Plasma 25-hydroxyvitamin D3 and its relation to physical activity and other heart disease risk factors in the general population

The Importance of Vitamin D and Magnesium in Athletes

Vitamin D and magnesium are essential nutrients that play key roles in an athlete's performance, recovery, and overall health. Vitamin D is crucial for bone health (aiding calcium absorption and preventing stress fractures), muscle function (preventing weakness and injury), and reducing respiratory infections. Magnesium is fundamental in muscle function, adenosine triphosphate production for muscle contraction, electrolyte balance, bone strength, and cardiovascular health. The magnesium requirement of healthy adults is estimated at 300-400 mg/day, but there is evidence that athletes may have higher magnesium needs compared to sedentary persons. Magnesium and vitamin D are closely linked-vitamin D aids magnesium absorption, while magnesium is vital for vitamin D synthesis, transport, and activation. Given their importance in athletes, this article explores their functions, interactions, and the effects of deficiencies and supplementation in athletic populations.

Assessment of Vitamin D Status in the Drâa-Tafilalet Population (Morocco) Based on Sociodemographic, Health, and Nutritional Factors

The purpose of this study was to evaluate the vitamin D status and determine the factors influencing it in the Drâa-Tafilalet community (southeastern Morocco). Sociodemographic factors, health, cognitive status, sun exposure, and nutritional conditions were examined to help us understand their association with vitamin D status. Vitamin D data were gathered through laboratory testing, while demographic and health information was collected through interviews with participants in 2023. The study involved 100 participants aged 60 and above, most of whom were women (85%) rather than men (15%). The majority of participants were Arabs (90%), with a minority being Amazigh (10%). The average vitamin D level was 31.83 ± 10.55 ng/mL, varying based on participants' age, education, and gender. Sun-exposed individuals exhibited significantly higher mean vitamin D levels (33.56 ± 11.99 ng/mL) compared to those with limited sun exposure (28.97 ± 9.28 ng/mL). Moreover, the time spent outdoors, seasonal changes, and the duration of sun exposure affected the levels of vitamin D. These findings depict the vitamin D status of the elderly population of Drâa-Tafilalet, recognized as one of Morocco's poorest regions, shedding light on the significant influencers. Nonetheless, additional research is necessary to explore the correlation between dietary habits, sunlight exposure, and vitamin D levels in both young and elderly populations.

The effect of physical activity on vitamin D: A systematic review and meta-analysis of intervention studies in humans

Objectives

Cross-sectional studies demonstrate a positive association between higher physical activity and serum 25-hydroxyvitamin D (25(OH)D) concentration. However, whether this association is causal is unclear. We conducted a systematic review to identify intervention studies that examined the effect of physical activity on serum 25(OH)D concentration in humans.

Study design

Systematic review and meta-analysis.

Methods

We searched PubMed, Scopus and Web of Science to identify full-text peer-reviewed articles published in English from inception until January 2023. Eligible studies were randomised controlled trials or quasi-experimental studies. We used random effects meta-analysis to calculate the weighted mean difference (WMD) in the change in 25(OH)D concentration between physical activity and control groups. We used the revised Cochrane risk-of-bias tool for randomized trials (RoB 2) to assess the methodological quality of included studies.

Results

We included 32 articles in the systematic review and 24 in the meta-analysis. The intervention varied from resistance and weight-bearing exercises (n = 13) to aerobic exercises (n = 10), moderate and moderate-to-vigorous exercises (n = 5), aquatic exercise (n = 2), and multicomponent traditional exercises (n = 2) (Tai Chi and Yijinjing). The WMD in 25(OH)D in the physical activity and control groups was 9.51 and 4.87, respectively (between-group mean difference 4.64, p = 0.002). However, the difference was only evident in studies that implemented the intervention outdoors (n = 3; between-group mean difference 17.33, p < 0.0001); when the intervention was indoors there was no significant effect of physical activity on 25(OH)D (n = 16; between-group mean difference 1.80, p = 0.113).

Conclusions

This meta-analysis of physical activity interventions in humans showed that physical activity does not lead to increased 25(OH)D independently of time outdoors. However, most studies were under-powered, in many the exercise was low intensity, and vitamin D was not the primary outcome.

Vitamin D in Cancer Prevention: Gaps in Current Knowledge and Room for Hope

Intensive epigenome and transcriptome analyses have unveiled numerous biological mechanisms, including the regulation of cell differentiation, proliferation, and induced apoptosis in neoplastic cells, as well as the modulation of the antineoplastic action of the immune system, which plausibly explains the observed population-based relationship between low vitamin D status and increased cancer risk. However, large randomized clinical trials involving cholecalciferol supplementation have so far failed to show the potential of such interventions in cancer prevention. In this article, we attempt to reconcile the supposed contradiction of these findings by undertaking a thorough review of the literature, including an assessment of the limitations in the design, conduct, and analysis of the studies conducted thus far. We examine the long-standing dilemma of whether the beneficial effects of vitamin D levels increase significantly above a critical threshold or if the conjecture is valid that an increase in available cholecalciferol translates directly into an increase in calcitriol activity. In addition, we try to shed light on the high interindividual epigenetic and transcriptomic variability in response to cholecalciferol supplementation. Moreover, we critically review the standards of interpretation of the available study results and propose criteria that could allow us to reach sound conclusions in this field. Finally, we advocate for options tailored to individual vitamin D needs, combined with a comprehensive intervention that favors prevention through a healthy environment and responsible health behaviors.

Exercise: A Possibly Effective Way to Improve Vitamin D Nutritional Status

Vitamin D deficiency has become a widespread public health problem owing to its potential adverse health effects. Generally, the nutritional status of vitamin D depends on sunlight exposure and dietary or supplementary intake. However, recent studies have found that exercise can influence circulating 25(OH)D levels; although, the results have been inconclusive. In this review, we focused on the effect of exercise on circulating vitamin D metabolites and their possible mechanisms. We found that endurance exercise can significantly increase serum 25(OH)D levels in vitamin D-deficient people but has no significant effect on vitamin D-sufficient people. This benefit has not been observed with resistance training. Only chronic endurance exercise training can significantly increase serum 1,25(OH)₂D, and the effect may be sex-dependent. Exercise may influence 25(OH)D levels in the circulation by regulating either the vitamin D metabolites stored in tissues or the utilization by target tissues. The effects of exercise on 25(OH)D levels in the circulation may be dependent on many factors, such as the vitamin D nutritional status, exercise type and intensity, and sex. Therefore, further research on the effects and mechanisms of exercise on vitamin D metabolites is required.

Correlates of Calcidiol Deficiency in Adults-Cross-Sectional, Observational, Population-Based Study

The prevalence, determinants, and clinical significance of vitamin D deficiency in the population are debated. The population-based study investigated the cross-sectional associations of several variables with serum 25-hydroxyvitamin D (calcidiol) measured using standardized calibrators. The study cohort consisted of 979 persons of the Moli-sani study, both sexes, ages ≥35 years. The correlates in the analyses were sex, age, education, local solar irradiance in the month preceding the visit, physical activity, anthropometry, diabetes, kidney function, albuminuria, blood pressure, serum cholesterol, smoking, alcohol intake, calorie intake, dietary vitamin D intake, and vitamin D supplement. The serum calcidiol was log transformed for linear regression because it was positively skewed (skewness = 1.16). The prevalence of calcidiol deficiency defined as serum calcidiol ≤12 ng/mL was 24.5%. In multi-variable regression, older age, lower solar irradiance, lower leisure physical activity, higher waist/hip ratio, higher systolic pressure, higher serum cholesterol, smoking, lower alcohol intake, and no vitamin D supplement were independent correlates of lower serum calcidiol (95% confidence interval of standardized regression coefficient ≠ 0) and of calcidiol deficiency (95% confidence interval of odds ratio > 1). The data indicate that low serum calcidiol in the population could reflect not only sun exposure, age, and vitamin D supplementation but also leisure physical activity, abdominal obesity, systolic hypertension, hypercholesterolemia, smoking, and alcohol intake.

Smoking behavior and circulating vitamin D levels in adults: A meta-analysis

To determine the effect of smoking on circulating vitamin D in adults, we performed a meta-analysis. Literature before 9 May 2021 was retrieved from electronic literature databases such as EMBASE, PubMed, and Cochrane. The quality of the included studies was assessed by two researchers against the Newcastle-Ottawa scale and JBI Evidence-based Health Care Centre criteria. All eligible studies and statistical analyses were performed using STATA 14. Twenty-four studies with 11,340 participants meeting the criteria were included in the meta-analysis. The results of meta-analysis showed that the level of circulating 25(OH)D in smokers was lower than that in nonsmokers. A subgroup analysis based on vitamin D supplement use showed that both smokers who used vitamin D supplements and smokers who did not use vitamin D supplements had lower blood 25(OH)D levels compared with the control group. In addition, subjects were divided into different subgroups according to age for meta-analysis, and the results showed that the serum 25(OH)D level in each subgroup of smokers was lower than that in the control group. This meta-analysis revealed differences in circulating vitamin D levels between smokers and nonsmokers, with smokers likely to have lower circulating vitamin D levels.

A Literature Review of the Potential Impact of Medication on Vitamin D Status

In recent years, there has been a significant increase in media coverage of the putative actions of vitamin D as well as the possible health benefits that supplementation might deliver. However, the potential effect that medications may have on the vitamin D status is rarely taken into consideration. This literature review was undertaken to assess the degree to which vitamin D status may be affected by medication. Electronic databases were searched to identify literature relating to this subject, and study characteristics and conclusions were scrutinized for evidence of potential associations. The following groups of drugs were identified in one or more studies to affect vitamin D status in some way: anti-epileptics, laxatives, metformin, loop diuretics, angiotensin-converting enzyme inhibitors, thiazide diuretics, statins, calcium channel blockers, antagonists of vitamin K, platelet aggregation inhibitors, digoxin, potassium-sparing diuretics, benzodiazepines, antidepressants, proton pump inhibitors, histamine H2-receptor antagonists, bile acid sequestrants, corticosteroids, antimicrobials, sulphonamides and urea derivatives, lipase inhibitors, hydroxychloroquine, highly active antiretroviral agents, and certain chemotherapeutic agents. Given that the quality of the data is heterogeneous, newer, more robustly designed studies are required to better define likely interactions between vitamin D and medications. This is especially so for cytochrome P450 3A4 enzyme (CYP3A4)-metabolized medications. Nevertheless, this review suggests that providers of health care ought to be alert to the potential of vitamin D depletions induced by medications, especially in elderly people exposed to multiple-drug therapy, and to provide supplementation if required.

Vitamin D Sources, Metabolism, and Deficiency: Available Compounds and Guidelines for Its Treatment

Studies on vitamin/hormone D deficiency have received a vast amount of attention in recent years, particularly concerning recommendations, guidelines, and treatments. Moreover, vitamin D's role as a hormone has been confirmed in various enzymatic, metabolic, physiological, and pathophysiological processes related to many organs and systems in the human body. This growing interest is mostly due to the evidence that modest-to-severe vitamin D deficiency is widely prevalent around the world. There is broad agreement that optimal vitamin D status is necessary for bones, muscles, and one's general health, as well as for the efficacy of antiresorptive and anabolic bone-forming treatments. Food supplementation with vitamin D, or the use of vitamin D supplements, are current strategies to improve vitamin D levels and treat deficiency. This article reviews consolidated and emerging concepts about vitamin D/hormone D metabolism, food sources, deficiency, as well as the different vitamin D supplements available, and current recommendations on the proper use of these compounds.

Skeletal Muscle and the Maintenance of Vitamin D Status

Vitamin D, unlike the micronutrients, vitamins A, E, and K, is largely obtained not from food, but by the action of solar ultraviolet (UV) light on its precursor, 7-dehydrocholesterol, in skin. With the decline in UV light intensity in winter, most skin production of vitamin D occurs in summer. Since no defined storage organ or tissue has been found for vitamin D, it has been assumed that an adequate vitamin D status in winter can only be maintained by oral supplementation. Skeletal muscle cells have now been shown to incorporate the vitamin D-binding protein (DBP) from blood into the cell cytoplasm where it binds to cytoplasmic actin. This intracellular DBP provides an array of specific binding sites for 25-hydroxyvitamin D (25(OH)D), which diffuses into the cell from the extracellular fluid. When intracellular DBP undergoes proteolytic breakdown, the bound 25(OH)D is then released and diffuses back into the blood. This uptake and release of 25(OH)D by muscle accounts for the very long half-life of this metabolite in the circulation. Since 25(OH)D concentration in the blood declines in winter, its cycling in and out of muscle cells appears to be upregulated. Parathyroid hormone is the most likely factor enhancing the repeated cycling of 25(OH)D between skeletal muscle and blood. This mechanism appears to have evolved to maintain an adequate vitamin D status in winter.

Effects of resistance training on serum 25(OH) D concentrations in young men: a randomized controlled trial

Background

Previous studies indicated that serum 25-hydroxyvitamin D [25(OH)D] concentrations are positively associated with physical activity levels independent of sun exposure. However, the effect of resistance training on serum 25(OH) D concentrations remains unclear. Thus, this study aimed to examine the effect of chronic resistance training on serum 25(OH) D concentrations and determine whether 25(OH) D concentration variations are influenced by body composition changes.

Methods

Eighteen young men aged 19–39 years were randomly divided into a 12-week resistance training group (RT, n = 9) and non-exercise control group (CON, n = 9). The trial was undertaken in Shanghai University of Sport in Shanghai, China. Randomization and allocation to trial group were carried out by a central computer system. Serum 25(OH) D and intact parathyroid hormone concentrations were measured using commercially available enzyme-linked immunosorbent assay kits. Body composition was measured by dual-energy X-ray absorptiometry.

Results

The average serum 25(OH) D concentrations were 26.6 nmol/L at baseline. After the 12-week intervention program, serum 25(OH) D concentrations significantly increased in both groups. Serum 25(OH) D concentrations at midpoint (6-week) increased significantly only in the CON group (P < 0.01). From training midpoint to endpoint, a significantly greater increase in serum 25(OH) D concentrations was noted in the RT group (P-interaction = 0.043); 25(OH) D concentration changes (end-pre) were negatively related to fat-free mass (mid-pre) (r = − 0.565, P = 0.015) and muscle mass (mid-pre) (r = − 0.554, P = 0.017).

Conclusions

There were no beneficial effects of the 12-week resistance training on serum 25(OH) D concentration in vitamin D deficient young men, and an indication that seasonal increase in serum 25(OH) D concentrations during the early phase of resistance training was transiently inhibited, which may partly be attributed to resistance training-induced muscle mass gain.

Trial registration

Chinese Clinical Trial Registry, ChiCTR2000030876. Registered 16 March 2020 - Retrospectively registered, http://www.chictr.org.cn/showproj.aspx?proj=50504.

Association of circulating 25-hydroxyvitamin D levels with hypertension and blood pressure values in Korean adults: A Mendelian randomization study on a subset of the Korea National Health and Nutrition Survey 2011-2012 population

BACKGROUND/OBJECTIVES

Lower circulating 25-hydroxyvitamin D [25(OH)D] levels are associated with a higher risk of hypertension (HTN); however, it remains unclear whether the relationship is causal. We aimed to evaluate the causal effects of circulating 25(OH)D levels on the prevalence of HTN in the Korean population using the Mendelian randomization (MR) approach.

SUBJECTS/METHODS

Epidemiological data, serum 25(OH)D data, and genomic DNA biospecimens were obtained from 2,591 participants, a subset of the study population in the Korea National Health and Nutrition Survey 2011-2012. Five 25(OH)D-related single nucleotide polymorphisms (SNPs; DHCR7 rs12785878, CYP2R1 rs10741657, CYP2R1 rs12794714, CYP24A1 rs6013897, and GC rs2282679), identified a priori from genome-wide association studies, were used as instrument variables (IVs) for serum 25(OH)D levels. In the MR analysis, we performed IV analyses using the two-stage least squares method.

RESULTS

In the observational analysis, circulating 25(OH)D levels were found to be inversely associated with the HTN prevalence in ordinary least squares models (odds ratio: 0.97, 95% confidence interval: 0.96, 0.99) after adjusting for the potential confounders. There were differences in the circulating 25(OH)D levels across genotypes of individual SNPs. In the MR analysis, using individual SNPs as IVs, 25(OH)D levels were not associated with the HTN prevalence.

CONCLUSIONS

We found no association between genetically determined circulating 25(OH)D levels and HTN in Korean adults. Our results are listed owing to the relatively small sample size and possible weak instrument bias; therefore, further studies are needed to confirm these results.

Effects of Exercise Intervention Program on Bone Mineral Accretion in Children and Adolescents with Cystic Fibrosis: A Randomized Controlled Trial

OBJECTIVE

To evaluate effect of one year exercise intervention program on bone mineral accrual in children and adolescent with cystic fibrosis (CF).

METHODS

Fifty-two CF children (mean age 149.79 mo) were randomized into experimental (15 boys and 10 girls) and control groups (15 boys and 12 girls). Experimental group performed prescribed exercises three times/week, while control group continued with routine physical activities for one year. Following were assessed at baseline and at one year: Bone mineral density (BMD) of whole body and lumbar spine, pulmonary function, exercise capacity, quality of life and habitual activity.

RESULTS

Change in whole body and lumbar spine BMD over 12 mo in experimental group was lower by 0.006 g/cm² (95% CI -0.02 to 0.02) and higher by 0.001 g/cm² (95% CI -0.04 to 0.03) than controls, respectively. However, difference between groups was non-significant for both parameters. Experimental group had a significant improvement in their exercise capacity (p = 0.006), quality of life, and serum vitamin D (p = 0.007) levels. Differences between groups for changes in pulmonary function and habitual activity were non-significant.

CONCLUSIONS

Exercise regime was not associated with significant improvement in BMD of CF patients, but it had a positive impact on both physical and psychological health of these patients.

The Role of Skeletal Muscle in Maintaining Vitamin D Status in Winter

The status of vitamin D is determined mainly by its formation in skin by the photochemical action of solar UVB light (wavelength 290-320 nm) on the precursor 7-dehydrocholesterol. Because of seasonal variation in intensity of solar UV light, vitamin D status falls in winter and rises in summer. It has been presumed that there is no functional store of vitamin D. Thus, to avoid deficiency, a nutritional supply would be required in winter. However, there is now evidence that the main circulating metabolite of vitamin D, 25-hydroxyvitamin D, accumulates in skeletal muscle cells, which provide a functional store during the winter months. The mechanism is mediated by muscle cell uptake of circulating vitamin D-binding protein (DBP) through a megalin-cubilin membrane transport process. DBP then binds to cytoplasmic actin to provide an array of high-affinity binding sites for 25-hydroxyvitamin D [25(OH)D]. The repeated passage of 25(OH)D into and out of muscle cells would account for its long residence time in blood.

Association between leisure-time aerobic physical activity and vitamin D concentrations among US older adults: the NHANES 2007-2012

BACKGROUND

Although previous studies have described a positive correlation between physical activity and 25-hydroxyvitamin D concentrations (25(OH)D), there have been inconsistent results in regard to the frequency or intensity of physical activity needed to achieve adequate 25(OH)D status.

AIMS

To examine the relationship between self-reported leisure-time physical activity and 25(OH)D₃ and 25(OHD) concentrations among US adults aged 60 years and older.

METHODS

The present analysis was based on data from participants in the National Health and Nutrition Examination Survey 2007-2012. Moderate or vigorous leisure-time physical activity was calculated by min/week or metabolic equivalent task scores-minutes/week and defined according to the 2008 Physical Activity Guidelines for Americans. General linear models adjusted for confounders were created to compare mean 25(OH)D and 25(OH)₃ concentrations across physical activity status.

RESULTS

A total of 4764 adults with a mean age of 69.7 years comprised the study sample. Overall, 33.3% men and 23.1% women were defined as physically active and participants' mean 25(OH)D and 25(OH)D₃ concentration was 75.0 and 68.8 nmol/L, respectively. Older adults physically active had 8.1 and 7.1 nmol/L higher 25(OH)D and 25(OH)₃ levels than those physically inactive, respectively. Moreover, higher 25(OH)D₃ and 25(OH)D concentrations were consistently seen during the summer and autumn months. In contrast, sedentary older adults had on average 25(OH)D levels < 75 nmol/L irrespective of the 6-month study period examined.

CONCLUSIONS

Leisure-time physical activity appears to be an effective manner of maintaining adequate vitamin D concentrations later in life. Therefore, promoting physical activity in older adults should be a national public health priority.

Determinants of vitamin D status of healthy office workers in Sydney, Australia

Low vitamin D status, measured as 25-hydroxyvitamin D (25OHD), has been linked to increased risk of osteoporosis and other disorders. Due to the indoor nature of office work, there may be an increased risk of 25OHD deficiency in this group. The aim of the current study was to evaluate seasonal variations of 25OHD in a population of healthy office workers, and to assess the effect of sun exposure behaviour, skin pigmentation, physical activity (PA) and dietary intake on serum 25OHD concentrations. We assessed the vitamin D status of healthy office workers in Sydney, Australia, at the end of summer (n = 103) and then at the end of winter (n = 71). Data on anthropometry, PA, dietary intake, sun exposure and skin phototype were collected along with blood samples. Serum 25OHD was measured by radioimmunoassay. Mean 25OHD concentration in late summer was 68 ± 27 nmol/L (range: 24-160 nmol/L), and in late winter was 59 ± 32 nmol/L (range: 15-174 nmol/L). 25OHD deficiency (<50 nmol/L) was observed in 29% and 42% of participants at end-summer and end-winter, respectively. Almost 10% of individuals were extremely deficient (<25 nmol/L) at end-winter, particularly those with dark skin (phototypes 5 and 6). Independent predictors of end-summer 25OHD were skin phototype (p < 0.02), summer sun exposure (p < 0.001) and skin area exposed (p = 0.005). The strongest predictor of end-winter 25OHD was end-summer 25OHD concentration (p < 0.001). If this was excluded from the model, the independent predictors of end-winter 25OHD were skin phototype (p < 0.01), sun exposure in winter (p = 0.01) and oily fish consumption (p < 0.05). Sunscreen use was significantly associated with higher vitamin D status (p < 0.05) as those who used sunscreen were also more likely to spend time outdoors. We conclude that sun exposure is beneficial for vitamin D status even with sunscreen use. Vitamin D supplements should be targeted to individuals who are darker skinned or unable to obtain adequate sun exposure, particularly during the winter months.

Vitamin D status among adolescents in Kuwait: a cross-sectional study

OBJECTIVES

In Kuwait, as in many Arab states in the Gulf region, there are limited data on the prevalence of vitamin D deficiency among healthy adolescents. This study aimed to estimate the prevalence of vitamin D deficiency in a nationally representative sample of adolescents and investigate factors associated with vitamin D status.

METHODS

A cross-sectional study was conducted on 1416 adolescents aged 11-16 years, who were randomly selected from middle schools in all governorates of Kuwait. Data were collected from parents through self-administered questionnaire and from adolescents through face-to-face interview. Vitamin D was measured using liquid chromatography-tandem mass spectrometry. Logistic regression was used to investigate the independent factors associated with vitamin D status.

RESULTS

The prevalence of vitamin D deficiency was 81.21% (95% CI 71.61% to 90.81%), while severe deficiency was 39.48%. Only 3.60% of adolescents were vitamin D-sufficient. The prevalence of vitamin D deficiency was significantly higher among girls compared with boys (91.69% vs 70.32%; p<0.001). There was a significant inverse correlation between vitamin D and parathyroid hormone (Spearman correlation=-0.35; p<0.001). In the final model, gender, age, governorate, parental education, body mass index, vitamin D supplement and the number of times adolescents walk to schools per week were all significantly related to vitamin D deficiency.

CONCLUSION

High prevalence of vitamin D deficiency was noted among adolescents in Kuwait despite the abundant sunshine, which may reflect strong sun avoidance behaviour. Adequate outdoor daytime activities should be encouraged especially for girls. We call for locally tailored guidelines for vitamin D supplement in which girls should have a higher dose compared with boys.

Sunlight exposure is just one of the factors which influence vitamin D status

Studies on the determinants of vitamin D status have tended to concentrate on input - exposure to ultraviolet B radiation and the limited sources in food. Yet, vitamin D status, determined by circulating concentrations of 25-hydroxyvitamin D (25(OH)D), can vary quite markedly in groups of people with apparently similar inputs of vitamin D. There are small effects of polymorphisms in the genes for key proteins involved in vitamin D production and metabolism, including 7-dehydrocholesterol reductase, which converts 7-dehydrocholesterol, the precursor of vitamin D, to cholesterol, CYP2R1, the main 25-hydroxylase of vitamin D, GC, coding for the vitamin D binding protein which transports 25(OH)D and other metabolites in blood and CYP24A1, which 24-hydroxylates both 25(OH)D and the hormone, 1,25-dihydroxyvitamin D. 25(OH)D has a highly variable half-life in blood. There is evidence that the half-life of 25(OH)D is affected by calcium intake and some therapeutic agents. Fat tissue seems to serve as a sink for the parent vitamin D, which is released mainly when there are reductions in adiposity. Some evidence is presented to support the proposal that skeletal muscle provides a substantial site of sequestration of 25(OH)D, protecting this metabolite from degradation by the liver, which may help to explain why exercise, not just outdoors, is usually associated with better vitamin D status.

Contribution of sun exposure to the vitamin D dose received by various groups of the Spanish population

Although the harmful effects of excessive exposure to solar ultraviolet (UV) radiation are well known, the recommended dose of UV radiation is beneficial for the synthesis of vitamin D by the skin, in addition to being useful in the treatment of various illnesses and mental problems. Numerous studies have shown that vitamin D performs important functions in the human organism, such as absorbing calcium and phosphorous and contributing to the immune system, among others. Several studies have found that a high percentage of various groups of the Spanish population suffer from vitamin D deficiency, and since very few natural foods contain vitamin D, it was considered important to determine whether groups such as schoolchildren, outdoor workers and athletes, receive enough solar radiation to produce adequate levels of vitamin D in their daily activities. It was found that the amount of vitamin D (in IU) produced by personal effective solar UV doses could exceed the recommended dose of 1000IU/day in spring and summer, while the winter estimate (about 220IU/day) is only one quarter of the recommended dose. These results suggest that most people would not receive the recommended daily vitamin D dose in winter from exposure to solar UV radiation, the main source of vitamin D.

Effects of chronic endurance exercise training on serum 25(OH)D concentrations in elderly Japanese men

BACKGROUND

Higher levels of physical activity and cardiorespiratory fitness are positively related to serum 25-hydroxyvitamin D [25(OH)D] concentrations; however, the response of 25(OH)D concentrations to chronic endurance exercise training is unclear. Therefore, the purpose of this study was to elucidate whether serum 25(OH)D concentrations were directly increased by 5 weeks of endurance exercise training and influenced by changes in body fat in elderly men.

METHODS

Twenty elderly Japanese men were randomized to either the 5-week endurance exercise training group (ET group; N = 10) or the sedentary control group (SC group; N = 10). Fasting blood samples were collected to determine serum 25(OH)D and other blood parameters. The visceral fat area and hepatic fat content were assessed by magnetic resonance imaging and proton magnetic resonance spectroscopy, respectively.

RESULTS

After 5 weeks of endurance exercise training, the levels of maximal oxygen uptake (VO₂ max) were significantly increased from 23.3 at baseline to 28.1 mL/kg/min at the endpoint for the ET group; levels were unchanged for the SC group. A significant seasonal reduction in serum 25(OH)D concentrations was observed in the SC group (P < 0.05), while no change was found in the ET group. The results may be partly attributed to the slight decrease in intrahepatic fat in the ET group. No changes were observed in percent body fat or visceral fat area.

CONCLUSIONS

The results of our study suggest that 5 weeks of endurance training could inhibit the seasonal reduction in serum 25(OH)D concentrations without changes in body fat.

Role of Parathyroid Hormone in Determination of Fat Mass in Patients with Vitamin D Deficiency

BACKGROUND

Obesity has become a global epidemic and it is rising is Asia. Vitamin D deficiency (VDD) is widely prevalent in the Indian subcontinent. Studies have linked VDD to obesity and shown correlation between parathyroid hormone (PTH), 25-hydroxy Vitamin D (25(OH)D), and fat mass (FM). However, studies on the role of PTH among subjects with VDD are lacking.

OBJECTIVE

The objective of this study is to study the role of PTH in the determination of FM in participants with VDD.

SUBJECTS

Five hundred and fifty-one adults (m:247, f:304) were included in this study.

MATERIALS AND METHODS

Total and regional (trunk, arm, and leg) FM was assessed by dual X-ray absorptometry. Biochemical and hormonal parameters such as calcium, phosphorus, alkaline phosphatase, ionic calcium, 25(OH)D, and PTH were also analyzed.

RESULTS

The mean age of the study population was 58.8 ± 15.8 years (Male: [63.3 ± 13.1], Female: [55.2 ± 16.9]). FM and body mass index were significantly lower in females with higher levels of serum 25(OH)D. Total FM was negatively correlated with serum 25(OH)D (r = -0.363, P < 0.0001) and positively correlated with serum PTH (r: 0.262, P < 0.0001) in females only. Females with VDD and secondary hyperparathyroidism had higher FM than those with normal PTH.

CONCLUSIONS

Females with VDD had higher total and regional FM. However, this correlation was evident only in those with high serum PTH levels, suggesting a potential role of PTH in the accumulation of FM.

Effect of an Acute Bout of Endurance Exercise on Serum 25(OH)D Concentrations in Young Adults

CONTEXT

Regular exercise or high physical activity levels are associated with higher serum 25-hydroxyvitamin D [25(OH)D] concentrations; however, the effect of acute exercise on serum 25(OH)D concentrations remains unclear.

OBJECTIVE

We aimed to clarify whether acute endurance exercise has a direct effect on the circulating 25(OH)D concentrations in young adults.

DESIGN AND SETTING

Exercise intervention trial in an institutional practice.

PATIENTS

Twenty young, active adults (males, n = 10; females, n = 10).

INTERVENTIONS

Participants were asked to perform a cycling exercise for 30 minutes at 70% maximal oxygen uptake.

MAIN OUTCOME MEASURES

The serum concentrations of 25(OH)D and other blood parameters were assessed before exercise and at 0, 0.5, 1, 3, and 24 hours after exercise.

RESULTS

The serum 25(OH)D concentrations were significantly increased not only at 0 (P < 0.01), 1 (P < 0.05), and 3 hours (P < 0.01) after exercise, but they were also increased at 24 hours (P < 0.05) after acute endurance exercise in young adults. A significant sex × time interaction effect was observed (P < 0.05), and the incremental areas under the curve for the 25(OH)D concentrations were significantly higher in men than in the women (P < 0.01).

CONCLUSIONS

There is a direct effect of endurance exercise on serum 25(OH)D concentrations. In addition, sex disparity was observed in the serum 25(OH)D response to acute endurance exercise, and the increase in 25(OH)D concentrations was greater in men than in women.

The effect of parathyroid hormone on the uptake and retention of 25-hydroxyvitamin D in skeletal muscle cells

Data from our studies, and those of others, support the proposal that there is a role for skeletal muscle in the maintenance of vitamin D status. We demonstrated that skeletal muscle is able to internalise extracellular vitamin D binding protein, which then binds to actin in the cytoplasm, to provide high affinity binding sites which accumulate 25-hydroxyvitamin D₃ (25(OH)D₃) [1]. This study investigated the concentration- and time-dependent effects of parathyroid hormone (PTH) on the capacity of muscle cells to take up and release ³H-25(OH)D₃. Uptake and retention studies for ³H-25(OH)D₃ were carried out with C2C12 cells differentiated into myotubes and with primary mouse muscle fibers as described [1]. The presence of PTH receptors on mouse muscle fibers was demonstrated by immunohistochemistry and PTH receptors were detected in differentiated myotubes, but not myoblasts, and on muscle fibers by Western blot. Addition of low concentrations of vitamin D binding protein to the incubation media did not alter uptake of 25(OH)D₃. Pre-incubation of C2 myotubes or primary mouse muscle fibers with PTH (0.1 to 100 pM) for 3h resulted in a concentration-dependent decrease in 25(OH)D₃ uptake after 4 or 16h. These effects were significant at 0.1 or 1pM PTH (p<0.001) and plateaued at 10pM, with 25(OH)D₃ uptake reduced by over 60% (p<0.001) in both cell types. In C2 myotubes, retention of 25(OH)D₃ was decreased after addition of PTH (0.1 to 100pM) in a concentration-dependent manner by up to 80% (p<0.001) compared to non-PTH treated-C2 myotubes. These data show that muscle uptake and retention of 25(OH)D₃ are modulated by PTH, a physiological regulator of mineral homeostasis, but the cell culture model may not be a comprehensive reflection of vitamin D homeostatic mechanisms in whole animals.

25-hydroxyvitamin D is associated with adiposity and cardiometabolic risk factors in a predominantly vitamin D-deficient and overweight/obese but otherwise healthy cohort

Vitamin D deficiency has reached epidemic proportions worldwide and has recently been linked to cardiometabolic risk factors including obesity, insulin resistance, hypertension, dyslipidemia, as well as type 2 diabetes and cardiovascular disease. The objective of this study was to examine the associations between circulating 25-hydrovitamin D (25(OH)D) levels and cardiometabolic risk factors using direct measures of adiposity, glucose intolerance, and insulin resistance, as well as lipids, blood pressure, and plasma markers of inflammation. We measured circulating 25(OH)D, physical activity (International Physical Activity Questionnaire- IPAQ), anthropometry (body mass index (BMI), waist-to-hip ratio (WHR), % body fat (dual energy X-ray absorptiometry)), metabolic parameters (fasting and 2-h plasma glucose levels during oral glucose tolerance test; insulin sensitivity (M, hyperinsulinaemic-euglycaemic clamp), and cardiovascular and inflammatory profiles (blood pressure (BP), pulse pressure (PP), mean arterial pressure (MAP), plasma lipid levels, white blood cell count (WBC), and plasma high-sensitivity C-reactive protein levels (hsCRP)) in 111 healthy, non-diabetic adults (66 males/45 females; age 31.1±9.2years; % body fat 36.0±10.2%). Mean 25(OH)D was 39.8±19.8 nmol/L with no difference between genders (p=0.4). On univariate analysis, 25(OH)D was associated with% body fat (r=-0.27; p=0.005), 2-h glucose (r=-0.21; p=0.03), PP (r=0.26; p=0.006), and insulin sensitivity (r=0.20, p=0.04), but not with age, BMI, WHR, fasting glucose, BP, MAP, lipids, or inflammatory markers (all p>0.05). After adjusting for age and sex, 25(OH)D remained associated with% body fat (β=-0.12%; p=0.003), 2-h glucose (β=-0.13mmol/L; p=0.02), PP (β=0.12mmHg; p=0.009), and insulin sensitivity (β=0.22mg/kg/min; p=0.03), and became associated with fasting glucose (β=-0.04mmol/L; p=0.04) and hsCRP (β=-0.51mg/L; p=0.04). After adjusting for age, sex, and % body fat, 25(OH)D was no longer associated with insulin sensitivity, 2-h glucose, or hsCRP, but remained associated with fasting glucose (β=-0.05mmol/L; p=0.03) and PP (β=0.10mmHg; p=0.03). 25(OH)D remained associated with fasting glucose (β=-0.06mmol/L; p=0.02) after hsCRP and physical activity were added to the model with % body fat, age, and sex. ​These cross-sectional data suggest that associations between vitamin D and cardiometabolic risk among healthy, non-diabetic adults are largely mediated by adiposity. Large-scale intervention and mechanistic studies are needed to further investigate whether vitamin D has an independent role in the prevention and/or management of cardiometabolic risk and disease.

Plasma 25-Hydroxyvitamin D3 Levels in Colorectal Cancer Patients and Associations with Physical Activity

Physical activity (PA) and vitamin D are thought to affect colorectal cancer prognosis. The present study investigates associations between 25(OH)D₃ and PA in prospectively followed colorectal cancer patients in the ColoCare study. At 6, 12, and 24 mo after surgery, patients donated a blood sample, wore an accelerometer for 10 consecutive days, and completed a PA questionnaire. Plasma 25-hydroxyvitamin D₃ (25(OH)D₃) levels were measured by high-performance liquid chromatography. We tested associations using partial correlations and multivariate linear regression analysis, adjusted for season, age, and body mass index. A total of 137 assessments of 25(OH)D₃ levels and PA were conducted (58 at 6 mo, 51 at 12 mo, and 28 at 24 mo). More than 60% of the patients were vitamin D-deficient (25(OH)D₃ ≤20 ng/ml), independent of study time point. At 6-mo follow-up, accelerometry-based vigorous and moderate-to-vigorous PAs were positively associated with 25(OH)D₃ levels (P = 0.04; P = 0.006,). PA together with season was a significant predictor of elevated 25(OH)D₃ levels. Our results suggest that the majority of colorectal cancer patients may suffer from vitamin D deficiency. Engaging in PA may be an effective approach to increase their 25(OH)D₃ levels.

A comparison of the direct medical costs for individuals with or without basal or squamous cell skin cancer: A study from Australia

Objectives:

The composition of the medical costs incurred by people treated for basal cell and squamous cell carcinomas (hereafter keratinocyte cancers) is not adequately understood. We sought to compare the medical costs of individuals with or without keratinocyte cancers.

Methods:

We used national health insurance data to analyze the direct medical costs of 2000 cases and 2000 controls nested within the QSkin prospective cohort study (n = 43,794) conducted in Australia. We reconstructed the medical history of patients using medical and pharmaceutical item codes and then compared the health service costs of individuals treated for keratinocyte cancers with those not treated for keratinocyte cancers.

Results:

Individuals treated for keratinocyte cancers consumed on average AUD$1320 per annum more in medical services than those without keratinocyte cancers. Only 23.2% of costs were attributed to the explicit treatment of keratinocyte cancers. The principal drivers of the residual costs were medical attendances, surgical procedures on the skin, and histopathology services. We found significant positive associations between history of treatment for keratinocyte cancers with treatments for other health conditions, including melanoma, cardiovascular disease, lipidemia, osteoporosis, rheumatoid arthritis, colorectal cancer, prostate cancer, and tuberculosis.

Conclusion:

Individuals treated for keratinocyte cancers have substantially higher medical costs overall than individuals without keratinocyte cancers. The direct costs of skin cancer excision account for only one-fifth of this difference.

Is the Association between Vitamin D and Cardiovascular Disease Risk Confounded by Obesity? Evidence from the Andhra Pradesh Children and Parents Study (APCAPS)

Background

Evidence of an association between serum vitamin D and cardiovascular disease risk is inconsistent and comes predominantly from studies in high-income settings. We assessed the association between serum levels of 25-hydroxyvitamin D₃ (25(OH)D) and cardiovascular disease risk factors in a population of young Indian adults.

Methods

Cross-sectional analyses of data from APCAPS (Andhra Pradesh Children and Parents Study); a prospective birth cohort study in rural south India. Participants were 1038 (40.3% females) adults aged 18-24 years. Main outcome measures were blood pressures, fasting serum lipids (cholesterols and triglycerides), fasting glucose, insulin, measures of arterial stiffness (aortic augmentation index and aortic pulse wave velocity (aPWV)), carotid intima-media thickness, body mass index (BMI) and body fat (dual X-ray absorptiometry).

Results

Vitamin D deficiency (≤20ng/ml) was observed in 41.1% of this lean (mean BMI: 19.5) and active (mean minutes of moderate or vigorous physical activity per day: 186) population. Vitamin D deficiency was associated with higher median body fat in both males (15.9% body fat in vitamin D deficient males vs. 14.6% in non-deficient males, p<0.05) and females (29.1% body fat in vitamin D deficient females vs. 27.8% in non-deficient females, p<0.05) but no associations were observed between vitamin D deficiency and mean BMI or median fat mass index (FMI). Except a weak inverse association with fasting insulin in males, there was no clear association between serum vitamin D levels and cardiovascular disease risk factors in fully adjusted models.

Conclusions

We did not find clear evidence for an association between serum vitamin D levels and cardiovascular disease risk factors. Our results, consistent with the limited evidence from randomised trials of vitamin D supplementation and Mendelian randomisation experiments, suggest that the postulated link between serum vitamin D and cardiovascular disease may be non-causal. Instead, it may be attributable to confounding by lifestyle factors such as obesity and physical inactivity which may provide more fruitful targets for cardiovascular disease prevention.

Vitamin D and parathyroid hormone status in a representative population living in Macau, China

Associations between documented sun-exposure, exercise patterns and fish and supplement intake and 25-hydroxyvitamin D (25OHD) and parathyroid hormone (PTH) were investigated in a random household survey of Macau residents (aged 18-93). Blood samples (566) taken in summer were analyzed for 25OHD and PTH. In this Chinese population, 55% were deficient (25OHD <50nmol/L: median (interquartile range)=47.7 (24.2) nmol/L). Vitamin D deficiency was greatest in those aged <50 years: median (interquartile range)=43.3 (18.2) nmol/L, females: median (interquartile range)=45.5 (19.4) nmol/L and those with higher educational qualifications: median (interquartile range)=43.1 (18.7) nmol/L. In the total Macau population, statistically significant (p<0.01) modifiable associations with lower 25OHD levels were sunlight exposure (β=0.06), physical activity (PA) (measured as hours(hrs)/day: β=0.08), sitting (measured as hrs/day β=-0.20), intake of fish (β=0.08) and calcium (Ca) supplement intake (β=0.06) [linear regression analysis adjusting for demographic risk factors]. On similar analysis, and after adjustment for 25OHD, the only significant modifiable associations in the total population with PTH were sitting (β=-0.17), Body Mass Index (β=0.07) and Ca supplement intake (β=-0.06). In this Macau population less documented sun exposure, fish and Ca supplement intake and exercise were associated with lower 25OHD levels, especially in the younger population, along with the interesting finding that more sitting was associated with both lower 25OHD and high PTH blood levels. In conclusion, unlike findings from Caucasian populations, younger participants were significantly more vitamin D deficient, in particular highly educated single females. This may indicate the desire of young females to be pale and avoid the sun. There are also big differences in lifestyle between the older generation and the younger, in particular with respect to sun exposure and PA. This article is part of a Special Issue entitled '17th Vitamin D Workshop'.

A reconstruction of a medical history from administrative data: with an application to the cost of skin cancer

The medical record is a repository of clinical data, which can greatly enhance the quality of health and healthcare analysis. Administrative data are collected for the purpose of billing and reimbursement, and are valued by health researchers because the data are routinely audited to maintain accurate financial records. However, the quantity of incorporated clinical data can be variable. In this paper we reconstruct the medical record from health service invoices to estimate the cost of treating keratinocytic cancer (KC). The data from an epidemiological survey were linked to an administrative data set supplied by the national health insurer. A matched sampling technique with multivariable analysis was used to estimate cost. A KC treatment was identified with 42 service codes which explicitly nominated treatment of a KC. Algorithms identifying comorbities potentially correlated with KC were constructed from the service codes. The annual cost of a KC treatment was estimated to be AU$667 per individual. The average cost of explicit KC treatments was AU$231, while the cost of generic procedures used to treat KC was AU$436. Our ability to accurately control for the medical history enabled our analysis to quantify and describe the constituent costs of KC treatment.

Building healthy bones throughout life: an evidence-informed strategy to prevent osteoporosis in Australia

Osteoporosis imposes a tremendous burden on Australia: 1.2 million Australians have osteoporosis and 6.3 million have osteopenia. In the 2007–08 financial year, 82 000 Australians suffered fragility fractures, of which > 17 000 were hip fractures. In the 2000–01 financial year, direct costs were estimated at $1.9 billion per year and an additional $5.6 billion on indirect costs. Osteoporosis was designated a National Health Priority Area in 2002; however, implementation of national plans has not yet matched the rhetoric in terms of urgency. Building healthy bones throughout life, the Osteoporosis Australia strategy to prevent osteoporosis throughout the life cycle, presents an evidence-informed set of recommendations for consumers, health care professionals and policymakers. The strategy was adopted by consensus at the Osteoporosis Australia Summit in Sydney, 20 October 2011. Primary objectives throughout the life cycle are: to maximise peak bone mass during childhood and adolescence to prevent premature bone loss and improve or maintain muscle mass, strength and functional capacity in healthy adults to prevent and treat osteoporosis in order to minimise the risk of suffering fragility fractures, and reduce falls risk, in older people. The recommendations focus on three affordable and important interventions — to ensure people have adequate calcium intake, vitamin D levels and appropriate physical activity throughout their lives. Recommendations relevant to all stages of life include: daily dietary calcium intakes should be consistent with Australian and New Zealand guidelines serum levels of vitamin D in the general population should be above 50nmol/L in winter or early spring for optimal bone health regular weight-bearing physical activity, muscle strengthening exercises and challenging balance/mobility activities should be conducted in a safe environment.

Association between serum vitamin D status and metabolic syndrome in Korean young men

PURPOSE

This study examined the relations of serum vitamin D levels to body fatness, cardiorespiratory fitness (CRF), and metabolic risk factors in young adults in Korea.

METHODS

Between 2007 and 2009, 799 young men completed a health examination. Body fatness, CRF based on a maximal treadmill exercise test, and measurements of metabolic risk factors were measured in study participants. Participants were classified by serum vitamin D levels as deficient (<12.5 ng·mL), insufficient (≥12.5 to <20 ng·mL), and sufficient (>20 ng·mL) and by CRF as unfit (lowest 20%) and fit (remaining 80%) based on age-standardized distribution of V˙O2max values in this study population. Body fatness, CRF, and metabolic risk factors were evaluated according to serum vitamin D classification. A clustered metabolic risk score was computed by summing standardized scores for waist circumference, resting blood pressures, triacylglycerols, the inverse of high-density lipoprotein cholesterol, glucose, and insulin.

RESULTS

Linear decreases in body fatness and metabolic risk factors were observed, as was a linear increase for CRF across incremental vitamin D categories. A linear decrease was found in the clustered metabolic risk score across incremental vitamin D categories. Compared to the fit group (reference), the unfit group had significantly higher risks for serum vitamin D inadequacy before and after adjusting for age, smoking, and body fatness parameters.

CONCLUSIONS

The findings of the study suggest that increasing vitamin D intake, eating a healthy diet, and getting enough outdoor physical activity should be promoted as nonpharmacologic means to improve CRF and prevent a clustering of metabolic risk factors in young adults.

Uptake of 25-hydroxyvitamin D by muscle and fat cells

Vitamin D status, measured as serum 25-hydroxyvitamin D (25OHD) concentration, is determined by rates of input and of degradation. The half-life of 25OHD is surprisingly long for a steroid and much longer than its blood transporter, vitamin D binding protein. There is some evidence to suggest that vitamin D itself is stored in fat, whereas 25OHD concentrations are usually related to muscle-related parameters such as lean body mass and exercise. Both muscle and fat cells come from the mesenchymal cell lineage. We recently published evidence for net uptake of 25OHD into differentiated muscle cells, in a process that was megalin dependent, and speculated that this uptake might contribute to the extended half-life of 25OHD. Whether 25OHD is also taken up into cells of the adipocyte lineage is not clear. In the current study, we used the C2 muscle cell line as a source of myoblasts that were differentiated in culture to myotubes and 3T3-L1 pre-adipocytes that were differentiated into adipocytes in culture. We incubated the cells with trititated 25OHD and measured net uptake 4 and 16h afterwards. Differentiated myotubes took up labeled 25OHD in a time-dependent process to a far greater extent than myoblasts. In contrast, pre-adipocytes, but not differentiated adipocytes, accumulated labeled 25OHD in a time-dependent manner, though to a lesser extent than myotubes. Myotubes, but not myoblasts, showed megalin expression by immunohistochemistry. Pre-adipocytes, but not adipocytes, also showed expression of megalin. Since skeletal muscle consists mainly of differentiated muscle cells, while adipose tissue is mainly differentiated fat cells, it seems likely that muscle, but not fat tissue, provides a large extravascular pool through which 25OHD circulates and that this protects 25OHD from degradation. This article is part of a Special Issue entitled '16th Vitamin D Workshop'.

Association of serum 25-hydroxyvitamin D with lifestyle factors and metabolic and cardiovascular disease markers: population-based cross-sectional study (FIN-D2D)

Objectives

Low serum 25-hydroxyvitamin D (25OHD) level has been associated with an increased risk of several chronic diseases. Our aim was to determine lifestyle and clinical factors that are associated with 25OHD level and to investigate connection of 25OHD level with metabolic and cardiovascular disease markers.

Design

In total, 2868 Finnish men and women aged 45–74 years participated in FIN-D2D population-based health survey in 2007. Participants that had a serum sample available (98.4%; n = 2822) were included in this study. 25OHD was measured with chemiluminescent microparticle immunoassay method.

Results

The mean 25OHD level was 58.2 nmol/l in men (n = 1348) and 57.1 nmol/l in women (n = 1474). Mean 25OHD level was lower in the younger age groups than in the older ones (p<0.0001 both in men and women). This study confirmed that low physical activity (p<0.0001 both in men and women), smoking (p = 0.0002 in men and p = 0.03 in women) and high BMI (p<0.0001 in women) are factors that independently associate with low 25OHD level. Of the metabolic and cardiovascular disease markers high triglyceride concentration (p = 0.02 in men and p = 0.001 in women) and high apolipoprotein B/apolipoprotein A1 ratio (p = 0.04 in men and p = 0.03 in women) were independently associated with low 25OHD level.

Conclusions

Higher age did not predict lower 25OHD level in this study population of aged 45–74 years which may derive from a healthy life-style of “active pensioners”. Low physical activity and smoking came up as independent lifestyle factors associated with low 25OHD level. Defining the molecular mechanisms behind the associations of 25OHD with low physical activity and smoking are important objective in future studies. The association of 25OHD with BMI, high triglyceride concentration and apolipoprotein B/apolipoprotein A1 ratio may be related to the role of vitamin D in inflammation, but more detailed studies are needed.

Relationship between vitamin D deficiency and cardiovascular disease

Epidemiological studies have found that low 25-hydroxyvitamin D levels may be associated with coronary risk factors and adverse cardiovascular outcomes. Additionally, vitamin D deficiency causes an increase in parathyroid hormone, which increases insulin resistance and is associated with diabetes, hypertension, inflammation, and increased cardiovascular risk. In this review, we analyze the association between vitamin D supplementation and the reduction in cardiovascular disease. The role of vitamin D deficiency in cardiovascular morbidity and mortality is still controversial, and larger scale, randomized placebo controlled trials are needed to investigate whether oral vitamin D supplementation can reduce cardiovascular risk. Given the low cost, safety, and demonstrated benefit of higher 25-hydroxyvitamin D levels, vitamin D supplementation should become a public health priority for combating common and costly chronic cardiovascular diseases.

Vitamin D status of Canadians employed in northern latitudes

BACKGROUND

Vitamin D deficiency and insufficiency are prevalent worldwide, but relatively few studies have examined vitamin D status in working populations.

AIMS

To assess the prevalence of vitamin D deficiency and insufficiency in Canadian workers and investigate risk factors in this population.

METHODS

A cross-sectional study using data from a health programme enrolling workers mostly from Northern Alberta, Canada. As part of the programme, volunteers were invited to complete a lifestyle questionnaire. Blood was taken to determine plasma 25-hydroxyvitamin D (25(OH)D) levels. Logistic and linear regressions were used to investigate the relationships between individual characteristics and vitamin D status.

RESULTS

Between October 2007 and December 2012, 6101 eligible workers enrolled in the health programme. The prevalence of vitamin D deficiency (plasma 25(OH)D, levels <27.5 nmol/l) and insufficiency (<37.5 nmol/l) were 3 and 8%, respectively. Male employees were significantly more likely to be vitamin D deficient and insufficient than females. Residing at a more northern latitude increased the likelihood of vitamin D deficiency and insufficiency. Age, assessments made in summer, better general health and physical activity and use of vitamin D supplementation were all related to lower likelihood of deficiency and insufficiency.

CONCLUSIONS

Vitamin D deficiency and insufficiency are a concern in this sample of Canadian workers. Vitamin D supplementation is recommended to reduce the prevalence of deficiency and insufficiency in this group.

Evidence for a specific uptake and retention mechanism for 25-hydroxyvitamin D (25OHD) in skeletal muscle cells

Little is known about the mechanism for the prolonged residence time of 25-hydroxyvitamin D (25OHD) in blood. Several lines of evidence led us to propose that skeletal muscle could function as the site of an extravascular pool of 25OHD. In vitro studies investigated the capacity of differentiated C2 murine muscle cells to take up and release 25OHD, in comparison with other cell types and the involvement of the membrane protein megalin in these mechanisms. When C2 cells are differentiated into myotubes, the time-dependent uptake of labeled 25OHD is 2-3 times higher than in undifferentiated myoblasts or nonmuscle osteoblastic MG63 cells (P < .001). During in vitro release experiments (after 25OHD uptake), myotubes released only 32% ± 6% stored 25OHD after 4 hours, whereas this figure was 60% ± 2% for osteoblasts (P < .01). Using immunofluorescence, C2 myotubes and primary rat muscle fibers were, for the first time, shown to express megalin and cubilin, endocytotic receptors for the vitamin D binding protein (DBP), which binds nearly all 25OHD in the blood. DBP has a high affinity for actin in skeletal muscle. A time-dependent uptake of Alexafluor-488-labeled DBP into mature muscle cells was observed by confocal microscopy. Incubation of C2 myotubes (for 24 hours) with receptor-associated protein, a megalin inhibitor, led to a 40% decrease in 25OHD uptake (P < .01). These data support the proposal that 25OHD, after uptake into mature muscle cells, is held there by DBP, which has been internalized via membrane megalin and is retained by binding to actin.

A systematic review of vitamin D status in populations worldwide

Vitamin D deficiency is associated with osteoporosis and is thought to increase the risk of cancer and CVD. Despite these numerous potential health effects, data on vitamin D status at the population level and within key subgroups are limited. The aims of the present study were to examine patterns of 25-hydroxyvitamin D (25(OH)D) levels worldwide and to assess differences by age, sex and region. In a systematic literature review using the Medline and EMBASE databases, we identified 195 studies conducted in forty-four countries involving more than 168 000 participants. Mean population-level 25(OH)D values varied considerably across the studies (range 4·9-136·2 nmol/l), with 37·3 % of the studies reporting mean values below 50 nmol/l. The highest 25(OH)D values were observed in North America. Although age-related differences were observed in the Asia/Pacific and Middle East/Africa regions, they were not observed elsewhere and sex-related differences were not observed in any region. Substantial heterogeneity between the studies precluded drawing conclusions on overall vitamin D status at the population level. Exploratory analyses, however, suggested that newborns and institutionalised elderly from several regions worldwide appeared to be at a generally higher risk of exhibiting lower 25(OH)D values. Substantial details on worldwide patterns of vitamin D status at the population level and within key subgroups are needed to inform public health policy development to reduce risk for potential health consequences of an inadequate vitamin D status.

A global representation of vitamin D status in healthy populations

PURPOSE

This paper visualizes the available data on vitamin D status on a global map, examines the existing heterogeneities in vitamin D status and identifies research gaps.

METHODS

A graphical illustration of global vitamin D status was developed based on a systematic review of the worldwide literature published between 1990 and 2011. Studies were eligible if they included samples of randomly selected males and females from the general population and assessed circulating 25-hydroxyvitamin D [25(OH)D] levels. Two different age categories were selected: children and adolescents (1-18 years) and adults (>18 years). Studies were chosen to represent a country based on a hierarchical set of criteria.

RESULTS

In total, 200 studies from 46 countries met the inclusion criteria, most coming from Europe. Forty-two of these studies (21 %) were classified as representative. In children, gaps in data were identified in large parts of Africa, Central and South America, Europe, and most of the Asia/Pacific region. In adults, there was lack of information in Central America, much of South America and Africa. Large regions were identified for which the mean 25(OH)D levels were below 50 nmol/L.

CONCLUSIONS

This study provides an overview of 25(OH)D levels around the globe. It reveals large gaps in information in children and adolescents and smaller but important gaps in adults. In view of the importance of vitamin D to musculoskeletal growth, development, and preservation, and of its potential importance in other tissues, we strongly encourage new research to clearly define 25(OH)D status around the world.

Vitamin D and health in adults in Australia and New Zealand: a position statement

The prevalence of vitamin D deficiency varies, with the groups at greatest risk including housebound, community-dwelling older and/or disabled people, those in residential care, dark-skinned people (particularly those modestly dressed), and other people who regularly avoid sun exposure or work indoors. Most adults are unlikely to obtain more than 5%-10% of their vitamin D requirement from dietary sources. The main source of vitamin D for people residing in Australia and New Zealand is exposure to sunlight. A serum 25-hydroxyvitamin D (25-OHD) level of ≥ 50 nmol/L at the end of winter (10-20 nmol/L higher at the end of summer, to allow for seasonal decrease) is required for optimal musculoskeletal health. Although it is likely that higher serum 25-OHD levels play a role in the prevention of some disease states, there is insufficient evidence from randomised controlled trials to recommend higher targets. For moderately fair-skinned people, a walk with arms exposed for 6-7 minutes mid morning or mid afternoon in summer, and with as much bare skin exposed as feasible for 7-40 minutes (depending on latitude) at noon in winter, on most days, is likely to be helpful in maintaining adequate vitamin D levels in the body. When sun exposure is minimal, vitamin D intake from dietary sources and supplementation of at least 600 IU (15 µg) per day for people aged ≤ 70 years and 800 IU (20 µg) per day for those aged > 70 years is recommended. People in high-risk groups may require higher doses. There is good evidence that vitamin D plus calcium supplementation effectively reduces fractures and falls in older men and women.

Vitamin D intake is inversely related to risk of developing metabolic syndrome in African American and white men and women over 20 y: the Coronary Artery Risk Development in Young Adults study

BACKGROUND

Vitamin D intake may play a key role in the prevention of cardiovascular disease.

OBJECTIVE

We evaluated associations of dietary and supplemental vitamin D intake with the 20-y incidence of metabolic syndrome.

DESIGN

Data from 4727 black and white young men and women from the Coronary Artery Risk Development in Young Adults study were used to examine relations of dietary plus supplemental vitamin D intake with the incidence of metabolic syndrome (as defined by Adult Treatment Panel, third report, guidelines) and the prevalence of its components, including abdominal obesity, elevated blood pressure, and high glucose, low HDL, and high triglyceride concentrations.

RESULTS

The intake of vitamin D from dietary and supplemental sources was inversely related to the 20-y cumulative prevalence of abdominal obesity (P = 0.05) and high glucose (P = 0.02) and low HDL (P = 0.004) concentrations after adjustment for age, sex, race, education, center, and energy intake. In comparison with the lowest intake quintile (quintile 1), HRs (95% CIs) of developing incident metabolic syndrome for quintiles 2-5 of vitamin D intake were 0.82 (0.67, 1.00), 0.84 (0.68, 1.03), 0.70 (0.56, 0.88), and 0.82 (95% CI: 0.65, 1.02), respectively (P-trend = 0.03) after adjustment for demographic and lifestyle factors.

CONCLUSIONS

In young adults, the dietary plus supplemental vitamin D intake was inversely related to the development of incident metabolic syndrome over 20 y of follow-up. These findings support the recommendations of the Dietary Guidelines for Americans to increase intakes of vitamin D-rich foods, such as milk and fish.

Vitamin D insufficiency and chronic diseases: hype and reality

In recent years an increasing number of observational studies have suggested that a low vitamin D status contributes to the development of all sorts of chronic diseases. In reality, however, studies that had been adequately controlled for confounding factors ruled out any link between vitamin D insufficiency and, for example, metabolic disorders, arterial hypertension, multiple sclerosis or cognitive dysfunction. Furthermore, a role of vitamin D insufficiency in autoimmune diseases is evident only in animal models but has not yet been established in humans. In respect to many malignancies, vitamin D insufficiency is only one out of many risk factors and its specific impact on disease incidence has never been assessed. There is convincing evidence, however, that vitamin D insufficiency is a major risk factor for osteoporosis, colorectal and breast cancer as well as for cardiovascular disease and mortality. However, it is debatable that circulating 25-hydroxyvitamin D concentrations of 100-150 nmol l(-1) are required for optimal health outcomes. These are overestimates which would afford to raise vitamin D intake to 4000 IU day(-1). In reality, high doses of vitamin D can cause serious health problems because of the U-shaped dose-response relationships that exist in some cases. Data from large cohort studies clearly indicate that serum 25-(OH)D concentrations around 50 nmol l(-1) are sufficient to minimize the risk of osteoporotic fractures, colorectal and breast cancer, and cardiovascular mortality. The fact that the risk-reducing potential of vitamin D depends on adequate calcium nutrition is widely ignored. I here summarize the evidence that efficient disease prevention does not require intake of more vitamin D and calcium than currently recommended for maintaining optimal bone health.

Serum 25-hydroxyvitamin D3 and body composition in an elderly cohort from Germany: a cross-sectional study

Background

Emerging evidence indicates that there is an association between vitamin D and obesity. The aim of this study was to investigate whether the level of serum 25-hydroxyvitamin D₃ [25(OH)D₃] in the elderly is influenced by parameters of anthropometry and body composition independent of potential confounding lifestyle factors and the level of serum intact parathyroid hormone (iPTH).

Methods

Cross-sectional data of 131 independently living participants (90 women, 41 men; aged 66–96 years) of the longitudinal study on nutrition and health status in senior citizens of Giessen, Germany were analysed. Concentrations of 25(OH)D₃ and iPTH were ascertained by an electrochemiluminescence immunoassay. Body composition was measured by a bioelectrical impedance analysis. We performed univariate and multiple regression analyses to examine the influence of body composition on 25(OH)D₃ with adjustments for age, iPTH and lifestyle factors.

Results

In univariate regression analyses, 25(OH)D₃ was associated with body mass index (BMI), hip circumference and total body fat (TBF) in women, but not in men. Using multiple regression analyses, TBF was shown to be a negative predictor of 25(OH)D₃ levels in women even after controlling for age, lifestyle and iPTH (ß = −0.247; P = 0.016), whereas the associations between BMI, hip circumference and 25(OH)D₃ lost statistical significance after adjusting for iPTH. In men, 25(OH)D₃ was not affected by anthropometric or body composition variables.

Conclusions

The results indicate that 25(OH)D₃ levels are affected by TBF, especially in elderly women, independent of lifestyle factors and iPTH.

Serum vitamin D concentration status and its correlation with early biomarkers of remodeling following acute myocardial infarction

BACKGROUND

Low serum level of vitamin D was shown to be associated with cardiovascular diseases as well as the presence of diabetes, dyslipidemia, and hypertension. Vitamin D deficiency is a global problem, and is an Iranian problem as well. To the best of our knowledge, this was the first study on acute myocardial infarction that evaluates the correlation of vitamin D level with inpatients' outcomes, particularly on the early biomarkers of myocardial remodeling.

METHODS

In a prospective study, patients with acute ST segment elevation myocardial infarction were included. The patients' 25 (OH) D levels were identified and the associations with clinical characteristics, including early remodeling biomarkers and in-hospital outcomes, were investigated.

RESULTS

From the 139 included patients, 80.5% were male. The 25 (OH) deficiency was present in 72.7% of the patients. Hypertension and positive history of cardiovascular drug use were risk factors for the presence of low vitamin D levels (OR = 2.92; CI = 1.34-6.37, P < 0.05) and (OR = 2.36; CI = 1.05-5.29, P < 0.05), respectively. Moreover, a significant positive relationship between the inpatients' survival and the concentration of vitamin D was present (P < 0.001). By performing a multivariate analysis, we found that there was a significant inverse relationship between the level of 25 (OH) D and the level of MMP-9 after 72 h (P = 0.011).

CONCLUSION

The results of our study revealed a significant inverse relationship between serum MMP-9 as a biomarker of early remodeling and the level of 25(OH) D in patients after an acute myocardial infarction. Moreover, low level of vitamin D was associated with patients' mortality in this study.

Influence of age and gender on associations of body mass index with bone mineral density, bone turnover markers and circulating calcium-regulating and bone-active sex hormones

Although it is well known that body mass index (BMI) and bone mineral density (BMD) are positively correlated, the mechanisms by which adiposity reduces the risk of osteoporotic fractures are not fully understood. The present study was initiated to gain deeper insight into the mechanisms underlying the osteoprotective effect of adiposity, and to assess particularly the relevance that BMI-associated changes in circulating hormone levels could have for the build-up of additional bone mineral density. Using data from a previous study on a large cohort of healthy adult Austrians, we analyzed correlations of BMI with (i) BMD at sites in the lumbar spine and hip region, (ii) bone resorption and formation markers, (iii) circulating levels of vitamin D, parathyroid hormone, testosterone and estrogen, and (iv) rates of daily vitamin D and calcium intake. After adjustment for age, positive correlations between BMI and BMD were highly significant (P<0.0001) at all skeletal sites across the entire study cohort. Associations were stronger in post-menopausal women than in pre-menopausal women and in men. In absolute values, the gain in BMD at the lumbar spine from an incremental rise of BMI in post-menopausal women was 1.5-fold higher than in pre-menopausal women, and three times of that observed in men (P<0.05). Inverse relations between BMI and β-crosslaps were consistently found in men (P<0.01) and in women before and after menopause (P<0.01 and P<0.05, respectively), suggesting that inhibition of osteoclastic bone resorption is responsible at least in part for the positive effect of high BMI on BMD. Sub-group analysis revealed that increasing BMI was associated with a significant fall of testosterone in men (P<0.05), and of 25-(OH)D in pre- and post-menopausal women (P<0.001 and P<0.05, respectively), but with a significant rise in PTH (P<0.01) in women before menopause. Since all these hormonal changes would cause bone loss, this excludes their playing any role in the osteoprotective effect of adiposity.