseases, and anthropometry was collected at baseline (1993-1998) and on sun exposure at year 4 follow-up. Linear regression was performed to estimate regression coefficients (β). Significant determinants were total vitamin D intake (food plus supplements per 100 IU/d, β = 2.08), years of supplemental vitamin D use (β = 0.15), total fat intake (grams per day, β = -0.03), smoking status (β = -2.64, current vs. never), regional solar irradiance (β = 6.26, 475-500 vs. 300-325 Langleys), daylight time spent outdoors in summer (β = 5.15, >2 h vs. <30 min/d), recreational physical activity (metabolic equivalent task per hour per week, β = 0.13), waist circumference (centimeters, β = -0.26), and race/ethnicity (β = -11.94, black vs. white). Total vitamin D intake (partial R(2) = 0.09) explained the most variance in serum 25(OH)D concentrations (total R(2) = 0.29). The association between total vitamin D intake and serum 25(OH)D concentrations was stronger among participants who spent less rather than more daylight time outdoors in summer (P-interaction = 0.026). History and medications for hypertension, hyperlipidemia, and type 2 diabetes and secondhand smoke exposure were not associated with serum 25(OH)D. In conclusion, dietary factors and sun exposure remain important determinants of vitamin D status in postmenopausal women. Vitamin D intake should be emphasized for those with limited sun exposure.

Peroxisome proliferator-activated receptor and vitamin d receptor signaling pathways in cancer cells

Peroxisome proliferator-activated receptors (PPARs) are members of the superfamily of nuclear hormone receptors, which respond to specific ligands such as polyunsaturated fatty acids by altering gene expression. Three subtypes of this receptor have been discovered, each evolving to achieve different biological functions. Like other nuclear receptors, the transcriptional activity of PPARs is affected not only by ligand-stimulation, but also by cross-talk with other molecules. For example, both PPARs and the RXRs are ligand-activated transcription factors that coordinately regulate gene expression. In addition, PPARs and vitamin D receptor (VDR) signaling pathways regulate a multitude of genes that are of importance for cellular functions including cell proliferation and cell differentiation. Interaction of the PPARs and VDR signaling pathways has been shown at the level of molecular cross-regulation of their transcription factor. A variety of ligands influencing the PPARs and VDR signaling pathways have been shown to reveal chemopreventive potential by mediating tumor suppressive activities in human cancers. Use of these compounds may represent a potential novel strategy to prevent cancers. This review summarizes the roles of the PPARs and the VDR in pathogenesis and progression of cancer.