Karin M. A. Swart

Vitamin D deficiency in Europe: pandemic?

Background: Vitamin D deficiency has been described as being pandemic, but serum 25-hydroxyvitamin D [25(OH)D] distribution data for the European Union are of very variable quality. The NIH-led international Vitamin D Standardization Program (VDSP) has developed protocols for standardizing existing 25(OH)D values from national health/nutrition surveys. Objective: This study applied VDSP protocols to serum 25(OH)D data from representative childhood/teenage and adult/older adult European populations, representing a sizable geographical footprint, to better quantify the prevalence of vitamin D deficiency in Europe. Design: The VDSP protocols were applied in 14 population studies [reanalysis of subsets of serum 25(OH)D in 11 studies and complete analysis of all samples from 3 studies that had not previously measured it] by using certified liquid chromatography–tandem mass spectrometry on biobanked sera. These data were combined with standardized serum 25(OH)D data from 4 previously standardized studies (for a total n = 55,844). Prevalence estimates of vitamin D deficiency [using various serum 25(OH)D thresholds] were generated on the basis of standardized 25(OH)D data. Results: An overall pooled estimate, irrespective of age group, ethnic mix, and latitude of study populations, showed that 13.0% of the 55,844 European individuals had serum 25(OH)D concentrations <30 nmol/L on average in the year, with 17.7% and 8.3% in those sampled during the extended winter (October–March) and summer (April–November) periods, respectively. According to an alternate suggested definition of vitamin D deficiency (<50 nmol/L), the prevalence was 40.4%. Dark-skinned ethnic subgroups had much higher (3- to 71-fold) prevalence of serum 25(OH)D <30 nmol/L than did white populations. Conclusions: Vitamin D deficiency is evident throughout the European population at prevalence rates that are concerning and that require action from a public health perspective. What direction these strategies take will depend on European policy but should aim to ensure vitamin D intakes that are protective against vitamin D deficiency in the majority of the European population.

Rationale and design of the B-PROOF study, a randomized controlled trial on the effect of supplemental intake of vitamin B12 and folic acid on fracture incidence

BackgroundOsteoporosis is a major health problem, and the economic burden is expected to rise due to an increase in life expectancy throughout the world. Current observational evidence suggests that an elevated homocysteine concentration and poor vitamin B12 and folate status are associated with an increased fracture risk. As vitamin B12 and folate intake and status play a large role in homocysteine metabolism, it is hypothesized that supplementation with these B-vitamins will reduce fracture incidence in elderly people with an elevated homocysteine concentration.Methods/DesignThe B-PROOF (B-Vitamins for the PRevention Of Osteoporotic Fractures) study is a randomized double-blind placebo-controlled trial. The intervention comprises a period of two years, and includes 2919 subjects, aged 65 years and older, independently living or institutionalized, with an elevated homocysteine concentration (≥ 12 μmol/L). One group receives daily a tablet with 500 μg vitamin B12 and 400 μg folic acid and the other group receives a placebo tablet. In both tablets 15 μg (600 IU) vitamin D is included. The primary outcome of the study is osteoporotic fractures. Measurements are performed at baseline and after two years and cover bone health i.e. bone mineral density and bone turnover markers, physical performance and physical activity including falls, nutritional intake and status, cognitive function, depression, genetics and quality of life. This large multi-center project is carried out by a consortium from the Erasmus MC (Rotterdam, the Netherlands), VUmc (Amsterdam, the Netherlands) and Wageningen University, (Wageningen, the Netherlands), the latter acting as coordinator.DiscussionTo our best knowledge, the B-PROOF study is the first intervention study in which the effect of vitamin B12 and folic acid supplementation on osteoporotic fractures is studied in a general elderly population. We expect the first longitudinal results of the B-PROOF intervention in the second semester of 2013. The results of this intervention will provide evidence on the efficacy of vitamin B12 and folate supplementation in the prevention of osteoporotic fractures.Trial RegistrationThe B-PROOF study is registered with the Netherlands Trial (NTR NTR1333) and with ClinicalTrials.gov (NCT00696514).

Vitamin D and mortality: Individual participant data meta-analysis of standardized 25-hydroxyvitamin D in 26916 individuals from a European consortium

Background Vitamin D deficiency may be a risk factor for mortality but previous meta-analyses lacked standardization of laboratory methods for 25-hydroxyvitamin D (25[OH]D) concentrations and used aggregate data instead of individual participant data (IPD). We therefore performed an IPD meta-analysis on the association between standardized serum 25(OH)D and mortality. Methods In a European consortium of eight prospective studies, including seven general population cohorts, we used the Vitamin D Standardization Program (VDSP) protocols to standardize 25(OH)D data. Meta-analyses using a one step procedure on IPD were performed to study associations of 25(OH)D with all-cause mortality as the primary outcome, and with cardiovascular and cancer mortality as secondary outcomes. This meta-analysis is registered at ClinicalTrials.gov, number NCT02438488. Findings We analysed 26916 study participants (median age 61.6 years, 58% females) with a median 25(OH)D concentration of 53.8 nmol/L. During a median follow-up time of 10.5 years, 6802 persons died. Compared to participants with 25(OH)D concentrations of 75 to 99.99 nmol/L, the adjusted hazard ratios (with 95% confidence interval) for mortality in the 25(OH)D groups with 40 to 49.99, 30 to 39.99, and <30 nmol/L were 1.15 (1.00–1.29), 1.33 (1.16–1.51), and 1.67 (1.44–1.89), respectively. We observed similar results for cardiovascular mortality, but there was no significant linear association between 25(OH)D and cancer mortality. There was also no significantly increased mortality risk at high 25(OH)D levels up to 125 nmol/L. Interpretation In the first IPD meta-analysis using standardized measurements of 25(OH)D we observed an association between low 25(OH)D and increased risk of all-cause mortality. It is of public health interest to evaluate whether treatment of vitamin D deficiency prevents premature deaths.

Effect of daily vitamin B-12 and folic acid supplementation on fracture incidence in elderly individuals with an elevated plasma homocysteine concentration: B-PROOF, a randomized controlled trial

BACKGROUND Elevated plasma homocysteine concentrations are a risk factor for osteoporotic fractures. Lowering homocysteine with combined vitamin B-12 and folic acid supplementation may reduce fracture risk. OBJECTIVE This study [B-vitamins for the PRevention Of Osteoporotic Fractures (B-PROOF)] aimed to determine whether vitamin B-12 and folic acid supplementation reduces osteoporotic fracture incidence in hyperhomocysteinemic elderly individuals. DESIGN This was a double-blind, randomized, placebo-controlled trial in 2919 participants aged ≥65 y with elevated homocysteine concentrations (12-50 μmol/L). Participants were assigned to receive daily 500 μg vitamin B-12 plus 400 μg folic acid or placebo supplementation for 2 y. Both intervention and placebo tablets also contained 600 IU vitamin D3. The primary endpoint was time to first osteoporotic fracture. Exploratory prespecified subgroup analyses were performed in men and women and in individuals younger than and older than age 80 y. Data were analyzed according to intention-to-treat and per-protocol principles. RESULTS Osteoporotic fractures occurred in 61 persons (4.2%) in the intervention group and 75 persons (5.1%) in the placebo group. Osteoporotic fracture risk was not significantly different between groups in the intention-to-treat analyses (HR: 0.84; 95% CI: 0.58, 1.21) or per-protocol analyses (HR: 0.81; 95% CI: 0.54, 1.21). For persons aged >80 y, in per-protocol analyses, osteoporotic fracture risk was lower in the intervention group than in the placebo group (HR: 0.27; 95% CI: 0.10, 0.74). The total number of adverse events (including mortality) did not differ between groups. However, 63 and 42 participants in the intervention and placebo groups, respectively, reported incident cancer (HR: 1.56; 95% CI: 1.04, 2.31). CONCLUSIONS These data show that combined vitamin B-12 and folic acid supplementation had no effect on osteoporotic fracture incidence in this elderly population. Exploratory subgroup analyses suggest a beneficial effect on osteoporotic fracture prevention in compliant persons aged >80 y. However, treatment was also associated with increased incidence of cancer, although the study was not designed for assessing cancer outcomes. Therefore, vitamin B-12 plus folic acid supplementation cannot be recommended at present for fracture prevention in elderly people. The B-PROOF study was registered with the Netherlands Trial Register (trialregister.nl) as NTR1333 and at clinicaltrials.gov as NCT00696414.

Results of 2-year vitamin B treatment on cognitive performance; Secondary data from an RCT

Objective: We investigated the effects of 2-year folic acid and vitamin B12 supplementation on cognitive performance in elderly people with elevated homocysteine (Hcy) levels. Methods: This multicenter, double-blind, randomized, placebo-controlled trial included 2,919 elderly participants (65 years and older) with Hcy levels between 12 and 50 µmol/L. Participants received daily either a tablet with 400 µg folic acid and 500 µg vitamin B12 (B-vitamin group) or a placebo tablet. Both tablets contained 15 µg vitamin D3. Data were available for global cognitive functioning assessed by Mini-Mental State Examination (n = 2,556), episodic memory (n = 2,467), attention and working memory (n = 759), information processing speed (n = 731), and executive function (n = 721). Results: Mean age was 74.1 (SD 6.5) years. Hcy concentrations decreased 5.0 (95% confidence interval −5.3 to −4.7) µmol/L in the B-vitamin group and 1.3 (−1.6 to −0.9) µmol/L in the placebo group. Cognitive domain scores did not differ over time between the 2 groups, as determined by analysis of covariance. Mini-Mental State Examination score decreased with 0.1 (−0.2 to 0.0) in the B-vitamin group and 0.3 (−0.4 to −0.2) in the placebo group (p = 0.05), as determined by an independent t test. Conclusions: Two-year folic acid and vitamin B12 supplementation did not beneficially affect performance on 4 cognitive domains in elderly people with elevated Hcy levels. It may slightly slow the rate of decline of global cognition, but the reported small difference may be attributable to chance. Classification of evidence: This study provides Class I evidence that 2-year supplementation with folic acid and vitamin B12 in hyperhomocysteinemic elderly people does not affect cognitive performance.

1,25-Dihydroxyvitamin D3 Influences Cellular Homocysteine Levels in Murine Preosteoblastic MC3T3-E1 Cells by Direct Regulation of Cystathionine β-Synthase

High homocysteine (HCY) levels are a risk factor for osteoporotic fracture. Furthermore, bone quality and strength are compromised by elevated HCY owing to its negative impact on collagen maturation. HCY is cleared by cystathionine β‐synthase (CBS), the first enzyme in the transsulfuration pathway. CBS converts HCY to cystathionine, thereby committing it to cysteine synthesis. A microarray experiment on MC3T3‐E1 murine preosteoblasts treated with 1,25‐dihydroxyvitamin D3 [1,25(OH)2D3] revealed a cluster of genes including the cbs gene, of which the transcription was rapidly and strongly induced by 1,25(OH)2D3. Quantitative real‐time PCR and Western blot analysis confirmed higher levels of cbs mRNA and protein after 1,25(OH)2D3 treatment in murine and human cells. Moreover, measurement of CBS enzyme activity and quantitative measurements of HCY, cystathionine, and cysteine concentrations were consistent with elevated transsulfuration activity in 1,25(OH)2D3‐treated cells. The importance of a functional vitamin D receptor (VDR) for transcriptional regulation of cbs was shown in primary murine VDR knockout osteoblasts, in which upregulation of cbs in response to 1,25(OH)2D3 was abolished. Chromatin immunoprecipitation on chip and transfection studies revealed a functional vitamin D response element in the second intron of cbs. To further explore the potential clinical relevance of our ex vivo findings, human data from the Longitudinal Aging Study Amsterdam suggested a correlation between vitamin D status [25(OH)D3 levels] and HCY levels. In conclusion, this study showed that cbs is a primary 1,25(OH)2D3 target gene which renders HCY metabolism responsive to 1,25(OH)2D3.

Physical capacity after 7 weeks of low-intensity wheelchair training

Purpose. To simulate the effect of low-intensity exercise in early rehabilitation, we investigated the effect of a 7-week low-intensity norm duration hand rim wheelchair training on the physical capacity in untrained able-bodied individuals. Method. Twenty-five able-bodied participants were randomly assigned to an experimental and control group: 10 participants exercised 7 weeks, three times a week at 30% heart rate reserve (HRR) for 30 min (experimental group). The control group consisted of 15 participants who did not receive training. Physical capacity (maximal isometric strength, sprint power, peak power output and peak oxygen uptake) and submaximal performance [heart rate (HR), oxygen uptake (VO2), mechanical efficiency (ME)] were assessed pre- and post-training. The levels of upper-body discomfort were determined with the use of a Local Perceived Discomfort scale. Results. Compared to the control group the experimental group significantly improved on sprint power (+31.2%), peak aerobic power output (+34%), submaximal HR, VO2 and ME (+16.9%). The participants did not experience high levels of local discomfort in the upper body during the training. Conclusions. Low-intensity norm duration hand rim wheelchair training which significantly improved peak aerobic and sprint power output, efficiency and physical strain in able-bodied untrained individuals. Training at 30% HRR (3 × /week, 30 min/session) may be appropriate in untrained individuals, such as novice wheelchair users at the start of their rehabilitation, to prevent early fatigue and overuse and enhance motivation. Please note that this article was published in error in a previous issue of the Journal. This paper was submitted and accepted as part of the Special Issue entitled 4th International State-of-the-art-Congress ‘Rehabilitation: Mobility, Exercise & Sports’ and has therefore been republished in this issue. The publisher apologises for this error.

Cross-sectional and longitudinal association between homocysteine, vitamin B12 and physical performance in older persons.

Background/Objectives:Decreases in physical performance are associated with multiple negative health outcomes. The objective of this study was to examine whether high plasma homocysteine and low serum vitamin B12 are independent risk factors for lower physical performance, both cross-sectionally and longitudinally.Subjects/Methods:This study was performed in persons aged ⩾65 years of the LASA (Longitudinal Aging Study Amsterdam), an ongoing cohort study. Blood was collected in 1995/1996 (n=1352). Physical performance was assessed in 1995/1996 and in 1998/1999 using three tests: the walking test, the chair stands test and the tandem stand (n=901–1155).Results:After adjustment for confounding, women in the highest quartile of homocysteine had a significantly lower physical performance than did those in the lowest quartile in the cross-sectional analyses (β=−0.93, s.e.=0.34, P<0.01). This association was borderline statistically significant in the longitudinal analyses (β=−0.69, s.e.=0.35, P=0.05). After additional adjustment for serum vitamin B12, both associations were statistically significant (P<0.05). For vitamin B12 in women, and for homocysteine and vitamin B12 in men, the observed associations were less consistent.Conclusions:High plasma homocysteine is an independent risk factor for lower physical performance in older women. The association between vitamin B12 and physical performance is less clear.

Non-linear associations between serum 25-OH vitamin D and indices of arterial stiffness and arteriosclerosis in an older population

BACKGROUND several studies have been pointing towards a non-linear relationship between serum 25(OH)D and cardiovascular disease. Next to vitamin D deficiency, also higher levels of 25(OH)D have been reported to be associated with increased cardiovascular risk. We aimed to investigate the nature of the relationship between serum 25(OH)D and measures of arterial stiffness and arteriosclerosis in an elderly population. DESIGN cross-sectional. SETTING/SUBJECTS a subgroup of the B-PROOF study was included to determine associations between serum 25(OH)D and arterial stiffness and atherosclerosis (n = 567, 57% male, age 72.6 ± 5.6 years, mean serum 25(OH)D 54.6 ± 24.1 nmol/l). METHODS carotid intima media thickness (IMT) was assessed using ultrasonography and pulse wave velocity (PWV) was determined with applanation tonometry. Associations were tested using multivariable restricted cubic spline functions and stratified linear regression analysis. RESULTS the associations between serum 25(OH)D and carotid IMT or PWV were non-linear. Spline functions demonstrated a difference between 25(OH)D deficient and sufficient individuals. In serum 25(OH)D sufficient participants (≥50 nmol/l; n = 287), a positive association with IMT and serum 25(OH)D was present (β 1.24; 95%CI [0.002; 2.473]). PWV levels were slightly lower in vitamin D deficient individuals, but the association with 25(OH)D was not significant. CONCLUSION our study demonstrates that associations of serum 25(OH)D and PWV and IMT in an elderly population are not linear. In particular from serum 25(OH)D levels of 50 nmol/l and up, there is a slight increase of IMT with increasing 25(OH)D levels.

The association between plasma homocysteine levels and bone quality and bone mineral density parameters in older persons

INTRODUCTION High plasma homocysteine levels have been associated with incident osteoporotic fractures, but the mechanisms underlying this association are still unknown. It has been hypothesized that homocysteine might interfere with collagen cross-linking in bone, thereby weakening bone structure. Therefore, we wanted to investigate whether plasma homocysteine levels are associated with bone quality parameters, rather than with bone mineral density. METHODS Cross-sectional data of the B-PROOF study (n=1227) and of two cohorts of the Rotterdam Study (RS-I (n=2850) and RS-II (n=2023)) were used. Data on bone mineral density of the femoral neck and lumbar spine were obtained in these participants using dual-energy X-ray assessment (DXA). In addition, participants of B-PROOF and RS-I underwent quantitative ultrasound measurement of the calcaneus, as a marker for bone quality. Multiple linear regression analysis was used to investigate the associations between natural-log transformed plasma levels of homocysteine and bone mineral density or ultrasound parameters. RESULTS Natural-log transformed homocysteine levels were inversely associated with femoral neck bone mineral density in the two cohorts of the Rotterdam Study (B=-0.025, p=0.004 and B=-0.024, p=0.024). In B-PROOF, no association was found. Pooled data analysis showed significant associations between homocysteine and bone mineral density at both femoral neck (B=-0.032, p=0.010) and lumbar spine (B=-0.098, p=0.021). Higher natural-log transformed homocysteine levels associated significantly with lower bone ultrasound attenuation in B-PROOF (B=-3.7, p=0.009) and speed of sound in both B-PROOF (B=-8.9, p=0.001) and RS-I (B=-14.5, p=0.003), indicating lower bone quality. Pooled analysis confirmed the association between homocysteine and SOS (B=-13.1, p=0.016). Results from ANCOVA-analysis indicate that differences in SOS and BUA between participants having a plasma homocysteine level above or below median correspond to 0.14 and 0.09 SD, respectively. DISCUSSION In this study, plasma levels of homocysteine were significantly inversely associated with both bone ultrasound parameters and with bone mineral density. However, the size of the associations seems to be of limited clinical relevance and may therefore not explain the previously observed association between plasma homocysteine and osteoporotic fracture incidence.