Recruitment and results of a pilot trial of vitamin D supplementation in the general population of Australia

Vitamin D Supplementation and the Incidence of Cataract Surgery in Older Australian Adults

PURPOSE

Observational studies suggest that higher serum 25-hydroxy vitamin D (25(OH)D) concentration may be associated with lower risk of cataract. However, no randomized controlled trials have assessed the effect of vitamin D supplementation on the incidence of cataract. We aimed to assess whether vitamin D supplementation reduces the incidence of cataract surgery.

DESIGN

We conducted an ancillary study of the D-Health Trial, a randomized, double-masked, placebo-controlled trial of monthly vitamin D conducted from 2014 through 2020 within the Australian general population.

PARTICIPANTS

We invited 421 207 men and women 60 to 84 years of age to participate; including an additional 1896 volunteers, 40 824 expressed interest. Those with hypercalcemia, hyperparathyroidism, kidney stones, osteomalacia, or sarcoidosis or those who were taking more than 500 international units (IU) supplemental vitamin D per day were excluded. A total of 21 315 were randomized, and 1390 participants did not fulfil the eligibility criteria for this analysis (linked data available, no cataract within first 6 months), leaving 19 925 included. The median follow-up was 5 years.

METHODS

Participants took 60 000 IU of vitamin D₃ (n = 10 662) or placebo (n = 10 653) orally once per month for a maximum of 5 years.

MAIN OUTCOME MEASURES

The primary outcome for this analysis was the first surgical treatment for cataract, ascertained through linkage to universal health insurance records and hospital data.

RESULTS

Among 19 925 participants eligible for this analysis (mean age, 69.3 years; 46% women) 3668 participants (18.4%) underwent cataract surgery during follow-up (vitamin D: n = 1841 [18.5%]; placebo: n = 1827 [18.3%] ). The incidence of cataract surgery was similar between the two groups (incidence rate, 41.6 and 41.1 per 1000 person-years in the vitamin D and placebo groups, respectively; hazard ratio, 1.02; 95% confidence interval, 0.95-1.09). In prespecified subgroup analyses, the effect of vitamin D supplementation on the incidence of cataract surgery was not modified by age, sex, body mass index, predicted serum 25(OH)D concentration, or ambient ultraviolet radiation.

CONCLUSIONS

Routinely supplementing older adults who live in an area with a low prevalence of vitamin D deficiency with high-dose vitamin D is unlikely to reduce the need for cataract surgery.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

Effects of Vitamin D Supplementation on Telomere Length: An Analysis of Data from the Randomised Controlled D-Health Trial

OBJECTIVES

Observational studies have suggested that a higher 25-hydroxyvitamin D concentration may be associated with longer telomere length; however, this has not been investigated in randomised controlled trials. We conducted an ancillary study within a randomised, double-blind, placebo-controlled trial of monthly vitamin D (the D-Health Trial) for the prevention of all-cause mortality, conducted from 2014 to 2020, to assess the effect of vitamin D supplementation on telomere length (measured as the telomere to single copy gene (T/S) ratio).

DESIGN, SETTING, PARTICIPANTS, AND INTERVENTION

Participants were Australians aged 60-84 years and we randomly selected 1,519 D-Health participants (vitamin D: n=744; placebo: n=775) for this analysis. We used quantitative polymerase chain reaction to measure the relative telomere length (T/S ratio) at 4 or 5 years after randomisation. We compared the mean T/S ratio between the vitamin D and placebo groups to assess the effect of vitamin D supplementation on relative telomere length, using a linear regression model with adjustment for age, sex, and state which were used to stratify the randomisation.

RESULTS

The mean T/S ratio was 0.70 for both groups (standard deviation 0.18 and 0.16 for the vitamin D and placebo groups respectively). The adjusted mean difference (vitamin D minus placebo) was -0.001 (95% CI -0.02 to 0.02). There was no effect modification by age, sex, body mass index, or predicted baseline 25-hydroxyvitamin D concentration.

CONCLUSION

In conclusion, routinely supplementing older adults, who are largely vitamin D replete, with monthly doses of vitamin D is unlikely to influence telomere length.

Screening for Vitamin D Deficiency in Adults: Updated Evidence Report and Systematic Review for the US Preventive Services Task Force

IMPORTANCE

Low serum vitamin D levels have been associated with adverse clinical outcomes; identifying and treating deficiency may improve outcomes.

OBJECTIVE

To review the evidence about screening for vitamin D deficiency in adults.

DATA SOURCES

PubMed, EMBASE, the Cochrane Library, and trial registries through March 12, 2020; bibliographies from retrieved articles, outside experts, and surveillance of the literature through November 30, 2020.

STUDY SELECTION

Fair- or good-quality, English-language randomized clinical trials (RCTs) of screening with serum 25-hydroxyvitamin D (25[OH]D) compared with no screening, or treatment with vitamin D (with or without calcium) compared with placebo or no treatment conducted in nonpregnant adults; nonrandomized controlled intervention studies for harms only. Treatment was limited to studies enrolling or analyzing participants with low serum vitamin D levels.

DATA EXTRACTION AND SYNTHESIS

Two reviewers assessed titles/abstracts and full-text articles, extracted data, and assessed study quality; when at least 3 similar studies were available, meta-analyses were conducted.

MAIN OUTCOMES AND MEASURES

Mortality, incident fractures, falls, diabetes, cardiovascular events, cancer, depression, physical functioning, and infection.

RESULTS

Forty-six studies (N = 16 205) (77 publications) were included. No studies directly evaluated the health benefits or harms of screening. Among community-dwelling populations, treatment was not significantly associated with mortality (pooled absolute risk difference [ARD], 0.3% [95% CI, -0.6% to 1.1%]; 8 RCTs, n = 2006), any fractures (pooled ARD, -0.3% [95% CI, -2.1% to 1.6%]; 6 RCTs, n = 2186), incidence of diabetes (pooled ARD, 0.1% [95% CI, -1.3% to 1.6%]; 5 RCTs, n = 3356), incidence of cardiovascular disease (2 RCTs; hazard ratio, 1.00 [95% CI, 0.74 to 1.35] and 1.09 [95% CI, 0.68 to 1.76]), incidence of cancer (2 RCTs; hazard ratio, 0.97 [95% CI, 0.68 to 1.39] and 1.01 [95% CI, 0.65 to 1.58], or depression (3 RCTs, various measures reported). The pooled ARD for incidence of participants with 1 or more falls was -4.3% (95% CI, -11.6% to 2.9%; 6 RCTs). The evidence was mixed for the effect of treatment on physical functioning (2 RCTs) and limited for the effect on infection (1 RCT). The incidence of adverse events and kidney stones was similar between treatment and control groups.

CONCLUSIONS AND RELEVANCE

No studies evaluated the direct benefits or harms of screening for vitamin D deficiency. Among asymptomatic, community-dwelling populations with low vitamin D levels, the evidence suggests that treatment with vitamin D has no effect on mortality or the incidence of fractures, falls, depression, diabetes, cardiovascular disease, cancer, or adverse events. The evidence is inconclusive about the effect of treatment on physical functioning and infection.

High-dose vitamin D supplementation to prevent prostate cancer progression in localised cases with low-to-intermediate risk of progression on active surveillance (ProsD): protocol of a phase II randomised controlled trial

INTRODUCTION

Active surveillance (AS) for patients with prostate cancer (PC) with low risk of PC death is an alternative to radical treatment. A major drawback of AS is the uncertainty whether a patient truly has low risk PC based on biopsy alone. Multiparametric MRI scan together with biopsy, appears useful in separating patients who need curative therapy from those for whom AS may be safe. Two small clinical trials have shown short-term high-dose vitamin D supplementation may prevent PC progression. There is no substantial evidence for its long-term safety and efficacy, hence its use in the care of men with PC on AS needs assessment. This protocol describes the ProsD clinical trial which aims to determine if oral high-dose vitamin D supplementation taken monthly for 2 years can prevent PC progression in cases with low-to-intermediate risk of progression.

METHOD AND ANALYSIS

This is an Australian national multicentre, 2:1 double-blinded placebo-controlled phase II randomised controlled trial of monthly oral high-dose vitamin D supplementation (50 000 IU cholecalciferol), in men diagnosed with localised PC who have low-to-intermediate risk of disease progression and are being managed by AS. This trial will assess the feasibility, efficacy and safety of supplementing men with an initial oral loading dose of 500 000 IU cholecalciferol, followed by a monthly oral dose of 50 000 IU during the 24 months of AS. The primary trial outcome is the commencement of active therapy for clinical or non-clinical reason, within 2 years of AS.

ETHICS AND DISSEMINATION

This trial is approved by Bellberry Ethics Committee (2016-06-459). All results will be reported in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

ACTRN12616001707459.

The effect of vitamin D supplementation on the risk of breast cancer: a trial sequential meta-analysis

BACKGROUND AND OBJECTIVE

Observational studies suggest an inverse association between circulating vitamin D levels and risk of breast cancer. However, the potential benefits of vitamin D supplementation to reduce the risk of breast cancer remain controversial, based on the results of current randomized controlled trials (RCTs). The aim of this study was to evaluate the value of vitamin D supplementation on breast cancer prevention.

METHODS

PubMed, Embase, and Cochrane library were searched from inception to February 2020. We performed a trial sequential meta-analysis of RCTs reporting the effect of vitamin D supplementation, with or without calcium, on the risk of breast cancer. The effect was estimated using a relative risk reduction threshold of 30%.

RESULTS

Eight trials comprising 72,275 participants were included in this study, with a median follow-up period ranging from 1 to 11.9 years. The median dosage of vitamin D supplementation was 967 IU per day (range 400-3704 IU per day) across the trials. This study yielded a relative risk of 1.04 (95% CI 0.85-1.29, P = 0.68) for the effect of vitamin D supplementation (6 trials, 33,472 participants), and 0.99 (95% CI 0.91-1.07, P = 0.73) for co-administration of vitamin D and calcium (4 trials, 41,957 participants). The effect estimate for vitamin D with or without calcium on breast cancer risk lay within the futility boundary, indicating that vitamin D supplementation does not alter the relative risk by 30% or more.

CONCLUSION

Our analyses suggest that vitamin D supplementation, with or without calcium, does not reduce breast cancer risk by 30% or more. Future trials with similar designs are unlikely to alter this finding.

Vitamin D C3-epimer levels are proportionally higher with oral vitamin D supplementation compared to ultraviolet irradiation of skin in mice but not humans

A proportion of circulating 25-hydroxy vitamin D₃ (25(OH)D₃₎) undergoes epimerization to form C3-epi 25(OH)D₃ and C3-epi 1,25(OH)₂D₃. These epimers have less calcaemic activity than non-epimerized metabolites and are not differentiated by many immunoassays when reporting total 25(OH)D₃ levels. This study aimed to compare the effect of exposure to ultraviolet radiation (UVR) and oral vitamin D₃ supplementation on vitamin D C3-epimer levels. C57Bl/6 female mice were fed either vitamin D-sufficient (vitamin D₃ 2000 IU/kg) or -deficient diets (no vitamin D₃) for 4 weeks. Among the vitamin D-deficient group, the shaved backs of half were irradiated daily for 4 days with 1 kJ/m² UVR, followed by twice weekly irradiation for 4 weeks. Despite similar 25(OH)D₃ levels, the UV-irradiated group had a lower proportion of C3-epi 25(OH)D₃ at week 7 (p < 0.05) and week 9 (p < 0.01). C3-epimer concentrations and %C3-epi 25(OH)D₃ were also analysed in serum samples from two human clinical trials. These trials investigated the effect of high dose oral vitamin D₃ supplementation and narrowband UVB phototherapy, respectively. Serum 25(OH)D₃ and the %C3-epi 25(OH)D₃ levels measured at 12 months after oral vitamin D₃ supplementation were not significantly different to those measured at the time of maximal effect of phototherapy (2 months). Thus, the proportion of 25(OH)D₃ that undergoes epimerization is greater with oral vitamin D₃ supplementation than exposure to UVR in mice, but not in humans. This important difference between human and murine vitamin D metabolism warrants consideration when interpreting animal studies.

Assessment of research waste part 2: wrong study populations- an exemplar of baseline vitamin D status of participants in trials of vitamin D supplementation

BACKGROUND

Research waste can occur when trials are conducted in the wrong populations. Vitamin D deficient populations are most likely to benefit from vitamin D supplementation. We investigated waste attributable to randomised controlled trials (RCTs) of supplementation in populations that were not vitamin D deficient.

METHODS

In December 2015, we searched Pubmed, recent systematic reviews, and three trial registries for RCTs of vitamin D with clinical endpoints in adults, and 25-hydroxvitamin D (25OHD) survey data relevant to large (N ≥ 1000) RCTs. We investigated the proportion of RCTs that studied vitamin D deficient populations, temporal trends in baseline 25OHD, and whether investigators in large RCTs considered relevant 25OHD survey data or systematic reviews in their trial justifications.

RESULTS

Of 137 RCTs of vitamin D with clinical endpoints, 118 (86%) reported baseline mean/median 25OHD, which was < 25, 25-49, 50-74, and ≥ 75 nmol/L in 12 (10%), 62 (53%), 36 (31%), and 8 (7%) RCTs, respectively. In 70% of RCTs, baseline 25OHD was > 40 nmol/L. Baseline 25OHD increased over time. Before 2006, 38%, 62%, 0% and 0% of RCTs had baseline 25OHD < 25, 25-49, 50-74, and ≥ 75 nmol/L respectively; in 2011-15, the respective proportions were 9%, 49%, 37%, and 6%. Of 12 RCTs with baseline 25OHD < 25 nmol/L, 8 had neutral findings. Of 25 large RCTs (18 completed, 7 ongoing), 1 was undertaken in a vitamin D deficient population, 3 in vitamin D insufficient populations, and 17 had, or probably will have, baseline 25OHD > 40 nmol/L. 44% (8/18) of large completed RCTs cited relevant prior population 25OHD data, and only 3/10 (30%) relevant prior systematic reviews.

CONCLUSIONS

Up to 70% of RCTs of vitamin D with clinical endpoints, 71% of large completed RCTs, and 100% of ongoing large RCTs could be considered research waste because they studied cohorts that were not vitamin D deficient.

Effects of vitamin D supplementation on markers for cardiovascular disease and type 2 diabetes: an individual participant data meta-analysis of randomized controlled trials

Background

Evidence from randomized controlled trials (RCTs) for the causal role of vitamin D on noncommunicable disease outcomes is inconclusive.

Objective

The aim of this study was to investigate whether there are beneficial or harmful effects of cholecalciferol (vitamin D3) supplementation according to subgroups of remeasured serum 25-hydroxyvitamin D [25(OH)D] on cardiovascular and glucometabolic surrogate markers with the use of individual participant data (IPD) meta-analysis of RCTs.

Design

Twelve RCTs (16 wk to 1 y of follow-up) were included. For standardization, 25(OH)D concentrations for all participants (n = 2994) at baseline and postintervention were re-measured in bio-banked serum samples with the use of a certified liquid chromatography-tandem mass spectrometry method traceable to a reference measurement procedure. IPD meta-analyses were performed according to subgroups of remeasured 25(OH)D. Main outcomes were blood pressure and glycated hemoglobin (HbA1c). Secondary outcomes were LDL, HDL, and total cholesterol and triglycerides; parathyroid hormone (PTH); fasting glucose, insulin, and C-peptide; and 2-h glucose. In secondary analyses, other potential effect modifiers were studied.

Results

Remeasurement of 25(OH)D resulted in a lower mean 25(OH)D concentration in 10 of 12 RCTs. Vitamin D supplementation had no effect on the main outcomes of blood pressure and HbA1c. Supplementation resulted in 10-20% lower PTH concentrations, irrespective of the 25(OH)D subgroups. The subgroup analyses according to achieved 25(OH)D concentrations showed a significant decrease in LDL-cholesterol concentrations after vitamin D supplementation in 25(OH)D subgroups with <75, <100, and <125 nmol of -0.10 mmol/L (95% CI: -0.20, -0.00 mmol/L), -0.10 mmol/L (95% CI: -0.18, -0.02 mmol/L), and -0.07 mmol/L (95% CI: -0.14, -0.00 mmol/L), respectively. Patient features that modified the treatment effect could not be identified.

Conclusions

For the main outcomes of blood pressure and HbA1c, the data support no benefit for vitamin D supplementation. For the secondary outcomes, in addition to its effect on PTH, we observed indications for a beneficial effect of vitamin D supplementation only on LDL cholesterol, which warrants further investigation. This trial was registered at www.clinicaltrials.gov as NCT02551835.

Cancer and vitamin D supplementation: a systematic review and meta-analysis

Background

Low 25-hydroxyvitamin D status has been associated with a higher risk of cancer in epidemiologic studies.

Objective

The aim of this study was to undertake a systematic review and meta-analysis of randomized clinical trials (RCTs) investigating the effect of vitamin D supplementation alone on cancer incidence and mortality.

Design

A systematic review was undertaken. MEDLINE, Embase, CENTRAL, conference abstracts, and clinical trial registries were searched (last search March 2017) for RCTs investigating vitamin D supplementation alone. RCTs with ≥12 mo of follow-up and in participants with a mean or median age ≥60 y were eligible. During-study events were used as the main analysis, but after-study events were included in a secondary analysis. Subgroup analyses concerning different forms of vitamin D supplementation, 25-hydroxyvitamin D status at baseline, vitamin D dose, and exclusion of open-label trials were undertaken.

Results

Thirty studies in 18,808 participants were included in the systematic review, with a median follow-up ranging from 1 to 6.2 y. The results of the meta-analysis for during-study events showed no evidence of an effect of vitamin D supplementation for cancer incidence (RR: 1.03; 95% CI: 0.91, 1.15) and cancer-related deaths (RR: 0.88; 95% CI: 0.70, 1.09). Including after-study events, the RRs were 1.02 (95% CI: 0.92, 1.13) and 0.86 (95% CI: 0.72, 1.03), respectively. These results did not appear to be affected by baseline 25-hydroxyvitamin D status, vitamin D dose, or the exclusion of open-label trials.

Conclusion

We did not find evidence to suggest that vitamin D supplementation alone reduces the incidence of cancer or cancer mortality, even after including long-term follow-up results.

Hypercalcemia, hypercalciuria, and kidney stones in long-term studies of vitamin D supplementation: a systematic review and meta-analysis

BACKGROUND

Vitamin D supplementation is increasingly being used in higher doses in randomized controlled trials (RCTs). However, adverse events from very large annual doses of vitamin D have been shown in 2 RCTs, whereas in a third RCT, low-dose vitamin D, with calcium supplements, was shown to increase kidney stone risk.

OBJECTIVE

We analyzed the side effects related to calcium metabolism in RCTs, specifically hypercalcemia, hypercalciuria, and kidney stones, in participants who were given vitamin D supplements for ≥24 wk compared with in subjects in the placebo arm.

DESIGN

The following 3 main online databases were searched: Ovid Medline (PubMed), EMBASE, and the Cochrane Library. Software was used for the meta-analysis.

RESULTS

A total of 48 studies with 19,833 participants were identified, which reported ≥1 of the following side effects: hypercalcemia, hypercalciuria, or kidney stones. Of these studies, kidney stones were reported in only 9 trials with a tendency for fewer subjects reporting stones in the vitamin D arm than in the placebo arm (RR: 0.66, 95% CI: 0.41, 1.09; P = 0.10). In 37 studies, hypercalcemia was shown with increased risk shown for the vitamin D group (RR: 1.54; 95% CI: 1.09, 2.18; P = 0.01). Similar increased risk of hypercalciuria was shown in 14 studies for the vitamin D group (RR: 1.64; 95% CI: 1.06, 2.53; P = 0.03). In subgroup analyses, it was shown that the effect of vitamin D supplementation on risk of hypercalcemia, hypercalciuria, or kidney stones was not modified by baseline 25-hydroxyvitamin D, vitamin D dose and duration, or calcium co-supplementation.

CONCLUSIONS

Long-term vitamin D supplementation resulted in increased risks of hypercalcemia and hypercalciuria, which were not dose related. However, vitamin D supplementation did not increase risk of kidney stones. Additional large RCTs of long-term vitamin D supplementation are required to confirm these findings.

Effect of vitamin D supplementation on selected inflammatory biomarkers in older adults: a secondary analysis of data from a randomised, placebo-controlled trial

Observational studies have suggested that 25-hydroxyvitamin D (25(OH)D) levels are associated with inflammatory markers. Most trials reporting significant associations between vitamin D intake and inflammatory markers used specific patient groups. Thus, we aimed to determine the effect of supplementary vitamin D using secondary data from a population-based, randomised, placebo-controlled, double-blind trial (Pilot D-Health trial 2010/0423). Participants were 60- to 84-year-old residents of one of the four eastern states of Australia. They were randomly selected from the electoral roll and were randomised to one of three trial arms: placebo (n 214), 750 μg (n 215) or 1500 μg (n 215) vitamin D3, each taken once per month for 12 months. Post-intervention blood samples for the analysis of C-reactive protein (CRP), IL-6, IL-10, leptin and adiponectin levels were available for 613 participants. Associations between intervention group and biomarker levels were evaluated using quantile regression. There were no statistically significant differences in distributions of CRP, leptin, adiponectin, leptin:adiponectin ratio or IL-10 levels between the placebo group and either supplemented group. The 75th percentile IL-6 level was 2·8 pg/ml higher (95 % CI 0·4, 5·8 pg/ml) in the 1500 μg group than in the placebo group (75th percentiles:11·0 v. 8·2 pg/ml), with a somewhat smaller, non-significant difference in 75th percentiles between the 750 μg and placebo groups. Despite large differences in serum 25(OH)D levels between the three groups after 12 months of supplementation, we found little evidence of an effect of vitamin D supplementation on cytokine or adipokine levels, with the possible exception of IL-6.

Comparing the effects of sun exposure and vitamin D supplementation on vitamin D insufficiency, and immune and cardio-metabolic function: the Sun Exposure and Vitamin D Supplementation (SEDS) Study

Background

Adults living in the sunny Australian climate are at high risk of skin cancer, but vitamin D deficiency (defined here as a serum 25-hydroxyvitamin D (25(OH)D) concentration of less than 50 nmol/L) is also common. Vitamin D deficiency may be a risk factor for a range of diseases. However, the optimal strategies to achieve and maintain vitamin D adequacy (sun exposure, vitamin D supplementation or both), and whether sun exposure itself has benefits over and above initiating synthesis of vitamin D, remain unclear.

The Sun Exposure and Vitamin D Supplementation (SEDS) Study aims to compare the effectiveness of sun exposure and vitamin D supplementation for the management of vitamin D insufficiency, and to test whether these management strategies differentially affect markers of immune and cardio-metabolic function.

Methods/Design

The SEDS Study is a multi-centre, randomised controlled trial of two different daily doses of vitamin D supplementation, and placebo, in conjunction with guidance on two different patterns of sun exposure. Participants recruited from across Australia are aged 18–64 years and have a recent vitamin D test result showing a serum 25(OH)D level of 40–60 nmol/L.

Discussion

This paper discusses the rationale behind the study design, and considers the challenges but necessity of data collection within a non-institutionalised adult population, in order to address the study aims. We also discuss the challenges of participant recruitment and retention, ongoing engagement of referring medical practitioners and address issues of compliance and participant retention.

Trial registration

Australia New Zealand Clinical Trials Registry: ACTRN12613000290796 Registered 14 March 2013.

Environmental, personal, and genetic determinants of response to vitamin D supplementation in older adults

CONTEXT AND OBJECTIVE

Suboptimal vitamin D status can be corrected by vitamin D supplementation, but individual responses to supplementation vary. We aimed to examine genetic and nongenetic determinants of change in serum 25-hydroxyvitamin D (25(OH)D) after supplementation.

DESIGN AND PARTICIPANTS

We used data from a pilot randomized controlled trial in which 644 adults aged 60 to 84 years were randomly assigned to monthly doses of placebo, 30 000 IU, or 60 000 IU vitamin D3 for 12 months. Baseline characteristics were obtained from a self-administered questionnaire. Eighty-eight single-nucleotide polymorphisms (SNPs) in 41 candidate genes were genotyped using Sequenom MassArray technology. Serum 25(OH)D levels before and after the intervention were measured using the Diasorin Liaison platform immunoassay. We used linear regression models to examine associations between genetic and nongenetic factors and change in serum 25(OH)D levels.

RESULTS

Supplement dose and baseline 25(OH)D level explained 24% of the variability in response to supplementation. Body mass index, self-reported health status, and ambient UV radiation made a small additional contribution. SNPs in CYP2R1, IRF4, MC1R, CYP27B1, VDR, TYRP1, MCM6, and HERC2 were associated with change in 25(OH)D level, although only CYP2R1 was significant after adjustment for multiple testing. Models including SNPs explained a similar proportion of variability in response to supplementation as models that included personal and environmental factors.

CONCLUSION

Stepwise regression analyses suggest that genetic variability may be associated with response to supplementation, perhaps suggesting that some people might need higher doses to reach optimal 25(OH)D levels or that there is variability in the physiologically normal level of 25(OH)D.

Effect of vitamin D supplementation on antibiotic use: a randomized controlled trial

BACKGROUND

Observational data suggested that supplementation with vitamin D could reduce risk of infection, but trial data are inconsistent.

OBJECTIVE

We aimed to examine the effect of oral vitamin D supplementation on antibiotic use.

DESIGN

We conducted a post hoc analysis of data from pilot D-Health, which is a randomized trial carried out in a general community setting between October 2010 and February 2012. A total of 644 Australian residents aged 60-84 y were randomly assigned to receive monthly doses of a placebo (n = 214) or 30,000 (n = 215) or 60,000 (n = 215) IU oral cholecalciferol for ≤12 mo. Antibiotics prescribed during the intervention period were ascertained by linkage with pharmacy records through the national health insurance scheme (Medicare Australia).

RESULTS

People who were randomly assigned 60,000 IU cholecalciferol had nonsignificant 28% lower risk of having antibiotics prescribed at least once than did people in the placebo group (RR: 0.72; 95% CI: 0.48, 1.07). In analyses stratified by age, in subjects aged ≥70 y, there was a significant reduction in antibiotic use in the high-dose vitamin D compared with placebo groups (RR: 0.53; 95% CI: 0.32, 0.90), whereas there was no effect in participants aged <70 y (RR: 1.07; 95% CI: 0.58, 1.97) (P-interaction = 0.1).

CONCLUSION

Although this study was a post hoc analysis and statistically nonsignificant, this trial lends some support to the hypothesis that supplementation with 60,000 IU vitamin D/mo is associated with lower risk of infection, particularly in older adults. The trial was registered at the Australian New Zealand Clinical Trials Registry (anzctr.org.au) as ACTRN12609001063202.

Predicting vitamin D deficiency in older Australian adults

OBJECTIVE

There has been a dramatic increase in vitamin D testing in Australia in recent years, prompting calls for targeted testing. We sought to develop a model to identify people most at risk of vitamin D deficiency.

DESIGN AND PARTICIPANTS

This is a cross-sectional study of 644 60- to 84-year-old participants, 95% of whom were Caucasian, who took part in a pilot randomized controlled trial of vitamin D supplementation.

MEASUREMENTS

Baseline 25(OH)D was measured using the Diasorin Liaison platform. Vitamin D insufficiency and deficiency were defined using 50 and 25 nmol/l as cut-points, respectively. A questionnaire was used to obtain information on demographic characteristics and lifestyle factors. We used multivariate logistic regression to predict low vitamin D and calculated the net benefit of using the model compared with 'test-all' and 'test-none' strategies.

RESULTS

The mean serum 25(OH)D was 42 (SD 14) nmol/1. Seventy-five per cent of participants were vitamin D insufficient and 10% deficient. Serum 25(OH)D was positively correlated with time outdoors, physical activity, vitamin D intake and ambient UVR, and inversely correlated with age, BMI and poor self-reported health status. These predictors explained approximately 21% of the variance in serum 25(OH)D. The area under the ROC curve predicting vitamin D deficiency was 0·82. Net benefit for the prediction model was higher than that for the 'test-all' strategy at all probability thresholds and higher than the 'test-none' strategy for probabilities up to 60%.

CONCLUSION

Our model could predict vitamin D deficiency with reasonable accuracy, but it needs to be validated in other populations before being implemented.