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

Vitamin D-Do Diet Recommendations for Health Remain Strong?

How will the scientific community and authoritative bodies define future nutritional requirements for vitamin D? At the International Symposium on Nutritional Aspects of Musculoskeletal Health, the authors debated the strength of current evidence for setting vitamin D intake recommendations from diet: the positive side of the strength of the evidence (PRO) suggests there is a physiological requirement for vitamin D and the opposing view (CON) that in light of negative results from large, recent trials, particularly those with fractures and bone health outcomes, we are left rudderless. Should we provide recommendations based on empiric treatment of vitamin D for most groups and conditions? It is becoming increasingly evident that vitamin D plays a role in many physiological functions and processes associated with long-term human health; however, to what extent are these benefits apparent beyond what is needed for adequate nutritional status, measured as serum 25-hydroxyvitamin D levels, for active calcium absorption? The meeting attendees voted for the PRO vs. CON position at the end of the session.

Several methods for assessing research waste in reviews with a systematic search: a scoping review

Background

Research waste is present in all study designs and can have significant consequences for science, including reducing the reliability of research findings and contributing to the inefficient use of resources. Estimates suggest that as much as 85% of all biomedical research is wasted. However, it is uncertain how avoidable research waste is assessed in specific types of study designs and what methods could be used to examine different aspects of research waste. We aimed to investigate which methods, systematic reviews, scoping reviews, and overviews of reviews discussing research waste, have used to assess avoidable research waste.

Materials and Methods

We published a protocol in the Open Science Framework prospectively (https://osf.io/2fbp4). We searched PubMed and Embase with a 30-year limit (January 1993-August 2023). The concept examined was how research waste and related synonyms (e.g., unnecessary, redundant, duplicate, etc.) were assessed in reviews with a systematic search: systematic, scoping, or overviews of reviews. We extracted data on the method used in the review to examine for research waste and for which study design this method was applied.

Results

The search identified 4,285 records of which 93 reviews with systematic searches were included. The reviews examined a median of 90 (range 10-6,781) studies, where the study designs most commonly included were randomized controlled trials (48%) and systematic reviews (33%). In the last ten years, the number of reports assessing research waste has increased. More than 50% of examined reviews reported evaluating methodological research waste among included studies, typically using tools such as one of Cochrane Risk of Bias tools (n = 8) for randomized controlled trials or AMSTAR 1 or 2 (n = 12) for systematic reviews. One fourth of reviews assessed reporting guideline adherence to e.g., CONSORT (n = 4) for randomized controlled trials or PRISMA (n = 6) for systematic reviews.

Conclusion

Reviews with systematic searches focus on methodological quality and reporting guideline adherence when examining research waste. However, this scoping review revealed that a wide range of tools are used, which may pose difficulties in comparing examinations and performing meta-research. This review aids researchers in selecting methodologies and contributes to the ongoing discourse on optimizing research efficiency.

Vitamin D Supplementation: A Review of the Evidence Arguing for a Daily Dose of 2000 International Units (50 µg) of Vitamin D for Adults in the General Population

Vitamin D deficiency is considered a public health problem due to its worldwide high prevalence and adverse clinical consequences regarding musculoskeletal health. In addition, vitamin D may also be crucial for the prevention of certain extraskeletal diseases. Despite decades of intensive scientific research, several knowledge gaps remain regarding the precise definition of vitamin D deficiency and sufficiency, the health benefits of improving vitamin D status, and the required vitamin D intakes. Consequently, various societies and expert groups have released heterogeneous recommendations on the dosages for vitamin D supplementation. In this brief narrative review, we outline and discuss recent advances regarding the scientific evidence arguing for a daily vitamin D supplementation with 2000 international units (IU) (50 µg) of vitamin D3 to prevent and treat vitamin D deficiency. According to data from randomized controlled trials (RCTs), such a dose may improve some health outcomes and is sufficient to raise and maintain serum 25(OH)D concentrations above 50 nmol/L (20 ng/mL) and above 75 nmol/L (30 ng/mL) in >99% and >90% of the general adult population, respectively. According to large vitamin D RCTs, there are no significant safety concerns in supplementing such a dose for several years, even in individuals with an already sufficient vitamin D status at baseline. A daily vitamin D supplementation with 2000 IU (50 µg) may be considered a simple, effective, and safe dosage to prevent and treat vitamin D deficiency in the adult general population.

Associations of the serum vitamin D with mortality in postmenopausal women

PURPOSE

Current evidence on the association of serum vitamin D with mortality in postmenopausal women is limited and inconsistent. Therefore, the purpose of this study was to examine the relationship between serum vitamin D and mortality in postmenopausal women.

METHODS

In this study, we used data from the NHANES (2001-2018) and conducted a multivariate Cox regression model to examine associations between serum vitamin D and all-cause mortality, cardiovascular mortality (CVD), and cancer mortality.

RESULTS

In a median follow-up period of 8.3 years, 1905 deaths of all causes were reported, 601 were due to CVD, and 385 deaths were due to cancer. After multivariable adjustment, higher serum vitamin D levels were significantly associated with a reduced risk of death. Compared to participants with lower vitamin D levels (<25 nmol/L), those with higher vitamin D levels (≥75.0 nmol/L) had a lower risk of all-cause mortality (hazard ratio 0.60, 95 % confidence interval 0.49 to 0.74), a lower risk of cardiovascular mortality (0.51, 0.35 to 0.74), and a lower risk of cancer mortality (0.43, 0.28 to 0.67). Moreover, we observed an L-shaped dose-response relationship of serum vitamin D levels with all-cause mortality, and cancer mortality, with this inflexion point being 55.9 nmol/L, and 51.2 nmol/L, respectively.

CONCLUSIONS

Higher concentrations of serum vitamin D substantially correlated with a reduction in mortality risk from all-cause, CVD, and cancer in postmenopausal women. These results imply that upholding adequate vitamin D levels may help prevent premature death in postmenopausal women.

Muscle Traits, Sarcopenia, and Sarcopenic Obesity: A Vitamin D Mendelian Randomization Study

(1) Background: Observational studies associate vitamin D deficiency with muscle disorders, while some clinical trial data support a minor association between the vitamin and skeletal muscle performance in healthy subjects. Vitamin D receptor knockout mice studies confirm the relationship between vitamin D and skeletal muscle; however, causal inference in humans is challenging due to the ethical implications of including vitamin D-deficient participants in randomized trials. This study uses genetic methods to safely explore causal underpinnings for the relationship between 25(OH)D concentrations and skeletal muscle-related traits, including grip strength and combined arm skeletal muscle mass, and extends this analysis to suspected pathophysiology in the form of probable sarcopenia and sarcopenic obesity. (2) Methods: We conducted Mendelian randomization (MR) analyses in up to 307,281 participants from the UK Biobank of whom 25,414 had probable sarcopenia and 16,520 had sarcopenic obesity. In total, 35 variants were used to instrument 25(OH)D and MR analyses conducted using multiple approaches. (3) Results: Genetic analyses provided support for a relationship between genetically predicted higher 25(OH)D and skeletal muscle traits, with linear MR analyses for grip strength showing 0.11 kg (95% CI 0.04, 0.19) greater contractile force per 10 unit higher 25(OH)D, while there was a modest association with skeletal muscle mass (0.01 kg (95% CI 0.003, 0.02) greater muscle mass). For probable sarcopenia risk, there was suggestive evidence for lower odds by higher 25(OH)D (OR 0.96 (95% CI 0.92, 1.00)); however, this did not reflect an association with sarcopenic obesity (OR 0.97 (95% CI 0.93, 1.02)), but was seen in probable sarcopenia cases who were not obese (OR 0.92 (95% CI 0.86, 0.98)). Results were similar across multiple MR approaches. (4) Conclusions: Our study supports a causal relationship between 25(OH)D and skeletal muscle health. While evidence for benefit did not extend to lower risk of sarcopenic obesity, effective vitamin D-deficiency prevention strategies may help reduce age-related muscle weakness.

EMAS position statement: Vitamin D and menopausal health

INTRODUCTION

There is increasing evidence that vitamin D has widespread tissue effects. In addition to osteoporosis, vitamin D deficiency has been associated with cardiovascular disease, diabetes, cancer, infections and neurodegenerative disease. However, the effect of vitamin D supplementation on non-skeletal outcomes requires clarification, especially in postmenopausal women.

AIM

This position statement provides an evidence-based overview of the role of vitamin D in the health of postmenopausal women based on observational and interventional studies.

MATERIALS AND METHODS

Literature review and consensus of expert opinion.

RESULTS AND CONCLUSIONS

Vitamin D status is determined by measuring serum 25-hydroxyvitamin D levels. Concentrations <20 ng/ml (<50 nmol/l) and <10 ng/ml (<25 nmol/l) are considered to constitute vitamin D deficiency and severe deficiency, respectively. Observational data suggest an association between vitamin D deficiency and adverse health outcomes in postmenopausal women, although they cannot establish causality. The evidence from randomized controlled trials concerning vitamin D supplementation is not robust, since many studies did not consider whether people were deficient at baseline. Moreover, high heterogeneity exists in terms of the population studied, vitamin D dosage, calcium co-administration and duration of intervention. Concerning skeletal health, vitamin D deficiency is associated with low bone mass and an increased risk of fractures. Vitamin D supplementation at maintenance doses of 800-2000 IU/day (20-50 μg/day), after repletion of vitamin D status with higher weekly or daily doses, may be of benefit only when co-administered with calcium (1000-1200 mg/day), especially in the elderly populations and those with severe vitamin D deficiency. Concerning cardiovascular disease, vitamin D deficiency is associated with an increased prevalence of cardiovascular risk factors, mainly metabolic syndrome, type 2 diabetes mellitus and dyslipidemia. Vitamin D deficiency, especially its severe form, is associated with an increased risk of cardiovascular events (coronary heart disease, stroke, mortality), independently of traditional risk factors. Vitamin D supplementation may have a modestly beneficial effect on lipid profile and glucose homeostasis, especially in obese individuals or those ≥60 years old and at doses of ≥2000 IU/day (≥50 μg/day). However, it has no effect on the incidence of cardiovascular events. Concerning cancer, vitamin D deficiency is associated with increased incidence of and mortality from several types of cancer, such as colorectal, lung and breast cancer. However, the data on other types of gynecological cancer are inconsistent. Vitamin D supplementation has no effect on cancer incidence, although a modest reduction in cancer-related mortality has been observed. Concerning infections, vitamin D deficiency has been associated with acute respiratory tract infections, including coronavirus disease 2019 (COVID-19). Vitamin D supplementation may decrease the risk of acute respiratory tract infections and the severity of COVID-19 (not the risk of infection). Concerning menopausal symptomatology, vitamin D deficiency may have a negative impact on some aspects, such as sleep disturbances, depression, sexual function and joint pains. However, vitamin D supplementation has no effect on these, except for vulvovaginal atrophy, at relatively high doses, i.e., 40,000-60,000 IU/week (1000-1500 IU/week) orally or 1000 IU/day (25 μg/day) as a vaginal suppository.

Vitamin D, Menopausal Health and COVID-19: Critical Appraisal of Current Data

Inconsistency exists across studies conducted in postmenopausal women regarding the effect of vitamin D deficiency (VDD) and supplementation on several aspects of menopausal health, such as fractures, vasomotor symptomatology, cardiovascular disease (CVD), cancer and infections, including coronavirus disease 2019 (COVID-19). The aim of this review is to critically summarize the evidence provided by observational studies and randomized controlled trials (RCTs) of vitamin D supplementation in postmenopausal women with VDD. Observational studies have found that VDD is associated with an increased risk of falls and fractures after the menopause. VDD also has a negative effect on menopausal symptomatology. VDD, especially its severe form, is associated with an increased risk of CVD risk factors and CVD events. VDD is associated with increased risk and mortality from several cancer types and risk of infections. The evidence from RCTs regarding the effect of vitamin D supplementation on falls, fractures, menopausal symptoms, cardiovascular disease, cancer and infections is not robust. Thus, skeletal health may benefit only when vitamin D is co-administered with calcium, especially in those ≥70 years old and with severe VDD. There is no evidence of a favorable effect on menopausal symptoms or risk of CVD or cancer, except for a modest reduction in cancer-related mortality. Inconsistency still exists regarding its effect on infection risk, disease severity and mortality due to COVID-19.

Vitamin D Deficiency Increases Mortality Risk in the UK Biobank : A Nonlinear Mendelian Randomization Study

BACKGROUND

Low vitamin D status is associated with increased mortality, but randomized trials on severely deficient participants are lacking.

OBJECTIVE

To assess genetic evidence for the causal role of low vitamin D status in mortality.

DESIGN

Nonlinear Mendelian randomization analyses.

SETTING

UK Biobank, a large-scale, prospective cohort from England, Scotland, and Wales with participants recruited between March 2006 and July 2010.

PARTICIPANTS

307 601 unrelated UK Biobank participants of White European ancestry (aged 37 to 73 years at recruitment) with available measurements of 25-hydroxyvitamin D (25-(OH)D) and genetic data.

MEASUREMENTS

Genetically predicted 25-(OH)D was estimated using 35 confirmed variants of 25-(OH)D. All-cause and cause-specific mortality (cardiovascular disease [CVD], cancer, and respiratory) were recorded up to June 2020.

RESULTS

There were 18 700 deaths during the 14 years of follow-up. The association of genetically predicted 25-(OH)D with all-cause mortality was L-shaped (P for nonlinearity < 0.001), and risk for death decreased steeply with increasing concentrations until 50 nmol/L. Evidence for an association was also seen in analyses of mortality from cancer, CVD, and respiratory diseases (P ≤ 0.033 for all outcomes). Odds of all-cause mortality in the genetic analysis were estimated to increase by 25% (odds ratio, 1.25 [95% CI, 1.16 to 1.35]) for participants with a measured 25-(OH)D concentration of 25 nmol/L compared with 50 nmol/L.

LIMITATIONS

Analyses were restricted to a White European population. A genetic approach is best suited to providing proof of principle on causality, whereas the strength of the association is approximate.

CONCLUSION

Our study supports a causal relationship between vitamin D deficiency and mortality. Additional research needs to identify strategies that meet the National Academy of Medicine's guideline of greater than 50 nmol/L and that reduce the premature risk for death associated with low vitamin D levels.

PRIMARY FUNDING SOURCE

National Health and Medical Research Council.

Role of vitamin D supplementation in the management of musculoskeletal diseases: update from an European Society of Clinical and Economical Aspects of Osteoporosis, Osteoarthritis and Musculoskeletal Diseases (ESCEO) working group

Vitamin D is a key component for optimal growth and for calcium-phosphate homeostasis. Skin photosynthesis is the main source of vitamin D. Limited sun exposure and insufficient dietary vitamin D supply justify vitamin D supplementation in certain age groups. In older adults, recommended doses for vitamin D supplementation vary between 200 and 2000 IU/day, to achieve a goal of circulating 25-hydroxyvitamin D (calcifediol) of at least 50 nmol/L. The target level depends on the population being supplemented, the assessed system, and the outcome. Several recent large randomized trials with oral vitamin D regimens varying between 2000 and 100,000 IU/month and mostly conducted in vitamin D-replete and healthy individuals have failed to detect any efficacy of these approaches for the prevention of fracture and falls. Considering the well-recognized major musculoskeletal disorders associated with severe vitamin D deficiency and taking into account a possible biphasic effects of vitamin D on fracture and fall risks, an European Society for Clinical and Economic Aspects of Osteoporosis, Osteoarthritis and Musculoskeletal Diseases (ESCEO) working group convened, carefully reviewed, and analyzed the meta-analyses of randomized controlled trials on the effects of vitamin D on fracture risk, falls or osteoarthritis, and came to the conclusion that 1000 IU daily should be recommended in patients at increased risk of vitamin D deficiency. The group also addressed the identification of patients possibly benefitting from a vitamin D loading dose to achieve early 25-hydroxyvitamin D therapeutic level or from calcifediol administration.

Justification of research using systematic reviews continues to be inconsistent in clinical health science-A systematic review and meta-analysis of meta-research studies

BACKGROUND

Redundancy is an unethical, unscientific, and costly challenge in clinical health research. There is a high risk of redundancy when existing evidence is not used to justify the research question when a new study is initiated. Therefore, the aim of this study was to synthesize meta-research studies evaluating if and how authors of clinical health research studies use systematic reviews when initiating a new study.

METHODS

Seven electronic bibliographic databases were searched (final search June 2021). Meta-research studies assessing the use of systematic reviews when justifying new clinical health studies were included. Screening and data extraction were performed by two reviewers independently. The primary outcome was defined as the percentage of original studies within the included meta-research studies using systematic reviews of previous studies to justify a new study. Results were synthesized narratively and quantitatively using a random-effects meta-analysis. The protocol has been registered in Open Science Framework (https://osf.io/nw7ch/).

RESULTS

Twenty-one meta-research studies were included, representing 3,621 original studies or protocols. Nineteen of the 21 studies were included in the meta-analysis. The included studies represented different disciplines and exhibited wide variability both in how the use of previous systematic reviews was assessed, and in how this was reported. The use of systematic reviews to justify new studies varied from 16% to 87%. The mean percentage of original studies using systematic reviews to justify their study was 42% (95% CI: 36% to 48%).

CONCLUSION

Justification of new studies in clinical health research using systematic reviews is highly variable, and fewer than half of new clinical studies in health science were justified using a systematic review. Research redundancy is a challenge for clinical health researchers, as well as for funders, ethics committees, and journals.

Definition, Assessment, and Management of Vitamin D Inadequacy: Suggestions, Recommendations, and Warnings from the Italian Society for Osteoporosis, Mineral Metabolism and Bone Diseases (SIOMMMS)

In the recent years, both the prescriptions of serum 25(OH)D levels assay, and vitamin D supplementation are constantly increasing, as well as the costs to be incurred relating to these specific aspects. As in many other countries, the risk of vitamin D deficiency is particularly high in Italy, as recently confirmed by cohort studies in the general population as well as in patients with metabolic bone disorder. Results confirmed the North-South gradient of vitamin D levels described among European countries, despite the wide use of supplements. Although vitamin D supplementation is also recommended by the Italian Medicine Agency for patients at risk for fragility fracture or for initiating osteoporotic medication, the therapeutic gap for osteoporosis in Italy is very high. There is a consistent proportion of osteoporotic patients not receiving specific therapy for osteoporosis following a fragility fracture, with a poor adherence to the recommendations provided by national guidelines and position paper documents. The failure or inadequate supplementation with vitamin D in patients on antiresorptive or anabolic treatment for osteoporosis is thought to further amplify the problem and exposes patients to a high risk of re-fracture and mortality. Therefore, it is important that attention to its possible clinical consequences must be given. Thus, in light of new evidence from the literature, the SIOMMMS board felt the need to revise and update, by a GRADE/PICO system approach, its previous original recommendations about the definition, prevention, and treatment of vitamin D deficiency in adults, released in 2011. Several key points have been here addressed, such as the definition of the vitamin D status: normality values and optimal values; who are the subjects considered at risk of hypovitaminosis D; opportunity or not of performing the biochemical assessment of serum 25(OH)D levels in general population and in subjects at risk of hypovitaminosis D; the need or not to evaluate baseline serum 25(OH)D in candidate subjects for pharmacological treatment for osteoporosis; how and whether to supplement vitamin D subjects with hypovitaminosis D or candidates for pharmacological treatment with bone active agents, and the general population; how and whether to supplement vitamin D in chronic kidney disease and/or chronic liver diseases or under treatment with drugs interfering with hepatic metabolism; and finally, if vitamin D may have toxic effects in the subject in need of supplementation.

Critical Appraisal of Large Vitamin D Randomized Controlled Trials

As a consequence of epidemiological studies showing significant associations of vitamin D deficiency with a variety of adverse extra-skeletal clinical outcomes including cardiovascular diseases, cancer, and mortality, large vitamin D randomized controlled trials (RCTs) have been designed and conducted over the last few years. The vast majority of these trials did not restrict their study populations to individuals with vitamin D deficiency, and some even allowed moderate vitamin D supplementation in the placebo groups. In these RCTs, there were no significant effects on the primary outcomes, including cancer, cardiovascular events, and mortality, but explorative outcome analyses and meta-analyses revealed indications for potential benefits such as reductions in cancer mortality or acute respiratory infections. Importantly, data from RCTs with relatively high doses of vitamin D supplementation did, by the vast majority, not show significant safety issues, except for trials in critically or severely ill patients or in those using very high intermittent vitamin D doses. The recent large vitamin D RCTs did not challenge the beneficial effects of vitamin D regarding rickets and osteomalacia, that therefore continue to provide the scientific basis for nutritional vitamin D guidelines and recommendations. There remains a great need to evaluate the effects of vitamin D treatment in populations with vitamin D deficiency or certain characteristics suggesting a high sensitivity to treatment. Outcomes and limitations of recently published large vitamin D RCTs must inform the design of future vitamin D or nutrition trials that should use more personalized approaches.

Vitamin D recommendations in clinical guidelines: A systematic review, quality evaluation and analysis of potential predictors

BACKGROUND

Vitamin D has been widely promoted for bone health through supplementation and fortification of the general adult population. However, there is growing evidence that does not support these strategies. Our aim is to review the quality and recommendations on vitamin D nutritional and clinical practice guidelines and to explore predictive factors for their direction and strength.

METHODS

We searched three databases and two guideline repositories from 2010 onwards. We performed a descriptive analysis, a quality appraisal using AGREE II scores (Appraisal of Guidelines Research and Evaluation) and a bivariate analysis evaluating the association between direction and strength of recommendations, AGREE II domains' scores and pre-specified characteristics.

RESULTS

We included 34 guidelines, 44.1% recommended, 26.5% suggested and 29.4% did not recommend vitamin D supplementation. Guidelines that scored higher for "editorial independence" and "overall quality score" were less likely to recommend or suggest vitamin D supplementation (median 68.8 vs 35.4; P = .001 and 58.3 vs 37.5; P = .02). Guidance produced by government organisations and those that reported source of funding were associated with higher AGREE II scores. Unclear role of source of funding was associated with recommending or suggesting vitamin D supplementation (P = .034). Editorial independence was an independent predictor for recommending or suggesting vitamin D supplementation (OR 1.09; CI95% 1.02 to 1.16; P = .006).

CONCLUSIONS

Policymakers, clinicians and patients should be aware that lower quality guidelines and those reporting conflicts of interest are more likely to promote vitamin D supplementation. Guideline organisations should improve the quality of their recommendations' development and the management of conflicts of interest. Users and editors should be aware of these findings when using and appraising guidelines.

Prevalence of biochemical osteomalacia in adults undergoing vitamin D testing

OBJECTIVE

Prolonged severe vitamin D deficiency can cause osteomalacia, but the 25-hydroxyvitamin D (25OHD) concentration below which this occurs is unknown. We investigated the prevalence of biochemical osteomalacia in adults with a measurement of 25OHD.

DESIGN, MEASUREMENT, AND PATIENTS

25OHD results between 1/1/2009 and 15/6/2020 were obtained from the regional laboratory database, together with measurements of serum calcium, parathyroid hormone (PTH) and alkaline phosphatase (ALP) within 6 months of the index 25OHD. We defined biochemical osteomalacia as all 3 of: albumin-adjusted serum calcium (aCa)<2.0 mmol/L, PTH>7.3 pmol/L and ALP>150 IU/L. Possible osteomalacia was 2/3 criteria with the other test not done. 25OHD measurements associated with significant renal impairment, elevated hepatic transaminases or hypercalcaemia were excluded.

RESULTS

110,046 25OHD measurements were identified over the 11.5 years period. After removal of ineligible measurements, 42,171 25OHD measurements from 32,386 individuals with at least 2 of aCa, PTH and ALP were included in analyses. Median 25OHD was 63 nmol/L; 8% were <25 nmol/L, and 33% were <50 nmol/L. Five index 25OHD measurements met the definition of biochemical osteomalacia, and another 11 were possible osteomalacia. After reviewing available clinical records for these 16 episodes, we classified 9 cases as osteomalacia and 7 as other diagnoses. Thus, the prevalence of biochemical osteomalacia was 0.02% (9/42,171) for 25OHD measurements and 0.23% (8/3432) for 25OHD<25 nmol/L. All cases of osteomalacia with 25OHD measurements prior to supplementation had 25OHD≤18 nmol/L.

CONCLUSION

The prevalence of biochemical osteomalacia is very low, even in individuals with 25OHD<25 nmol/L.

Future perspectives in addressing the global issue of vitamin D deficiency

Vitamin D is a fundamentally critical nutrient that the human body requires to function properly. It plays an important role in musculoskeletal health due to its involvement in the regulation of calcium and phosphorus. Having a low level of vitamin D in the body may be detrimental for a wide range of health outcomes, including risk of osteoporotic and stress fractures, risk of CVD and some cancers, and lowering of the capability of the immune system. Vitamin D is an unusual nutrient; it is not a vitamin, in the true sense of the word but a pro-hormone. The main source of vitamin D is UV exposure, not dietary intake. Interestingly, there are two forms of vitamin D, vitamin D2 and vitamin D3, both of which are metabolised into 25-hydroxyvitamin D (25(OH)D) in the liver, the biomarker of vitamin D status. Vitamin D deficiency is a global public health problem, especially amongst older people and ethnic minority groups. The newest publication from the UK Government's Public Health England Department recommends that vitamin D intake should be 10 μg daily and this recommendation compares well (albeit lower) with other guidelines such as the Institute of Medicine recommendation of 15 μg for those aged 1-70 years and 20 μg for those 70 years or over. Few countries, however, have a specific vitamin D policy to prevent deficiency in populations. Finland leads the way, demonstrating impressive results in reducing population-level vitamin D deficiency through mandatory food fortification programmes. Collaboration between academia, government and industry, including countries from varying latitudes, is essential to identify long-term solutions to the global issue of vitamin D deficiency. This paper provides a narrative review of the evidence related to the role of vitamin D deficiency in health outcomes, outlines controversies regarding setting levels of adequacy, identifies the prevalence of vitamin D deficiency across the globe, and identifies population-level strategies adopted by countries to prevent vitamin D deficiency.

Population vitamin D supplementation in UK adults: too much of nothing?

Topics for DTB review articles are selected by DTB's editorial board to provide concise overviews of medicines and other treatments to help patients get the best care. Articles include a summary of key points and a brief overview for patients. Articles may also have a series of multiple choice CME questions.

Vitamin D supplementation: much ado about nothing

The scientific interest and the number of papers dealing with vitamin D supplementation has greatly grown in the last decades. Unfortunately, expert consensus on many clinical aspects of this topic is still lacking. In addition, data coming from recent clinical trials and meta-analyses seem to strongly put into doubt the real benefit of vitamin D supplementation, on both skeletal and extra-skeletal outcomes. This is further confusing since they seem to completely contradict the considerable body of evidence provided from previous epidemiological studies. This paper aims to analyze these new data in order to shed light onto the debated issues.

Methodological quality of public health guideline recommendations on vitamin D and calcium : a systematic review protocol

INTRODUCTION

Current recommendations for vitamin D and calcium in dietary guidelines and bone health guidelines vary significantly among countries and professional organisations. It is unknown whether the methods used to develop these recommendations followed a rigourous process and how the differences in methods used may affect the recommended intakes of vitamin D and calcium. The objectives of this study are (1) collate and compare recommendations for vitamin D and calcium across guidelines, (2) appraise methodological quality of the guideline recommendations and (3) identify methodological factors that may affect the recommended intakes for vitamin D and calcium. This study will make a significant contribution to enhancing the methodological rigour in public health guidelines for vitamin D and calcium recommendations.

METHODS AND ANALYSES

We will conduct a systematic review to evaluate vitamin D and calcium recommendations for osteoporosis prevention in generally healthy middle-aged and older adults. Methodological assessment will be performed for each guideline against those outlined in the 2014 WHO handbook for guideline development. A systematic search strategy will be applied to locate food-based dietary guidelines and bone health guidelines indexed in various electronic databases, guideline repositories and grey literature from 1 January 2009 to 28 February 2019. Descriptive statistics will be used to summarise the data on intake recommendation and on proportion of guidelines consistent with the WHO criteria. Logistic regression, if feasible, will be used to assess the relationships between the methodological factors and the recommendation intakes.

ETHICS AND DISSEMINATION

Ethics approval is not required as we will only extract published data or information from the published guidelines. Results of this review will be disseminated through conference presentations and peer-reviewed publications.

PROSPERO REGISTRATION NUMBER

CRD42019126452.

Contribution of nutrition science to the vitamin D field-Clarity or confusion?

Recent opinion pieces have questioned whether nutrition science is fit for purpose, suggesting that the evidence-base for dietary recommendations is populated with poor quality science and unresolved controversy. Nutrition science is accused of not keeping up with the times and making little real-world progress to stem the growing global malnutrition crisis, by failing to apply cutting-edge techniques to nutrition problems. Nutritional epidemiology has been blamed for harming public health nutrition and the public perception of science itself, by selectively reporting biased, confounded data. Focussed on obesity and associated disorders and hunger, these articles do not refer to micronutrient deficiencies or advances in micronutrient research. There is a serious public health problem of low vitamin D status. Given that the field of vitamin D has experienced an exponential increase in peer-reviewed publications over the last 50 years, it seems timely that we take these cues to reflect upon whether the expanded body of scientific literature has contributed to a deeper knowledge of vitamin D in health and disease, leading to improved nutrition policy and patient care, or whether it has led to so much confusion and controversy that progress has been impeded. We consider whether the accusations of poor science and biased reporting levelled at nutrition science are evident within the vitamin D nutrition research area and whether they have compromised dietary recommendations for vitamin D. In evaluating whether reformation is required, we discuss the confusion and controversy within the field and signpost common ground within the vitamin D community. We outline vitamin D nutrition research that has presented strategies for vitamin D deficiency prevention within the population, particularly using food first approaches that could extend beyond high income settings to low- and middle-income countries. Finally, we encourage government and industry to implement technical advances and drive real-world progress.

Vitamin D testing and treatment: a narrative review of current evidence

Vitamin D testing and treatment is a subject of controversial scientific discussions, and it is challenging to navigate through the expanding vitamin D literature with heterogeneous and partially opposed opinions and recommendations. In this narrative review, we aim to provide an update on vitamin D guidelines and the current evidence on the role of vitamin D for human health with its subsequent implications for patient care and public health issues. Vitamin D is critical for bone and mineral metabolism, and it is established that vitamin D deficiency can cause rickets and osteomalacia. While many guidelines recommend target serum 25-hydroxyvitamin D (25[OH]D) concentrations of ≥50 nmol/L (20 ng/mL), the minimum consensus in the scientific community is that serum 25(OH)D concentrations below 25-30 nmol/L (10-12 ng/mL) must be prevented and treated. Using this latter threshold of serum 25(OH)D concentrations, it has been documented that there is a high worldwide prevalence of vitamin D deficiency that may require public health actions such as vitamin D food fortification. On the other hand, there is also reason for concern that an exploding rate of vitamin D testing and supplementation increases costs and might potentially be harmful. In the scientific debate on vitamin D, we should consider that nutrient trials differ from drug trials and that apart from the opposed positions regarding indications for vitamin D treatment we still have to better characterize the precise role of vitamin D for human health.

Assessment of research waste part 1: an exemplar from examining study design, surrogate and clinical endpoints in studies of calcium intake and vitamin D supplementation

BACKGROUND

Research waste is estimated to be very common, but assessments of its prevalence and scope are rare. As an example, we assessed research waste in clinical research on calcium intake (assessing study design and endpoint type) and vitamin D supplementation (assessing endpoint type).

METHODS

We examined 404 randomised controlled trials (RCTs) and observational studies of calcium intake (diet or supplements) and bone mineral density (BMD) or fracture, and 547 RCTs of vitamin D supplements, and assessed the proportion of studies that used surrogate or clinical endpoints. For studies with BMD or fracture as an endpoint, we estimated when the 'tipping' point occurred indicating the need for RCTs with fracture as an endpoint (based on cumulative meta-analyses of BMD RCTs, and chronological review of observational studies), and whether each study published at least 5y after the tipping point was novel, added new clinical knowledge or was research waste.

RESULTS

Observational studies of calcium intake and BMD or fracture outnumbered RCTs by 3.3-4.5 times. For both calcium intake and vitamin D supplements, studies using surrogate endpoints outnumbered studies using clinical endpoints by 1.6-3 times. Of 41 RCT publications of calcium intake and BMD or fracture published at least 5y after the tipping point in 1994, we considered that 19 (46%) lacked novelty, another 13 (32%) added no new clinical knowledge, and 30 (73%) were research waste. Of 204 observational study publications of calcium intake and BMD or fracture, 197 (96%) lacked novelty, another 5 (2%) added no new clinical knowledge, and 202 (99%) were research waste. Of 39 RCTs of vitamin D supplementation and BMD or fracture published at least 5y after the tipping point in 1999, 14 (36%) lacked novelty, another 13 (33%) added no new clinical knowledge, and 27 (69%) were research waste.

CONCLUSIONS

A high proportion of studies of calcium intake since 2000 (95%) and trials of vitamin D supplements since 2005 (69%) on BMD or fracture represent research waste.