Vitamin D supplementation: much ado about nothing

Consensus Statement on Vitamin D Status Assessment and Supplementation: Whys, Whens, and Hows

The 6th International Conference, "Controversies in Vitamin D," was convened to discuss controversial topics, such as vitamin D metabolism, assessment, actions, and supplementation. Novel insights into vitamin D mechanisms of action suggest links with conditions that do not depend only on reduced solar exposure or diet intake and that can be detected with distinctive noncanonical vitamin D metabolites. Optimal 25-hydroxyvitamin D (25(OH)D) levels remain debated. Varying recommendations from different societies arise from evaluating different clinical or public health approaches. The lack of assay standardization also poses challenges in interpreting data from available studies, hindering rational data pooling and meta-analyses. Beyond the well-known skeletal features, interest in vitamin D's extraskeletal effects has led to clinical trials on cancer, cardiovascular risk, respiratory effects, autoimmune diseases, diabetes, and mortality. The initial negative results are likely due to enrollment of vitamin D-replete individuals. Subsequent post hoc analyses have suggested, nevertheless, potential benefits in reducing cancer incidence, autoimmune diseases, cardiovascular events, and diabetes. Oral administration of vitamin D is the preferred route. Parenteral administration is reserved for specific clinical situations. Cholecalciferol is favored due to safety and minimal monitoring requirements. Calcifediol may be used in certain conditions, while calcitriol should be limited to specific disorders in which the active metabolite is not readily produced in vivo. Further studies are needed to investigate vitamin D effects in relation to the different recommended 25(OH)D levels and the efficacy of the different supplementary formulations in achieving biochemical and clinical outcomes within the multifaced skeletal and extraskeletal potential effects of vitamin D.

Post-diagnosis serum 25-hydroxyvitamin D concentrations in women treated for breast cancer participating in a lifestyle trial in Italy

OBJECTIVE

To report cross-sectionally serum levels of 25-hydroxyvitamin D [25(OH)D] in women living in Italy within 12 months from breast cancer (BC) diagnosis.

METHODS

Baseline data were obtained from 394 women diagnosed with primary BC, enrolled from 2016 to 2019 in a lifestyle trial conducted in Italy. Subjects' characteristics were compared between two 25(OH)D concentrations (hypovitaminosis D<20 and ≥20 ng/mL) with the Chi-squared test or Fisher's exact test for small-expected counts. Using multiple logistic regression-adjusted models, we estimated odds ratios (ORs) of hypovitaminosis D with 95% confidence intervals (CIs) in the total sample and in the unsupplemented subgroup.

RESULTS

Hypovitaminosis D was found in 39% of all subjects, 60% in unsupplemented subjects, and 10% in supplemented subjects. Increasing ORs of hypovitaminosis D were found with increasing body mass index, 25-30, >30, and ≥35 versus <25 kg/m2 (ORs: 2.50, 4.64, and 5.81, respectively, in the total cohort and ORs: 2.68, 5.38, and 7.08 in the unsupplemented); living in the most southern Italian region (OR 2.50, 95%CI 1.22-5.13); and with hypertriglyceridemia (OR 2.46; 95%CI 1.16-5.22), chemotherapy history (OR 1.86, 95%CI 1.03-3.38), and inversely with anti-estrogenic therapy (OR 0.43, 95%CI 0.24-0.75) in the total sample.

CONCLUSIONS

Hypovitaminosis D in women recently diagnosed with BC and participating in a lifestyle trial in Italy was widespread and highest with obesity, hypertriglyceridemia, and chemotherapy use. Considering that hypovitaminosis D is a risk factor for lower efficacy of bone density treatments and possibly BC mortality, our results suggest the need to promptly address and treat vitamin D deficiency.

Effects of Perceived Benefit on Vitamin D Supplementation Intention: A Theory of Planned Behaviour Perspective

There are many factors that affect vitamin D supplementation, including those from the theory of planned behaviour (TPB); however, how the perceived benefit acts in the model remains unknown. In the current study, we tested the efficacy of the TPB and the impacts of the perceived benefit (PBE) in the model. The subjects were 287 customers who purchased vitD from pharmacies in major cities in Taiwan. A structured questionnaire was used to collect the data. t-tests, analysis of variance (ANOVA), regression analyses, and path analysis via SPSS and AMOS were used to analyse the data. The original TPB model explained 47.5% of the variance of intention with the three variables of attitude (β = 0.261), perceived behavioural control (β = 0.183), and subjective norms (β = 0.169). The model that incorporated PBE increased the explained variance to 59.7%, and PBE became the strongest predictor (β = 0.310) and a significant mediator linking attitude, subjective norms, perceived control (ANC) with supplementation intention. PBE and attitude were the two most important variables in predicting vitD supplementation intention. We suggest that updated information regarding dietary sources of vitD and its benefits should be included in health- or nutrition-related courses in education programs for the overall health of the nation.

Calcium and vitamin D supplementation: when and why

Osteoporosis is a common disease, with fragility fractures representing its dreaded complications. The role of calcium and vitamin D supplementation needs to be addressed in the context of a heavy health burden, with a massive impact on individuals, healthcare systems, and societies as a whole. Calcium and vitamin D are often discussed together as interventions for promoting bone health. Still, it is essential to remember that they are quite distinct entities that play different roles in mineral metabolism. Insufficient calcium intake and vitamin D deficiency are common and widespread. Furthermore, a strong association between vitamin D deficiency and extra-skeletal outcomes has emerged over the last decades. When dietary intake is insufficient, with little room for improvement, several supplementation strategies have proved to be effective and safe. Adequate calcium intake and vitamin D serum levels should be pursued efficiently in the general population, and deficiency should be considered unacceptable in subsets particularly at risk. The aim of this narrative review was to present an overview of calcium and vitamin D intake and their supplementation.

Pharmacodynamics of Oral Cholecalciferol in Healthy Individuals with Vitamin D Deficiency: A Randomized Open-Label Study

Comparative pharmacodynamic (PD) analyses on different dosing schedules for cholecalciferol supplementation are limited. This was an open-label, randomized, parallel-group study involving 75 healthy individuals deficient in vitamin D (baseline 25OHD < 20 ng/mL) receiving oral cholecalciferol with three different dosing regimens: Group A: 10,000 IU/day for 8 weeks followed by 1000 IU/day for 4 weeks; Group B: 50,000 IU/week for 12 weeks and Group C: 100,000 IU every other week for 12 weeks. Regulators of calcium and phosphate homeostasis, bone turnover markers and Wnt inhibitors were measured at baseline, Day 28, 53, 84, and 112. The 1,25OH2D increased at each time point. The increase was greater (p < 0.05) for group A vs. B and C at Day 28, and vs. group B at Day 56. No significant difference among groups was observed for the other biomarkers. The 24,25OH2D remained stable over time. PTH decreased at Day 84 and FGF-23 increased at all time points. CTX-I and PINP increased slightly at Day 28. BALP decreased from Day 56 onward. Dkk-1 increased from Day 56 onward, while sclerostin did not show significant changes. In healthy individuals deficient in vitamin D, vitamin D supplementation exerted effects on multiple regulators of calcium, phosphate and bone metabolism, without marked differences using the three regimens.

Sunlight and health: shifting the focus from vitamin D3 to photobiomodulation by red and near-infrared light

Both sun exposure and serum vitamin D levels have been associated with lower risks of all-cause mortality and chronic age-related diseases, e.g., cancer, diabetes and cardiovascular disease, in epidemiological studies. These associations have mainly been ascribed to beneficial effects of vitamin D. However, a vast body of randomized controlled trials (RCTs) and Mendelian randomization studies have failed to confirm any major health benefits from vitamin D supplementation. In this review, we present tentative evidence showing that red and near-infrared light, both being present in sunlight, could explain the associations between sunlight exposure and better health status. Body irradiation with red and near-infrared light, usually termed as photobiomodulation (PBM), has demonstrated beneficial effects in animal models of chronic diseases. Beyond this, preliminary evidence from RCTs suggest potential clinical benefit from PBM for chronic diseases. PBM is currently being investigated in many pre-registered clinical trials, results of which will eventually clarify the role of red and near-infrared light in the prevention and treatment of common age-related chronic diseases.

Pharmacokinetics of Oral Cholecalciferol in Healthy Subjects with Vitamin D Deficiency: A Randomized Open-Label Study

BACKGROUND

the aim of this study was to investigate the pharmacokinetic (PK) and safety profile of high-dose vitamin D supplementation, comparing different schedules (daily, weekly, or bi-weekly) in an otherwise healthy vitamin D-deficient population. Methods: single-center, open-label study on healthy subjects deficient in vitamin D (25 (OH)D < 20 ng/mL), randomized to receive cholecalciferol (DIBASE^®, Abiogen Pharma, Italy) using three different schedules: Group A: 10,000 IU/day for eight weeks followed by 1000 IU/day for four weeks; Group B: 50,000 IU/week for 12 weeks, Group C: 100,000 IU/every other week for 12 weeks. Total cumulative doses were: 588,000 IU, 600,000 IU, 600,000 IU. The treatment regimens corresponded to the highest doses allowed for cholecalciferol for the correction of vitamin D deficiency in adults in Italy.

RESULTS

mean 25 (OH)D plasma levels significantly increased from baseline 13.5 ± 3.7 ng/mL to peak values of 81.0 ± 15.0 ng/mL in Group A, 63.6 ± 7.9 ng/mL in Group B and 59.4 ± 12 ng/mL in Group C. On day 28, all subjects showed 25 (OH)D levels ≥ 20 ng/mL and 93.1% had 25 (OH)D levels ≥ 30 ng/mL. On day 56 and 84, all subjects had 25 (OH)D levels ≥ 30 ng/mL. No serious adverse events occurred during the study.

CONCLUSIONS

normalization of 25 (OH)D serum levels was quickly attained with all the studied regimens. A more refracted schedule provided a higher systemic 25 (OH)D exposure.