Effectiveness and Safety of a High-Dose Weekly Vitamin D (20,000 IU) Protocol in Older Adults Living in Residential Care

Vitamin D deficiency in nursing home residents: a systematic review

CONTEXT

Vitamin D deficiency is a global public health issue, particularly in nursing home residents.

OBJECTIVE

This review critically summarizes the prevalence of vitamin D deficiency in nursing home residents worldwide. In addition, it outlines the effect of vitamin D intervention, alone or in combination with other nutrients or therapies, on improving vitamin D status and associated health outcomes in nursing home residents.

DATA SOURCES, EXTRACTION, AND ANALYSIS

Searches were conducted of electronic databases for articles published from 2010 to May 2021. After screening of the 366 papers initially identified, 58 articles were included.

CONCLUSIONS

A paucity of observational studies in nursing homes suggests a high prevalence of vitamin D deficiency ranging from 8% [25(OH)D <25 nmol/L], up to 94% [25(OH)D <50 nmol/L] in some cohorts where supplement use was low. Reported factors associated with deficiency and suboptimal vitamin D status include lack of sunlight exposure, poor dietary intake of vitamin D, limited vitamin D food fortification, frailty, poor renal function, and low use of vitamin D supplements. Residents who are severely deficient, deficient, or insufficient in vitamin D require remedial vitamin D supplementation prior to maintenance supplementation at doses >800 IU/day. High-dose vitamin D supplementation may reduce respiratory illness; however, supportive data are limited. Oral nutritional supplements, in combination with exercise, may benefit physical function and performance, whereas supplementation with vitamin D- and calcium-fortified foods has been associated with improved quality of life and reduced bone resorption. Globally, vitamin D deficiency is highly prevalent in nursing home residents. There is an urgent need for standardized dietary and supplementation guidelines to prevent deficiency in this vulnerable group.

Genetic, environmental and biomarker considerations delineating the regulatory effects of vitamin D on central nervous system function

Studies show that vitamin D (vit-D) (25(OH)D), the bioactive metabolite (1,25(OH)2D3) and vit-D receptors (vit-D receptor; protein disulphide isomerase, family A member 3) are expressed throughout the brain, particularly in regions pivotal to learning and memory. This has led to the paradigm that avoiding vit-D deficiency is important to preserve cognitive function. However, presently, it is not clear if the common clinical measure of serum 25(OH)D serves as a robust surrogate marker for central nervous system (CNS) homeostasis or function. Indeed, recent studies report CNS biosynthesis of endogenous 25(OH)D, the CNS expression of the CYP group of enzymes which catalyse conversion to 1,25(OH)2D3 and thereafter, deactivation. Moreover, in the periphery, there is significant ethnic/genetic heterogeneity in vit-D conversion to 1,25(OH)2D3 and there is a paucity of studies which have actually investigated vit-D kinetics across the cerebrovasculature. Compared with peripheral organs, the CNS also has differential expression of receptors that trigger cellular response to 1,25(OH)2D3 metabolites. To holistically consider the putative association of peripheral (blood) abundance of 25(OH)D on cognitive function, herein, we have reviewed population and genetic studies, pre-clinical and clinical intervention studies and moreover have considered potential confounders of vit-D analysis.

Adequate vitamin B12 and riboflavin status from menus alone in residential care facilities in the Lower Mainland, British Columbia

Older adults have potential increased risk of nutrient deficiencies because of age-related decreased dietary intake and malabsorption; it is important to ensure nutrient needs are met to avoid adverse health outcomes. B vitamins are of particular interest: vitamin B₁₂ deficiency can cause irreversible neurodegeneration; there is mandatory folic acid fortification in Canada; and suboptimal riboflavin status has been reported among older adults in the United Kingdom. In this exploratory secondary analysis study we assessed vitamin B₁₂ and riboflavin biochemical status (via microparticle enzyme immunoassay and erythrocyte glutathione reductase activity coefficient (EGRac), respectively), and the vitamin B₁₂, riboflavin, and folate content of menus served to a convenience sample of older adults (≥65 years) from 5 residential care facilities within the Lower Mainland of British Columbia, Canada. Diet was assessed from customized 28-day cycle meal plans. Participants (n = 207; 53 men and 154 women) were aged 86 ± 7 years, largely of European descent (92%), and nonsmokers (95%). The menus served had a low prevalence of inadequacy for vitamin B₁₂ and riboflavin (only 4% and 1% of menus contained less than the estimated average requirement (EAR), respectively), but 93% contained less than the EAR for folate. Mean ± SD serum total vitamin B₁₂ concentration was 422 ± 209 pmol/L, and EGRac was 1.30 ± 0.19. The majority of older adults in residential care were provided with adequate vitamin B₁₂ and riboflavin menu amounts, and only 5% were vitamin B₁₂ deficient (<148 pmol/L). However, 26% were riboflavin deficient (EGRac ≥ 1.4), which may warrant further investigation.

The vitamin D, ionised calcium and parathyroid hormone axis of cerebral capillary function: therapeutic considerations for vascular-based neurodegenerative disorders

Blood-brain barrier dysfunction characterised by brain parenchymal extravasation of plasma proteins may contribute to risk of neurodegenerative disorders, however the mechanisms for increased capillary permeability are not understood. Increasing evidence suggests vitamin D confers central nervous system benefits and there is increasing demand for vitamin D supplementation. Vitamin D may influence the CNS via modulation of capillary function, however such effects may be indirect as it has a central role in maintaining calcium homeostasis, in concert with calcium regulatory hormones. This study utilised an integrated approach and investigated the effects of vitamin D supplementation, parathyroid tissue ablation (PTX), or exogenous infusion of parathyroid hormone (PTH) on cerebral capillary integrity. Parenchymal extravasation of immunoglobulin G (IgG) was used as a marker of cerebral capillary permeability. In C57BL/6J mice and Sprague Dawley rats, dietary vitamin D was associated with exaggerated abundance of IgG within cerebral cortex (CTX) and hippocampal formation (HPF). Vitamin D was also associated with increased plasma ionised calcium (iCa) and decreased PTH. A response to dose was suggested and parenchymal effects persisted for up to 24 weeks. Ablation of parathyroid glands increased CTX- and HPF-IgG abundance concomitant with a reduction in plasma iCa. With the provision of PTH, iCa levels increased, however the PTH treated animals did not show increased cerebral permeability. Vitamin D supplemented groups and rats with PTH-tissue ablation showed modestly increased parenchymal abundance of glial-fibrillary acidic protein (GFAP), a marker of astroglial activation. PTH infusion attenuated GFAP abundance. The findings suggest that vitamin D can compromise capillary integrity via a mechanism that is independent of calcium homeostasis. The effects of exogenous vitamin D supplementation on capillary function and in the context of prevention of vascular neurodegenerative conditions should be considered in the context of synergistic effects with calcium modulating hormones.