Vitamin D Supplementation Efficacy: Sleeve Gastrectomy Versus Gastric Bypass Surgery

Background

Vitamin D deficiency is common with bariatric surgery, and few prospective studies comparing different surgical procedures have evaluated appropriate vitamin D supplementation levels. Therefore, vitamin D₃ and calcium supplementation were evaluated following gastric bypass and sleeve gastrectomy.

Methods

Women consumed 2,000 international units (IU) of vitamin D₃ and 1,500 mg calcium citrate daily for 3 months following gastric bypass (n?=?11) and sleeve gastrectomy (n?=?12). Height, weight, body mass index (BMI), serum 25-hydroxyvitamin D [25(OH)D], and serum PTH concentrations were measured preoperatively and at 3 months. Wilcoxon signed rank analyses compared body weight parameters, serum 25(OH)D and PTH concentrations, and dietary intakes of vitamin D and calcium preoperatively and at 3 months. Vitamin D deficiency was defined as a serum 25(OH)D concentration <20 ng/mL (50 nmol/L).

Results

Vitamin D deficiency decreased from 60.6 % preoperatively to 26.1 % after 3 months (P?P?Conclusions Reduced food intake increased the risk of vitamin D deficiency following bariatric surgery. However, daily supplementation with 2,000 IU of vitamin D₃ and 1,500 mg calcium citrate significantly increased 25(OH)D concentrations and reduced the percent of women who were vitamin D deficient. Although serum 25(OH)D concentrations did not reach levels associated with detrimental health effects, several women remained vitamin D deficient and more aggressive supplementation may be indicated.     

Vitamin D status in relation to obesity, bone mineral density, bone turnover markers and vitamin D receptor genotypes in healthy Saudi pre- and postmenopausal women

Summary

The various factors that may contribute to vitamin D deficiency or insufficiency were examined among healthy Saudi pre- and postmenopausal women. Vitamin D deficiency was highly prevalent among studied Saudi women with obesity, poor sunlight exposure, poor dietary vitamin D supplementation and age as the main risk factors.

Introduction

The various factors that may contribute to vitamin D deficiency or insufficiency in relation to bone health among Saudi women are not known. The main objectives of the present study were to determine the factors influencing vitamin D status in relation to serum 25-hydroxyvitamin D (25(OH)D), intact parathyroid hormone (PTH), bone turnover markers (BTMs), bone mineral density (BMD), and vitamin D receptor genotype (VDR) in healthy Saudi pre- and postmenopausal women.

Methods

A total number of 1,172 healthy Saudi women living in the Jeddah area were randomly selected and studied. Anthropometric parameters, socioeconomic status, sun exposure index together with serum levels of 25(OH)D, calcitriol, intact PTH, Ca, PO4, Mg, creatinine, albumin, and biochemical BTMs were measured. BMD was measured by a dual energy X-ray absorptiometry and VDR genotypes were also determined.

Results

About 80.0% of Saudi women studied exhibited vitamin D deficiency (serum 25(OH)D?<?50.0?nmol/L) with only 11.8% of all women were considered with adequate vitamin D status (serum 25(OH)D?>?75?nmol/L). Secondary hyperparathyroidism was evident in 18.5% and 24.6% in pre- and postmenopausal women with 25(OH)D?<?50?nmol/L. Serum 25(OH)D was lower (P?<?0.001) and intact PTH higher (P?<?0.001) in the upper quintiles of body mass index (BMI) and waist-to-hip ratio (WHR). Multiple linear regression analysis showed that BMI, sun exposure index, poor dietary vitamin D supplementation, WHR, and age were independent positive predictors of serum 25(OH)D values.

Conclusions

Vitamin D deficiency is highly prevalent among healthy Saudi pre-and postmenopausal women and largely attributed to obesity, poor exposure to sunlight, poor dietary vitamin D supplementation, and age.     

25-Hydroxyvitamin D in Canadian adults: biological, environmental, and behavioral correlates

Summary

We assessed vitamin D status and its correlates in the population-based Canadian Multicentre Osteoporosis Study (CaMos). Results showed that serum 25-hydroxyvitamin D levels <75?nmol/L were common. Given Canada??s high latitude, attention should be given to strategies for enhancing vitamin D status in the population.

Introduction

Inadequate vitamin D has been implicated as a risk factor for several clinical disorders. We assessed, in a Canadian cohort, vitamin D status and its correlates, based on serum 25-hydroxyvitamin D [25(OH)D], the best functional indicator of vitamin D status.

Methods

We studied 577 men and 1,335 women 35+ years from seven cities across Canada in the randomly selected, population-based Canadian Multicentre Osteoporosis Study (CaMos). Participants completed a comprehensive questionnaire. Serum 25(OH)D was measured by immunoassay. Multivariate linear regression modeling assessed the association between 25(OH)D and determinants of vitamin D status.

Results

Participants (2.3%) were deficient in 25(OH)D (<27.5?nmol/L); a further 18.1% exhibited 25(OH)D insufficiency (27.5?C50?nmol/L). Levels <75?nmol/L were evident in 57.5% of men and 60.7% of women and rose to 73.5% in spring (men) and 77.5% in winter (women); 25(OH)D <50?nmol/L was ??10% year round for those supplementing with ??400?IU vitamin D/day but was 43.9% among those not supplementing in winter and spring. The strongest predictors of reduced 25(OH)D for both men and women were winter and spring season, BMI ??30, non-white ethnicity, and lower vitamin D supplementation and its modification by fall and winter.

Conclusions

In this national Canadian cohort, vitamin D levels <75?nmol/L were common, particularly among non-white and obese individuals, and in winter and spring. Vitamin D intake through diet and supplementation and maintenance of normal weight are key modifiable factors for enhancing vitamin D status and thus potentially influencing susceptibility to common chronic diseases.     

Obesity and Association of Serum 25(OH)D Levels with All-Cause Mortality

Sequestration of vitamin D in adipose tissue is the main cause of the lower serum 25(OH)D levels in obese subjects. However, it remains unknown whether the adipose tissue stores of vitamin D are readily mobilized for meeting body needs. We aimed to examine whether the association between serum 25(OH)D and all-cause mortality differs by body weight. Using the computerized database of the largest health care provider in Israel, we identified a cohort of subjects ≥20-years old with serum 25(OH)D levels measured between January 2008 and December 2009. Mortality was ascertained through April-2013. Cox regression with restricted cubic-spline function was used to assess the association between serum 25(OH)D and mortality. Median follow-up was 48 months (IQR 43–53 months); 12,337 of 175,781 participants (7.0 %) died. The association between 25(OH)D and mortality was not linear (P < 0.001), and differed between BMI categories (P = 0.019). The lowest adjusted risk for mortality was observed at serum 25(OH)D levels of 73.0, 68.0, and 66.5 nmol/L among subjects with BMI <25, 25–29.9, and ≥30 kg/m², respectively. Compared to reference level of 75 nmol/L, increased adjusted HR as evident by 95 % confidence interval lower bound >1.0 was observed at serum 25(OH)D levels less than; 61.0, 48.0, and 40.0 nmol/L among subjects with BMI <25, 25–29.9, and ≥30 kg/m², respectively. Serum 25(OH)D levels associated with increased all-cause mortality were inversely related to BMI. However, this observational cohort study may still suffer from residual confounding; therefore, cause and effect relationship cannot be established from this study.     

Longitudinal changes and seasonal variations in serum 25-hydroxyvitamin D levels in different age groups: results of the Longitudinal Aging Study Amsterdam

Summary

Vitamin D levels remained fairly stable during ageing with increasing levels in persons aged 55–65 years old and decreasing levels in persons aged 65–88 years old. The seasonal variation was larger than the longitudinal change. Our findings implicate that vitamin D supplementation becomes more important in older age groups and during wintertime.

Introduction

Longitudinal changes in serum 25-hydroxyvitamin D (25-OHD) levels during aging have not been studied extensively. Two studies showed increasing serum 25-OHD levels. One of these studies suggested that there might be decreasing levels in persons aged 65 years and older. The objectives of the current study are the following: (1) to examine longitudinal changes in serum 25-OHD levels in different age groups and (2) to describe the seasonal variation in different age groups.

Methods

Data of the Longitudinal Aging Study Amsterdam (LASA), an ongoing cohort study, were used. Two different cohorts were included: (1) younger cohort: aged 55–65 years old at baseline, n?=?738, follow-up of 6 years and (2) older cohort: aged 65–88 years old at baseline, n?=?1,320, follow-up of 13 years.

Results

At baseline, average levels were 56.5 nmol/L in the younger cohort and 51.1 nmol/L in the older cohort. In the younger cohort, a longitudinal increase in the mean serum 25-OHD levels of 4 nmol/L in 6 years was observed; in the older cohort, a longitudinal decrease in the mean serum 25-OHD levels of 4 nmol/L in 13 years was observed. The seasonal variation was ±12 nmol/L in the younger cohort and ±7 nmol/L in the older cohort.

Conclusions

Long-term serum 25-OHD levels remained fairly stable during aging with slightly increasing levels in persons aged 55–65 years old and slightly decreasing levels in persons aged 65–88 years old. On average, the seasonal variation was larger than the longitudinal change. Our findings implicate that vitamin D supplementation becomes more important in older age groups and during wintertime.     

Vitamin D deficiency in UK South Asian Women of childbearing age: a comparative longitudinal investigation with UK Caucasian women

Summary

This is the first 1-year longitudinal study which assesses vitamin D deficiency in young UK-dwelling South Asian women. The findings are that vitamin D deficiency is extremely common in this group of women and that it persists all year around, representing a significant public health concern.

Introduction

There is a lack of longitudinal data assessing seasonal variation in vitamin D status in young South Asian women living in northern latitudes. Studies of postmenopausal South Asian women suggest a lack of seasonal change in 25-hydroxy vitamin D [25(OH)D], although it is unclear whether this is prevalent among premenopausal South Asians. We aimed to evaluate, longitudinally, seasonal changes in 25(OH)D and prevalence of vitamin D deficiency in young UK-dwelling South Asian women as compared with Caucasians. We also aimed to establish the relative contributions of dietary vitamin D and sun exposure in explaining serum 25(OH)D.

Methods

This is a 1-year prospective cohort study assessing South Asian (n?=?35) and Caucasian (n?=?105) premenopausal women living in Surrey, UK (51° N), aged 20–55 years. The main outcome measured was serum 25(OH)D concentration. Secondary outcomes were serum parathyroid hormone, self-reported dietary vitamin D intake and UVB exposure by personal dosimetry.

Results

Serum 25(OH)D?<25 nmol/L was highly prevalent in South Asians in the winter (81 %) and autumn (79.2 %). Deficient status (below 50 nmol/L) was common in Caucasian women. Multi-level modelling suggested that, in comparison to sun exposure (1.59, 95 %CI?=?0.83–2.35), dietary intake of vitamin D had no impact on 25(OH)D levels (?0.08, 95 %CI?=??1.39 to 1.23).

Conclusions

Year-round vitamin D deficiency was extremely common in South Asian women. These findings pose great health threats regarding the adverse effects of vitamin D deficiency in pregnancy and warrant urgent vitamin D public health policy and action.     

Vitamin D status of schoolchildren in Northern Algeria,seasonal variations and determinants of vitamin D deficiency

Summary

There are no published data on the vitamin D status of children living in North Africa. In 435 healthy Algerian children 5–15 years old, we found that vitamin D insufficiency (serum 25-hydroxyvitamin D (25OHD) <50 nmol/L) was frequent, especially in winter. Low vitamin D status was associated with increased parathyroid hormone (PTH) and leg deformation

Introduction

As there are no published data on the vitamin D status of children living in North Africa, we evaluated the 25OHD concentration of healthy Algerian children at the end of summer and at the end of winter. As secondary objectives, we studied the various determinants of vitamin D status and the PTH-25OHD relationship in these subjects.

Methods

Four hundred thirty-five children 5–15 years old were examined and had a blood sample in September 2010. Of them, 408 were sampled again in March 2011.

Results

Median 25OHD concentration in the whole group was 71.4 nmol/L in September and 52.9 nmol/L in March. In September, 58.4, 29.9, and 8.1 % had a 25OHD concentration below 75, 50, and 30 nmol/L respectively. In March, these percentages increased to 65.2, 41.4, and 17.4 % for the 75, 50, and 30 nmol/L threshold, respectively. In multivariate analysis, older age, darker skin phototype, low daily vitamin D and calcium intake, poor socioeconomic status, and short daily sun exposure remained significantly associated with a 25OHD <50 nmol/L at both visits. In 72 (16.6 %) children, genu varum/valgum was present. Compared to the 363 children without leg deformation, they presented more frequently with the risk factors of vitamin D insufficiency. They also had lower 25OHD concentrations and higher PTH and tALP. Serum PTH and 25OHD concentrations were negatively and significantly correlated (r?=??0.43; p?<?0.001) without a 25OHD threshold above which PTH does not decrease anymore.

Conclusion

Despite a sunny environment, vitamin D insufficiency is frequent in healthy Algerian children.     

Ethnic differences in 25-hydroxyvitamin D levels and response to treatment in CKD

Aim

Nutritional vitamin D [25(OH)D] deficiency is common in patients with chronic kidney disease (CKD). No studies have specifically examined the differences between ethnic groups in response to ergocalciferol (“D2”) therapy.

Methods

A retrospective analysis was performed to evaluate the effectiveness of D2 therapy as recommended by the KDOQI guidelines in 184 Hispanic and Caucasian nondialysis CKD patients.

Results

Low 25(OH)D levels (<75 nmol/L) were found in 89.4 % of Hispanics versus 61.4 % of Caucasians, despite similar degrees of CKD. Treatment per KDOQI guidelines resulted in 85.5 % of treated Hispanics and 66.7 % of treated Caucasians remaining vitamin D-deficient. Although both Hispanics and Caucasians had significant (P < 0.0001) changes in 25(OH)D levels, absolute changes were modest (12.5 ± 2.0 nmol/mL in Hispanics, 20.0 ± 3.5 nmol/L in Caucasians). The increase seen in Caucasians was significantly greater than in Hispanics (P < 0.0001). In multiple logistic regression modeling, Hispanic ethnicity remained independently associated with poorer response to therapy (P = 0.0055), even after adjustment for other factors.

Conclusions

While both Hispanics and Caucasians demonstrated suboptimal response to the KDOQI-guided vitamin D repletion strategy, Hispanic ethnicity was significantly associated with poorer response. Our findings may have implications for other darker-skinned populations, even in solar-rich environments.     

Serum 25-Hydroxyvitamin D in Obese Spanish Adults: the Camargo Cohort Study

Objectives

To describe the 25(OH)D status in Spanish obese postmenopausal women and men ≥?50 years, to compare their results with those of the overweight or normal weight population, and to determine whether differences are observed between both sexes and with seasonal variation throughout the year.

Patients and Methods

We studied 2597 subjects (1826 postmenopausal women and 771 men ≥?50 years). Serum concentrations of 25(OH)D, intact parathyroid hormone (PTH), aminoterminal propeptide of type I collagen (PINP), and C-terminal telopeptide of type I collagen (CTX) were determined by electrochemiluminiscence (Elecsys 2010, Roche). Bone mineral density (BMD) was measured by DXA. Participants were divided according to body mass index (BMI) groups (normal ≥?20 and <?25 kg/m², overweight ≥?25 and?<?30 kg/m², or obese ≥?30 kg/m²).

Results

Obese people had lower serum 25(OH)D values (20.9?±?8.2 ng/ml) than overweight (23.3?±?8.8 ng/ml; p?<?0.0001) or normal-weight subjects (24.4?±?8.9 ng/ml; p?<?0.0001). They have also lower levels of both PINP and CTX. In contrast, PTH concentrations and BDM values were higher in obese individuals. When stratifying by sex, the difference in serum concentration of 25(OH)D remained significant in women, but not in men, persisted throughout the year, and was inversely correlated with BMI and waist circumference.

Conclusions

Despite lower serum 25(OH)D concentrations and higher PTH levels, obese and overweight women have higher lumbar spine and hip BMD and lower bone remodeling markers than normal weight women, suggesting that low serum 25(OH)D levels do not negatively affect bone health.

     

Vitamin D status and parathyroid hormone relationship in adolescents and its association with bone health parameters: analysis of the Northern Ireland Young Heart’s Project

Summary

In girls, a plateau in parathyroid hormone (PTH) was observed at a 25-hydroxyvitamin D (25(OH)D) concentration of approximately 60 nmol/l. In boys, there was no plateau in PTH concentrations as 25(OH)D concentration increased. A 25(OH)D threshold of 60 nmol/l appears to have implications for bone health outcomes in both girls and boys.

Introduction

Our objective was to investigate if there is a threshold 25(OH)D concentration where a plateau in PTH concentration is evident and to examine the impact of this relationship on bone mineral density (BMD) and bone turnover in a representative sample of adolescents.

Methods

We conducted a cross-sectional analysis among 1,015 Northern Irish adolescents aged 12 and 15 years. Serum 25(OH)D, PTH, osteocalcin, type 1 collagen cross-linked C-telopeptide (CTx), and BMD of the nondominant forearm and heel were measured. Nonlinear regression analysis was used to model the association between 25(OH)D and PTH.

Results

In girls, a plateau in PTH was observed at a 25(OH)D concentration of approximately 60 nmol/l (PTH?=?47.146?+?370.314?×?exp^{(?0.092?×?25(OH)D)}) while no plateau in PTH was observed in boys (PTH?=?42.144?+?56.366?×?exp^{(?0.022?×?25(OH)D)}). Subjects with 25(OH)D levels <60 nmol/l had significantly higher osteocalcin concentrations (P?<?0.05) compared with those who had ≥60 nmol/l, while no significant (P?>?0.05) differences were noted for CTx concentrations. In girls only, nondominant forearm BMD but not heel BMD was significantly higher (P?=?0.046) in those with 25(OH)D concentrations?≥?60 nmol/l.

Conclusions

Serum 25(OH)D levels above 60 nmol/l in Northern Irish adolescent girls prevent an increase in serum PTH levels and maintaining 25(OH)D >60 nmol/l in both girls and boys may lead to improved bone health outcomes.     

Prospective evaluation of renal function,serum vitamin D level,and risk of fall and fracture in community-dwelling elderly subjects

Summary

This prospective study in elderly showed that kidney function plays a minor role in explaining the high prevalence of vitamin D deficiency seen in noninstitutionalized elderly subjects. However, 25-hydroxyvitamin D levels were clearly inversely associated with risk for first fall, which was especially seen in subjects with calcium levels above median.

Introduction

Few prospective studies in elderly exist that have investigated the association of renal dysfunction and vitamin D status on risk of falls. The aim of this study is to evaluate the association of renal function with 25-hydroxyvitamin D (25-OH-D) levels and, secondly, to assess the role of both factors on the risk of falls and subsequent bone fractures.

Methods

This is a prospective population-based cohort study among noninstitutionalized elderly subjects during a 1-year follow-up. 25-OH-D levels and renal function were estimated, the latter by cystatin C-based equations. Information on falls was assessed prospectively.

Results

Overall, 1,385 subjects aged 65 and older were included in the study (mean age 75.6 years), of whom 9.2 % had a 25-OH-D serum level above 75 nmol/L (US units 30 ng/mL); 41.4 %, between 50 and 75 nmol/L (US units 20 to 29 ng/mL, insufficiency); and 49.4 %, <50 nmol/L (US units <20 ng/mL, deficiency). We found no association of chronic kidney disease with risk of first fall. In contrast, 25-OH-D serum categories were clearly associated with risk of first fall and we found evidence of effect modification with calcium levels. In the group with a calcium level above the median (≥9.6 mg/dL), subjects with 25-OH-D serum level between 50 and 75 nmol/L and with concentrations <50 nmol/L had a hazard rate ratio (HRR) of 1.75 (1.03–2.87) and 1.93 (1.10–3.37) for risk of first fall. 25-OH-D serum levels were also associated with several markers of inflammation and hemodynamic stress.

Conclusions

We demonstrated an association of 25-OH-D serum levels and risk of first fall, which was especially evident in subjects with serum calcium in upper normal, independent of renal function.     

Non-linear relationship between serum 25-hydroxyvitamin D concentration and subsequent hip fracture

Summary

Serum 25-OH vitamin D levels were compared in 254 hip fracture subjects and 2,402 matched control subjects. There was a significant inverse association between 25-OH vitamin D and hip fracture only between 0 and 70 nmol/L.

Introduction

Vitamin D is integral to bone metabolism, however the utility of serum 25-OH vitamin D as a risk marker for hip fractures is controversial.

Methods

We conducted a case–control study of patients admitted to the hospitals with hip fractures in Calgary, Alberta, (catchment population 1.4 million) between January 1, 2007 and August 31, 2011. We searched the laboratory information system of Calgary Laboratory Services for serum 25-OH vitamin D levels within 6 months prior to admission on patients admitted to hospital with hip fractures. Cases were identified through the Calgary Laboratory Services laboratory information system and were matched to controls for age, sex, and month of testing. The hip fracture–25-OH vitamin D association was examined using multiple linear and spline regression.

Results

Of 305 subjects initially identified with hip fractures, serum 25-OH vitamin D levels were available for 254 (83 %). These were matched to 2,402 control subjects. We observed a significant (p?<?0.01) non-linear relationship such that 25-OH vitamin D was inversely associated with hip fracture only below 70 nmol/L (odds ratio?=?0.81 per 10 nmol/L increase; 95 % CI 0.86–0.93).

Conclusions

The utility of 25-OH vitamin D level as a risk marker for hip fracture depends on the cut-off level used and was of potential use only for lower levels of 25-OH vitamin D.     

Vitamin D status is associated with physical performance: the results of three independent cohorts

Summary

This study, on the association between vitamin D status and physical performance and its decline, shows that vitamin D status is associated with physical performance in several older age groups. However, vitamin D status does not predict a decline in physical performance in individuals aged 55–65 years.

Introduction

Previous research in the Longitudinal Aging Study Amsterdam (LASA) showed an association of vitamin D status with physical performance and its decline in persons aged 65 years and older. The current study aims to determine these associations in younger individuals and to replicate previous research of LASA.

Methods

Data from three independent cohorts were used: two cohorts of LASA (LASA-II with measurements in 2002 (n?=?707) and 2009 (n?=?491), LASA-I-2009 (n?=?355)) and the baseline measurement of the B-Vitamins for the Prevention of Osteoporotic Fractures (B-PROOF) study (n?=?2,813). Participants performed three tests (walking test, chair stands, and tandem stand; range total score 0–12), except in LASA-II-2002 (only walking and chair stands tests; range total score 0–8). Multiple linear and logistic regression were used to assess whether vitamin D status was associated with total physical performance and its decline, respectively.

Results

The mean age of the participants was 60.0 (SD 3.0), 65.9 (2.9), 78.4 (5.3), and 74.4 (6.8) years for LASA-II-2002, LASA-II-2009, LASA-I-2009, and B-PROOF, respectively. Vitamin D status was not predictive of a clinical decline in total physical performance score in the LASA-II-2002 cohort (aged 55–65 years). After adjustment for confounding, participants with serum 25(OH)D?<?50 nmol/L scored 0.8 (95 % confidence interval 0.4–1.2), 0.9 (0.3–1.5), 1.5 (0.8–2.3), and 0.6 (0.3–0.9) points lower on total physical performance than participants with serum 25(OH)D?≥?75 nmol/L.

Conclusion

Our study confirmed that serum 25(OH)D is associated with physical performance. However, vitamin D status did not predict a clinical decline in physical performance in individuals aged 55–65 years.     

Correlation between 25-hydroxyvitamin D levels and latitude in Brazilian postmenopausal women: from the Arzoxifene Generations Trial

Summary

We investigated vitamin D status in Brazilian cities located at different latitudes. Insufficiency (<50 nmol/L) was common (17 %), even in those living in a tropical climate. Vitamin D insufficiency increased as a function of latitude. Mean 25-hydroxyvitamin D (25(OH)D) levels in each site and latitude correlation were very high (r?=??0.88; p?<?0.0001).

Introduction

Inadequate vitamin D, determined by low levels of 25(OH)D, has become very common despite the availability of sunlight at some latitudes. National data from a country that spans a wide range of latitudes would help to determine to what extent latitude or other factors are responsible for vitamin D deficiency. We investigated vitamin D status in cities located at different latitudes in Brazil, a large continental country.

Methods

The source is the Brazilian database from the Generations Trial (1,933 osteopenic or osteoporotic postmenopausal women (60 to 85 years old) with 25(OH)D measurements). 25(OH)D below 25 nmol/L (10 ng/mL) was an exclusion criterion. Baseline values were between fall and winter. The sites included Recife, Salvador, Rio de Janeiro, São Paulo, Curitiba, and Porto Alegre. Mean and standard deviation of 25(OH)D, age, spine and femoral neck T-score, calcium, creatinine, and alkaline phosphatase were calculated for each city. Pearson correlation was used for 25(OH)D and latitude.

Results

Insufficiency (<50 or <20 ng/mL) was common (329 subjects, 17 %). Vitamin D insufficiency increased as a function of latitude, reaching 24.5 % in the southernmost city, Porto Alegre. The correlation between mean 25(OH)D levels in each site and latitude was very high (r?=??0.88, p?<?0.0001).

Conclusion

There is a high percentage of individuals with vitamin D insufficiency in Brazil, even in cities near the equator, and this percentage progressively increases with more southern latitudes.     

A parallel group double-blind RCT of vitamin D3 assessing physical function: is the biochemical response to treatment affected by overweight and obesity?

Summary

Vitamin D may affect skeletal muscle function. In a double-blind, randomised, placebo-controlled trial, we found that vitamin D₃ supplementation (400 or 1,000 I.U. vs. placebo daily for 1 year with bimonthly study visits) does not improve grip strength or reduce falls.

Introduction

This study aimed to test the supplementation effects of vitamin D₃ on physical function and examine associations between overweight/obesity and the biochemical response to treatment.

Methods

In a parallel group double-blind RCT, healthy postmenopausal women from North East Scotland (latitude—57° N) aged 60–70 years (body mass index (BMI), 18–45 kg/m²) were assigned (computer randomisation) to daily vitamin D₃ (400 I.U. (n?=?102)/1,000 I.U. (n?=?101)) or matching placebo (n?=?102) (97, 96 and 100 participants analysed for outcomes, respectively) from identical coded containers for 1 year. Grip strength (primary outcome), falls, diet, physical activity and ultraviolet B radiation exposure were measured bimonthly, as were serum 25(OH)D, adjusted calcium (ACa) and phosphate. Fat/lean mass (dual energy X-ray absorptiometry), anthropometry, 1,25-dihydroxyvitamin D and parathyroid hormone were measured at baseline and 12 months. Participants and researchers were blinded throughout intervention and analysis.

Results

Treatment had no effect on grip strength (mean change (SD)/year?=??0.5 (2.5), ?0.9 (2.7) and ?0.4 (3.3)?kg force for 400/1,000 I.U. vitamin D₃ and placebo groups, respectively (P?=?.10, ANOVA)) or falls (P?=?.65, chi-squared test). Biochemical responses were similar across BMI categories (<25.25–29.99, ≥30 kg/m²) with the exception of a small change at 12-months in serum ACa in overweight compared to non-overweight participants (P?=?.01, ANOVA; 1,000 I.U. group). In the placebo group, 25(OH)D peak concentration change (winter to summer) was negatively associated with weight (r?=??.268), BMI (r?=??.198), total (r?=??.278) and trunk fat mass (r?=??.251), with total and trunk fat mass predictive of winter to summer 25(OH)D change (P?=?.01/.004 respectively, linear regression).

Conclusion

We found no evidence of an improvement in physical function following vitamin D₃ supplementation for 1 year.     

Correction of preoperative vitamin D deficiency after Roux-en-Y gastric bypass surgery

BackgroundTo evaluate the adequacy of supplementation to correct preoperative vitamin D deficiency in adult patients during the year after Roux-en-Y gastric bypass (RYGB) surgery.MethodsThe medical records were reviewed and the preoperative and 12-month postoperative serum 25-hydroxyvitamin D [25(OH)D] levels were compared in patients who underwent RYGB from 2002 to 2004. The serum 25(OH)D levels were defined as being optimal (≥80 nmol/L), suboptimal (50–79 nmol/L), or deficient (<50 nmol/L). Patients with deficient 25(OH)D levels were prescribed 50,000 IU ergocalciferol weekly. The remaining patients averaged 710 IU supplemental vitamin D intake daily.ResultsThe mean patient age was 43.8 ± 10.7 years, and the mean preoperative body mass index was 51.8 ± 9.8 kg/m². Of the 95 patients with baseline and 12-month 25(OH)D levels, 89% were women. The mean preoperative 25(OH)D level was 49.7 ± 26.5 nmol/L; 34% had suboptimal 25(OH)D levels and 54% had deficient levels before surgery. Twelve months after surgery, those receiving 50,000 IU weekly (n = 40) had a mean 25(OH)D level of 69.2 ± 22.2 nmol/L; 63% had suboptimal and 8% deficient levels. Those taking 710 IU daily (n = 55) had a mean 25(OH)D level of 85.5 ± 33.0 nmol/L; 44% had suboptimal and 6% deficient levels.ConclusionVitamin D deficiency is prevalent in RYGB patients before surgery. The vitamin D status improved markedly after RYGB surgery with either 710 IU vitamin D daily or 50,000 IU weekly. Current supplementation practices do not appear to optimize the serum 25(OH)D levels and need to be more closely examined.     

Calcium and vitamin D intake maintained from preovariectomy independently affect calcium metabolism and bone properties in Sprague Dawley rats

Summary

The interaction of habitual Ca and vitamin D intake from preovariectomy to 4 months postovariectomy on bone and Ca metabolism was assessed. Higher Ca intake suppressed net bone turnover, and both nutrients independently benefitted trabecular structure. Habitual intake of adequate Ca and ~50 nmol/L vitamin D status is most beneficial.

Introduction

Dietary strategies to benefit bone are typically tested prior to or after menopause but not through menopause transition. We investigated the interaction of Ca and vitamin D status on Ca absorption, bone remodeling, Ca kinetics, and bone strength as rats transitioned through estrogen deficiency.

Methods

Sprague Dawley rats were randomized at 8 weeks to 0.2 or 1.0 % Ca and 50, 100, or 1,000 IU (1.25, 2.5, or 25 μg) vitamin D/kg diet (2?×?3 factorial design) and ovariectomized at 12 weeks. Urinary ⁴⁵Ca excretion from deep-labeled bone was used to assess net bone turnover weekly. Ca kinetics was performed between 25 and 28 weeks. Rats were killed at 29 weeks. Femoral and tibiae structure (by μCT), dynamic histomorphometry, and bone Ca content were assessed.

Results

Mean 25(OH)D for rats on the 50, 100, 1,000 IU vitamin D/kg diet were 32, 54, and 175 nmol/L, respectively. Higher Ca intake ameliorated net bone turnover, reduced fractional Ca absorption and bone resorption, and increased net Ca absorption. Tibial and femoral trabecular structures were enhanced independently by higher Ca and vitamin D intake. Tibial bone width and fracture resistance were enhanced by higher vitamin D intake. Dynamic histomorphometry in the tibia was not affected by either nutrient. A Ca × vitamin D interaction existed in femur length, tibial Ca content, and mass of the soft tissue/extracellular fluid compartment.

Conclusions

Adequate Ca intake and serum 25(OH)D level of 50 nmol/L provided the most benefit for bone health, mostly through independent effects of Ca and vitamin D.     

Global vitamin D status and determinants of hypovitaminosis D

Summary

This review describes the vitamin D status in different regions of the world with the objective of understanding the scope of hypovitaminosis D and the factors related to its prevalence that may contribute to the pathogenesis of osteoporosis and fragility fractures.

Introduction

Vitamin D status has been linked to the pathogenesis of hip fractures as well as other skeletal and non-skeletal disorders. The purpose of this review is to provide a global perspective of vitamin D status across different regions of the world and to identify the common and significant determinants of hypovitaminosis D.

Methods

Six regions of the world were reviewed—Asia, Europe, Middle East and Africa, Latin America, North America, and Oceania—through a survey of published literature.

Results

The definition of vitamin D insufficiency and deficiency, as well as assay methodology for 25-hydroxyvitamin D or 25(OH)D, vary between studies. However, serum 25(OH)D levels below 75 nmol/L are prevalent in every region studied whilst levels below 25 nmol/L are most common in regions such as South Asia and the Middle East. Older age, female sex, higher latitude, winter season, darker skin pigmentation, less sunlight exposure, dietary habits, and absence of vitamin D fortification are the main factors that are significantly associated with lower 25(OH)D levels.

Conclusion

Reports from across the world indicate that hypovitaminosis D is widespread and is re-emerging as a major health problem globally.     

Low serum 25-hydroxyvitamin D is associated with increased risk of stress fracture during Royal Marine recruit training

Summary

The aim of this study was to investigate vitamin D status and stress fracture risk during Royal Marine military training. Poor vitamin D status was associated with an increased risk of stress fracture. Vitamin D supplementation may help to reduce stress fracture risk in male military recruits with low vitamin D status.

Introduction

Stress fracture is a common overuse injury in military recruits, including Royal Marine (RM) training in the UK. RM training is recognised as one of the most arduous basic training programmes in the world. Associations have been reported between serum 25-hydroxyvitamin D (25(OH)D) and risk of stress fracture, but the threshold of 25(OH)D for this effect remains unclear. We aimed to determine if serum 25(OH)D concentrations were associated with stress fracture risk during RM training.

Methods

We prospectively followed 1082 RM recruits (males aged 16–32 years) through the 32-week RM training programme. Troops started training between September and July. Height, body weight and aerobic fitness were assessed at week 1. Venous blood samples were drawn at weeks 1, 15 and 32. Serum samples were analysed for 25(OH)D and parathyroid hormone (PTH).

Results

Seventy-eight recruits (7.2 %) suffered a total of 92 stress fractures. Recruits with a baseline serum 25(OH)D concentration below 50 nmol L^?1 had a higher incidence of stress fracture than recruits with 25(OH)D concentration above this threshold (χ² ₍₁₎?=?3.564, p?=?0.042; odds ratio 1.6 (95 % confidence interval (CI) 1.0–2.6)). Baseline serum 25(OH)D varied from 47.0?±?23.7 nmol L^?1 in February, to 97.3?±?24.6 nmol L^?1 in July (overall mean 69.2?±?29.2 nmol L^?1, n?=?1016). There were weak inverse correlations between serum 25(OH)D and PTH concentrations at week 15 (r?=??0.209, p?<?0.001) and week 32 (r?=??0.214, p?<?0.001), but not at baseline.

Conclusion

Baseline serum 25(OH)D concentration below 50 nmol L^?1 was associated with an increased risk of stress fracture. Further studies into the effects of vitamin D supplementation on stress fracture risk are certainly warranted.