Vitamin D, neurocognitive functioning and immunocompetence

Vitamin D and Aging: Central Role of Immunocompetence

The pro-hormone vitamin D3 is an important modulator of both innate and adaptive immunity since its biologically active metabolite 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3) regulates via the transcription factor VDR (vitamin D receptor) the epigenome and transcriptome of human immune cells and controls in this way the expression of hundreds of vitamin D target genes. Since the myeloid linage of hematopoiesis is epigenetically programmed by VDR in concert with the pioneer factors PU.1 (purine-rich box 1) and CEBPα (CCAAT/enhancer binding protein α), monocytes, macrophages, and dendritic cells are the most vitamin D-sensitive immune cell types. The central role of the immune system in various aging-related diseases suggests that immunocompetence describes not only the ability of an individual to resist pathogens and parasites but also to contest non-communicative diseases and the process of aging itself. In this review, we argue that the individual-specific responsiveness to vitamin D relates to a person's immunocompetence via the epigenetic programming function of VDR and its ligand 1,25(OH)2D3 during hematopoiesis as well as in the periphery. This may provide a mechanism explaining how vitamin D protects against major common diseases and, in parallel, promotes healthy aging.

Unprecedented effect of vitamin D3 on T-cell receptor beta subunit and alpha7 nicotinic acetylcholine receptor expression in a 3-nitropropionic acid induced mouse model of Huntington's disease

Introduction

3-NP induction in rodent models has been shown to induce selective neurodegeneration in the striatum followed by the cortex (Brouillet, 2014). However, it remains unclear whether, under such a neurotoxic condition, characterized by neuroinflammation and oxidative stress, the gene expression of the immune resident protein, T-cell receptor beta subunit (TCR-β), α7 nicotinic acetylcholine receptor (α7 nAChRs), the nuclear factor kappa B (NF-κB), inflammatory cytokines (TNF-α and IL-6), and antioxidants (Cat and GpX4) get modulated on Vitamin D3 (VD) supplementation in the central nervous system.

Methods

In the present study, real-time polymerase chain reaction (RT-PCR) was performed to study the expression of respective genes. Male C57BL/6 mice (8-12 weeks) were divided into four groups namely, Group I: Control (saline); Group II: 3-NP induction via i.p (HD); Group III: Vitamin D3 (VD) and Group IV: (HD + VD) (Manjari et al., 2022).

Results

On administration of 500IU/kg/day of VD, HD mice showed a significant reduction in the gene expression of the immune receptor, TCR-β subunit, nuclear factor kappa B (NF-κB), inflammatory cytokines, and key antioxidants, followed by a decrease in the acetylcholinesterase activity.

Conclusion

A novel neuroprotective effect of VD in HD is demonstrated by combating the immune receptor, TCR-β gene expression, antioxidant markers, and inflammatory cytokines. In addition, HD mice on VD administration for 0-15 days showed an enhancement in cholinergic signaling with restoration in α7 nAChRs mRNA and protein expression in the striatum and cortex.

Vitamin D and smell impairment: a systematic literature review

OBJECTIVE

Smell impairment affects 60-80 per cent of individuals aged over 80 years. This review aimed to identify any association between vitamin D deficiency and smell impairment, and determine the efficacy of vitamin D to treat smell impairment.

METHODS

A literature search was conducted across four databases between the years 2000 and 2022. The literature screen was performed by two independent reviewers.

RESULTS

Seven articles were included in this review. Four studies examined the association between vitamin D deficiency and smell impairment, with three studies identifying a significant relationship. Three studies investigated the use of vitamin D as treatment for smell impairment, which found complete resolution or significant symptom improvement after vitamin D deficiency was treated.

CONCLUSION

This review identified limited studies on this topic. As vitamin D supplementation is relatively cost-efficient, further large-scale studies should be carried out to investigate the efficacy of vitamin D for treating anosmia.

Association between Vitamin D and Cognitive Deficiency in Alcohol Dependence

There are still not enough findings to elucidate how exactly alcohol use impairs cognitive abilities. Some studies have shown that there is a link between alcohol intake and vitamin D levels, but these findings are inconsistent so further research is needed. The aim of this study was to investigate the association between serum vitamin D levels and cognitive impairment in alcohol-dependent individuals. A case-control study was carried out including a total of N = 132 respondents with a medical history of alcoholism, and healthy volunteers. The Montreal Cognitive Assessment (MoCa) and Addenbrooke’s Cognitive Examination-Revised (ACE-R) screening tools were used for cognitive status assessment and serum vitamin D levels analysis (blood samples of respondents). Significant difference (p = 0.022), was found in vitamin D levels in the alcohol-dependent group with cognitive deficiency 13.7 ± 9.4 (ng/mL), alcohol-dependent group without cognitive deficiency 19.5 ± 11.2 (ng/mL) and healthy controls 19.9 ± 11.1 (ng/mL), respectively. Furthermore, vitamin D levels were significantly different across all groups based on MoCa (p = 0.016) and ACE-R (p = 0.004) scores. All three groups exhibited vitamin D deficiency. A significant correlation was found between vitamin D deficiency and cognitive impairment, but it yielded no significant difference in alcohol-dependent individuals.

Effects of vitamin D in the nervous system: Special focus on interaction with steroid hormone signalling and a possible role in the treatment of brain cancer

The active vitamin D hormone, 1,25-dihydroxyvitamin D₃ , exerts many physiological actions in the body, including effects on the nervous system. Studies of steroidogenesis in cells of the nervous system and elsewhere not only indicate that 1,25-dihydroxyvitamin D₃ affects steroidogenic pathways but also suggest varying responses in different cell types. For example, 1,25-dihydroxyvitamin D₃ stimulates the expression of aromatase in human glioma but not in human neuroblastoma cells or rat astrocytes. However, in astrocytes, 1,25-dihydroxyvitamin D₃ suppresses 3β-hydroxysteroid dehydrogenase and steroid 17-hydroxylase/lyase. Other studies indicate cross-talk between vitamin D signalling and signalling of oestrogens, progesterone or glucocorticoids. Reported data indicate synergistic effects of combinations of 1,25-dihydroxyvitamin D₃ and other steroid hormones on neuroinflammation, neurite outgrowth and neuroprotection. Also, dysregulation of steroid pathways affecting brain cells is found in vitamin D deficiency. Thus, several studies suggest that active vitamin D may affect steroid hormone synthesis and/or signalling in the nervous system, although the potential mechanisms for these responses remain unclear. 1,25-Dihydroxyvitamin D₃ suppresses proliferation in several cell types and is therefore of interest in cancer treatment. Also, epidemiological studies associate vitamin D levels with cancer risk or outcomes. Reported data on tumours of the nervous system are mainly on glioma, a common type of brain cancer. Expression of the vitamin D receptor in glioma tumours is associated with improved survival. Several studies show that 1,25-dihydroxyvitamin D₃ and vitamin D analogues (synthetic vitamin D-like compounds) suppress proliferation and migration in human vitamin D receptor-expressing glioma cell lines. Studies on mechanisms for actions of 1,25-dihydroxyvitamin D₃ or its analogues indicate regulation of cell cycle proteins and senescence markers. These compounds also show synergism in combination with other cancer therapies treating glioma. From the data available, vitamin D analogues emerge as interesting candidates for the future improved treatment of human glioma and possibly also other cancers of the nervous system.

A Prospective Cohort Study of Vitamin D Supplementation in AD Soldiers: Preliminary Findings

PURPOSE

To explore response to vitamin D supplementation in active duty (AD) warfighters and translate findings into evidence-based health policy.

BACKGROUND

Soldiers are at risk for musculoskeletal injuries and metabolic dysfunction that impact physical performance and military readiness; the link with low vitamin D status is unclear.

METHODS

This prospective trial enrolled 152 soldiers; baseline 25 hydroxyvitamin (OH) D level determined assignment to a no-treatment control (CG) or treatment group (TG) receiving a vitamin D3 supplement for 90 days. Symptoms, diet, sun exposure, and blood biomarkers obtained at baseline (T1) and 3 months (T2).

RESULTS

Cohort was predominantly white (58%) with a significant difference in racial distribution for vitamin D status. Mean (SD) 25(OH)D levels were 37.8 (5.6) ng/mL, 22.2 (5.0) ng/mL, and 22.9 (4.7) ng/mL for the CG, low dose TG, and high-dose TG at T1, respectively. Following three months of treatment, one-way ANOVA indicated a statistically significant difference between groups (F5,246 = 44.37; p < 0.0001). Vitamin D intake was 44% of Recommended Dietary Allowance throughout the first phase of the trial. Patient-Reported Outcomes Measurement Information System scores improved in TG for fatigue and sleep, p < 0.01.

CONCLUSIONS

Vitamin D deficiency is widespread in AD soldiers. Clinicians must intervene early in preventable health conditions impacting warfighter performance and readiness and recommend appropriate self-care strategies.

The Relationship Between Serum Concentration of Vitamin D, Total Intracranial Volume, and Severity of Depressive Symptoms in Patients With Major Depressive Disorder

Background: Depression has been linked to vitamin D deficiency. However, little attention was paid to the neural substrate underlying this association. Methods: Fifty patients with major depressive disorder (MDD) were enrolled in this study. High-resolution structural magnetic resonance imaging was performed to calculate total intracranial volume (TIV). Peripheral venous blood samples were collected to measure serum vitamin D concentration. Hamilton Rating Scale for Depression (HAMD) was used to assess severity of depression symptoms. The relationship among TIV, serum vitamin D concentration, and HAMD score was examined using correlation, linear regression, and mediation analyses. Results: In patients with MDD, HAMD score was negatively correlated with TIV and serum vitamin D concentration, and TIV was positively correlated with serum vitamin D concentration. Linear regression analyses showed that TIV and serum vitamin D concentration were significant predictors of HAMD score. Importantly, mediation analysis revealed that TIV significantly mediated the relationship between serum vitamin D concentration and HAMD score. Conclusion: Our findings suggest that TIV may serve as a potential neural biomarker for monitoring responses to adjuvant therapy of vitamin D in patients with MDD.

Prevalence of Vitamin D Deficiency in Pediatric Patients With Scoliosis Preparing for Spinal Surgery

BACKGROUND

Establishing prevalence of vitamin D deficiency in elective scoliosis surgery may impact clinical outcomes. The objectives of this study were to document vitamin D status of patients with scoliosis preparing for surgical intervention in order to establish frequency of deficiency and determine characteristics influencing levels.

METHODS

Records were queried for patients with scoliosis diagnosis who underwent posterior spinal fusion or initial growing rod placement and had serum vitamin 25 hydroxyvitamin D (D25) recorded in the preoperative period. Demographic data (gender, age, body mass index [BMI], race, scoliosis type, spine surgery procedure, and season of the year) were extracted. Chi-square analysis and multivariate modeling were used to evaluate deficiency status among various demographic categories and determine the demographic factors impacting D25.

RESULTS

A total of 217 patients with a mean age of 13.6 ± 3.6 years had vitamin D levels drawn a mean of 38.7 ± 20.6 days prior to surgery. The majority of the sample presented with a diagnosis of idiopathic scoliosis (n = 126), and most patients were scheduled for spinal fusion surgery (n = 192). Nearly 75% of the study population (n = 162) demonstrated D25 values below normal. African Americans presented with greater risk of deficiency (p < .0002) compared to Caucasians, as did patients preparing for spinal fusion versus growing rod placement (p < .03). Severe hypovitaminosis D was more common in winter than any other season (p < .005). Patients with neuromuscular scoliosis demonstrated significantly higher D25 levels over the idiopathic diagnosis type (p < .0002). Gender, BMI, and age did not impact D25.

CONCLUSION

Low D25 levels are reported in pediatric patients with scoliosis preparing for corrective spinal surgery. Population subsets most at risk for deficiency in this limited study include African American children, those presenting for spinal fusion surgery, and patients admitted in winter season.

Vitamin D deficiency is associated with a poor prognosis in advanced non-small cell lung cancer patients treated with platinum-based first-line chemotherapy

OBJECTIVES

This study aimed to examine the prognostic role of the plasma 25-hydroxyvitamin D (25(OH)D) level in advanced non-small cell lung cancer (NSCLC) patients treated with platinum-based doublet first-line chemotherapy.

METHODS

A total of 195 advanced NSCLC patients were consecutively and prospectively hospitalized to receive platinum-based first-line chemotherapy. The baseline 25(OH)D level was measured at the time of diagnosis. Main outcome measures included overall survival (OS) and progression-free survival (PFS).

RESULTS

With 10 ng/mL as the cutoff value for the baseline plasma 25(OH)D level, patients with 25(OH)D < 10 ng/mL (n = 54) and those with 25(OH)D ≥ 10 ng/mL (n = 141) were found to have similar characteristics in terms of age, sex, smoking status, pathological type, Eastern Cooperative Oncology Group (ECOG) performance status, and clinical staging (all P-values > 0.05). The median OS values of patients with 25(OH)D < 10 ng/mL and ≥ 10 ng/mL were 17.9 months (95% confidence interval [CI], 14.4-21.4 months) and 20.8 months (95%CI, 17.9-23.8 months), respectively; the median PFS values were 9.4 months (95%CI, 8.2-10.5 months) and 9.4 months (95%CI, 8.3-10.5 months), respectively. Both univariate and multivariate analyses showed that having a plasma 25(OH)D level < 10 ng/mL was associated with a significantly shorter OS (P = 0.003; P = 0.009), while the baseline plasma 25(OH)D level was not significantly associated with PFS.

CONCLUSION

Deficiency of 25(OH)D is an independent prognostic factor for a poor OS in advanced NSCLC patients treated with platinum-based first-line chemotherapy.

Supplementation of docosahexaenoic acid (DHA), vitamin D3 and uridine in combination with six weeks of cognitive and motor training in prepubescent children: a pilot study

Background

Learning and memory have been shown to be influenced by combination of dietary supplements and exercise in animal models, but there is little available evidence from human subjects. The aim of this pilot study was to investigate the effect of combining a motor- and cognitive exercise program with dietary supplementation consisting of 500 mg docosahexaenoic acid (DHA), 10 μg vitamin D₃ and 1000 mg uridine (DDU-supplement) in 16 prepubescent children (age 8–11 years).

Methods

We designed a randomized, placebo-controlled, double-blinded study lasting 6 weeks in which DDU-supplement or placebo was ingested daily. During the intervention period, all children trained approximately 30 min 3 days/week using an internet-based cognitive and motor training program (Mitii). Prior to and post the intervention period dietary record, blood sampling, physical exercise tests and motor and cognitive tests were performed.

Results

Fourteen of the 16 children completed the intervention and ingested the supplement as required. 6 weeks DDU-supplementation resulted in a significant increase in the blood concentration of vitamin D₂₊₃ and DHA (p = 0.023 and p < 0.001, respectively). Power calculation based on one of the cognitive tasks revealed a proper sample size of 26 children.

Conclusion

All children showed improved performance in the trained motor- and cognitive tasks, but it was not possible to demonstrate any significant effects on the cognitive tests from the dietary supplementation. However, DDU-supplementation did result in increased blood concentration of DHA and vitamin D₂₊₃.

Trial registration

Clinical registration ID: NCT02426554 (clinical Trial.gov). January 2015 retrospectively registered.

The Relationship between Symptom Severity and Low Vitamin D Levels in Patients with Schizophrenia

Background

In recent years, the relationship between schizophrenia and environmental factors has come into prominence. This study investigated the relationship between vitamin D levels and the positive and negative symptoms of schizophrenia by comparing vitamin D levels between patients with schizophrenia and a healthy control group.

Methods

The study included 80 patients diagnosed with schizophrenia and 74 age- and sex-matched controls. The Scale for the Assessment of Negative Symptoms (SANS) and the Scale for the Assessment of Positive Symptoms (SAPS) were used to evaluate symptom severity. The 25-hydroxyvitamin D (25OHD) levels of all subjects both patients and healthy controls were analyzed in relation to measurements of symptom severity.

Results

There were no significant differences between the groups in terms of age, sex, or physical activity. Their mean 25OHD levels were also similar (23.46±13.98ng/mL for the patient group and 23.69±9.61ng/mL for the control group). But when patients with schizophrenia were grouped based on their vitamin D levels, the results indicated a statistically significant differences between their vitamin D levels and their total SANS, affective flattening, and total SAPS, bizarre behavior and positive formal thought disorder scores (p = 0.019, p = 0.004, p = 0.015, p = 0.009 and p = 0.019, respectively). There is a negative correlation between 25OHD levels and SANS total points (r = -0.232, p = 0.038); a negative correlation for attention points (r = -0.227, p = 0.044) and negative correlation with positive formal thoughts (r = -0.257, p = 0.021).

Conclusion

The results of this study show a relationship between lower levels of vitamin D and the occurrence of positive and negative symptoms, along with increased severity of symptoms at lower levels of vitamin D, suggesting that treatment for schizophrenia should include assessment of patients’ vitamin D levels. We recommend that patients with schizophrenia should be assessed with regard to their vitamin D levels.

Investigation of Bone Health Subsequent to Vitamin D Supplementation in Children Following Burn Injury

BACKGROUND

The effect of supplemental vitamin D on fracture occurrence following burn injuries is unclear. The objective of this study was to evaluate postintervention incidence of fractures in children during the rehabilitative phase postburn (PB) following participation in a randomized clinical trial of vitamin D supplementation.

MATERIALS AND METHODS

Follow-up for fracture evaluation was obtained in 39 of 50 patients randomized to daily enteral vitamin D2, D3, or placebo throughout the acute burn course. Serum 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, D2, D3, calcitonin, and bone alkaline phosphatase (BAP) measurements were obtained PB day 7, midpoint, discharge, and 1-year PB. Urinary calcium was obtained PB day 7 and midpoint. Dual-energy x-ray absorptiometry (DXA) was performed at discharge and 1-year PB.

RESULTS

Fractures were reported in 6 of 39 respondents. Four fractures occurred in the placebo group, 2 in the D2 group, and none in the D3 group. Serum vitamin D, calcitonin, BAP, and urinary calcium were similar between fracture groups. The group with fracture morbidity had larger burn size (83.8% ± 4.9% vs 53.0% ± 2.9%, P < .0001), greater full-thickness burn (69.7% ± 9.4% vs 39.4% ± 4.1%, P = .02), and increased incidence of inhalation injury (33% vs 6%, P = .04). Decreased bone mineral density z score was noted at discharge in the placebo fracture compared with no-fracture group (P < .05).

CONCLUSION

This preliminary report suggests there may be benefit of vitamin D3 in reducing postdischarge fracture risk. Results reaffirm the importance of monitoring bone health in pediatric patients postburn.

Single-micronutrient and broad-spectrum micronutrient approaches for treating mood disorders in youth and adults

Several different vitamins and minerals appear to be effective augmenting agents for mood-modifying drugs, but are not potent monotherapies in themselves for treating psychiatric disorders. In contrast, broad-spectrum micronutrient interventions appear in early trials to be as effective as psychiatric medications with fewer adverse effects for treating mood disorders, ADHD, aggressivity, and misconduct in youth and adults. Broad-spectrum treatments also may improve stress responses, cognition, and sense of well-being in healthy adults, but have been less well studied in youth. Current clinical data justify an extensive expansion of research on micronutrient mechanisms and treatments in psychiatry.

Vitamin D and neurocognitive function

In recent years, emerging evidence has linked vitamin D not only to its known effects on calcium and bone metabolism, but also to many chronic illnesses involving neurocognitive decline. The importance of vitamin D₃ in reducing the risk of these diseases continues to increase due to the fact that an increasing portion of the population in developed countries has a significant vitamin D deficiency. The older population is at an especially high risk for vitamin D deficiency due to the decreased cutaneous synthesis and dietary intake of vitamin D. Recent studies have confirmed an association between cognitive impairment, dementia, and vitamin D deficiency. There is a need for well-designed randomized trials to assess the benefits of vitamin D and lifestyle interventions in persons with mild cognitive impairment and dementia.

The role of vitamin D in pathophysiology and treatment of fibromyalgia

Recent studies showed that most cells have receptors and enzymes responsible for metabolism of vitamin D. Several diseases have been linked to vitamin D deficiency, such as hypertension, diabetes, depression, Alzheimer's disease, Parkinson's disease, multiple sclerosis, and chronic pain syndromes such as fibromyalgia. The association between fibromyalgia and vitamin D deficiency is very controversial in the literature with conflicting studies and methodological problems, which leads to more questions than answers. The purpose of this article is to raise questions about the association of hypovitaminosis D with fibromyalgia considering causal relationships, treatment, and pathophysiological explanations.

Hypovitaminosis D in Delirium: a Retrospective Cross-sectional Study

Background

As vitamin D may have a neuroprotective effect, the authors studied the association of biomarkers of vitamin D status and delirium to see if low vitamin D status was common in delirium cases.

Methods

Biochemical measures of vitamin D (25-hydroxyvitamin D [25-OHD]) and calcium metabolism were used in this retrospective cross-sectional analysis of adult in-patients with delirium, admitted at three Canadian academic hospitals from January 2011 to July 2012. Primary outcome was to determine estimates of the prevalence of hypovitaminosis D in this group in whom vitamin D was checked.

Results

Seventy-one (5.8%) out of 1,232 delirium inpatients had their vitamin D measured. Thirty-nine (55%) showed vitamin D insufficiency (25-OHD of 25-75 nmol/L) and 8 (11%) showed vitamin D deficiency (25-OHD < 25 nmol/L). Mean serum 25-OHD levels were lower in males (57.1±7.7 nmol/L) than in females (78.2±6.1 nmol/L), p = .01, even when controlled for age and season. Men were younger than the women (74.4±2.3 vs. 82.4±1.7, p = .005). Mean age was 78.7±1.5 years, and 33 (47%) were male.

Conclusions

Although vitamin D is rarely checked during delirium workup and/or management, high rates of hypovitaminosis D were found to be common in the delirium in-patients in whom it was checked. Larger studies would be needed to estimate the prevalence of hypovitaminosis D in delirium and whether hypovitaminosis D plays a role in the pathogenesis of delirium.

A possible correlation between vitamin D deficiency and loss of smell: 2 case reports

OBJECTIVE

The purpose of this report is to present 2 cases of diminished olfaction that improved with increasing serum levels of vitamin D3.

CLINICAL FEATURES

Both patients were under the care of medical and chiropractic physicians for various complaints. A 47-year-old hyposmic woman was diagnosed with vitamin D deficiency who incidentally noticed a progressive return of her sense of smell while taking vitamin D supplements as prescribed by her medical doctor. A 34-year-old anosmic woman noticed a direct relationship with her ability to smell and vitamin D3 supplementation.

INTERVENTION AND OUTCOME

Treatment for the first patient consisted of vitamin D supplementation of 10 000 IU a day. Her serum D3 levels increased substantially over a period of 8 months, at which time she reported a marked improvement in her sense of smell. The second patient was prescribed 50 000 IU of vitamin D a week; and she reported an increased ability to smell, although only the strongest of odors.

CONCLUSION

A link between hypovitaminosis D and a diminished sense of smell was noted in these 2 individuals.

The transcriptomic response of mixed neuron-glial cell cultures to 1,25-dihydroxyvitamin d3 includes genes limiting the progression of neurodegenerative diseases

Seasonal or chronic vitamin D deficiency and/or insufficiency is highly prevalent in the human population. Receptors for 1,25-dihydroxyvitamin D3, the hormonal metabolite of vitamin D, are found throughout the brain. To provide further information on the role of this hormone on brain function, we analyzed the transcriptomic profiles of mixed neuron-glial cell cultures in response to 1,25-dihydroxyvitamin D3. 1,25-dihydroxyvitamin D3 treatment increases the mRNA levels of 27 genes by at least 1.9 fold. Among them, 17 genes were related to neurodegenerative and psychiatric diseases, or brain morphogenesis. Notably, 10 of these genes encode proteins potentially limiting the progression of Alzheimer's disease. These data provide support for a role of 1,25-dihydroxyvitamin D3 in brain disease prevention. The possible consequences of circannual or chronic vitamin D insufficiencies on a tissue with a low regenerative potential such as the brain should be considered.

Sunlight and Vitamin D: A global perspective for health

Vitamin D is the sunshine vitamin that has been produced on this earth for more than 500 million years. During exposure to sunlight 7-dehydrocholesterol in the skin absorbs UV B radiation and is converted to previtamin D3 which in turn isomerizes into vitamin D3. Previtamin D3 and vitamin D3 also absorb UV B radiation and are converted into a variety of photoproducts some of which have unique biologic properties. Sun induced vitamin D synthesis is greatly influenced by season, time of day, latitude, altitude, air pollution, skin pigmentation, sunscreen use, passing through glass and plastic, and aging. Vitamin D is metabolized sequentially in the liver and kidneys into 25-hydroxyvitamin D which is a major circulating form and 1,25-dihydroxyvitamin D which is the biologically active form respectively. 1,25-dihydroxyvitamin D plays an important role in regulating calcium and phosphate metabolism for maintenance of metabolic functions and for skeletal health. Most cells and organs in the body have a vitamin D receptor and many cells and organs are able to produce 1,25-dihydroxyvitamin D. As a result 1,25-dihydroxyvitamin D influences a large number of biologic pathways which may help explain association studies relating vitamin D deficiency and living at higher latitudes with increased risk for many chronic diseases including autoimmune diseases, some cancers, cardiovascular disease, infectious disease, schizophrenia and type 2 diabetes. A three-part strategy of increasing food fortification programs with vitamin D, sensible sun exposure recommendations and encouraging ingestion of a vitamin D supplement when needed should be implemented to prevent global vitamin D deficiency and its negative health consequences.

Vitamin D, cognition, and dementia: a systematic review and meta-analysis

OBJECTIVE

To examine the association between cognitive function and dementia with vitamin D concentration in adults.

METHODS

Five databases were searched for English-language studies up to August 2010, and included all study designs with a comparative group. Cognitive function or impairment was defined by tests of global or domain-specific cognitive performance and dementia was diagnosed according to recognized criteria. A vitamin D measurement was required. Two authors independently extracted data and assessed study quality using predefined criteria. The Q statistic and I² methods were used to test for heterogeneity. We conducted meta-analyses using random effects models for the weighted mean difference (WMD) and Hedge's g.

RESULTS

Thirty-seven studies were included; 8 contained data allowing mean Mini-Mental State Examination (MMSE) scores to be compared between participants with vitamin D <50 nmol/L to those with values ≥50 nmol/L. There was significant heterogeneity among the studies that compared the WMD for MMSE but an overall positive effect for the higher vitamin D group (1.2, 95% confidence interval [CI] 0.5 to 1.9; I² = 0.65; p = 0.002). The small positive effect persisted despite several sensitivity analyses. Six studies presented data comparing Alzheimer disease (AD) to controls but 2 utilized a method withdrawn from commercial use. For the remaining 4 studies the AD group had a lower vitamin D concentration compared to the control group (WMD = -6.2 nmol/L, 95% CI -10.6 to -1.8) with no heterogeneity (I² < 0.01; p = 0.53).

CONCLUSION

These results suggest that lower vitamin D concentrations are associated with poorer cognitive function and a higher risk of AD. Further studies are required to determine the significance and potential public health benefit of this association.

Subclinical vitamin D deficiency

The optimal vitamin D status, as defined by serum 25-hydroxyvitamin D [25(OH)D], is still controversial. Some individuals are at risk for subclinical vitamin D deficiency, as defined by serum 25(OH)D levels between 25 and 75 nmol/L, and up to 80-100% of the entire population can display inadequate serum 25(OH)D values depending on latitude and seasonality. The clinical manifestation of extreme vitamin D deficiency, i.e. rickets and osteomalacia, are rare. Levels of 25(OH)D ≥ 50 nmol/L are required for optimal musculoskeletal health. However, levels of 25(OH)D above 75 nmol/L may be necessary to maximize musculoskeletal benefits and take advantage of the extraskeletal actions of vitamin D. This review will summarize the actual positions on the boundaries of subclinical vitamin D deficiency, the main available evidence on the effects of inadequate vitamin D status on skeletal and extraskeletal targets and supplementation strategies.

Effect of vitamin D3 supplementation on relapses, disease progression, and measures of function in persons with multiple sclerosis: exploratory outcomes from a double-blind randomised controlled trial

BACKGROUND

High vitamin D levels may reduce the risk of relapses and disease progression in multiple sclerosis.

METHODS

This 96-week randomised controlled trial was designed to assess the effect of vitamin D(3) supplementation on bone mineral density in persons with multiple sclerosis. Supplementation with 20,000 IU vitamin D(3) weekly raised median serum 25-hydroxy vitamin D (25[OH]D) to 121 nmol/L. The modified intention to treat analysis included 35 persons in the vitamin D(3) group and 33 in the placebo group. Participants were age 21 to 50 years and fully ambulatory (median Expanded Disability Status Scale (EDSS) 2.5). We studied the effect of supplementing vitamin D(3) on the exploratory outcomes annualised relapse rate (ARR), EDSS, multiple sclerosis functional composite (MSFC) components, grip strength, and fatigue.

RESULTS

After 96 weeks, there was no significant difference between groups in ARR (absolute difference 0.10, 95% CI -0.07 to 0.27; p = 0.25), EDSS (absolute difference -0.01, 95% CI -0.35 to 0.35; p = 0.97), MSFC components, grip strength, or fatigue.

CONCLUSION

Supplementation with 20,000 IU vitamin D(3) weekly did not result in beneficial effects on the measured multiple sclerosis-related outcomes. This study was not powered to address clinical outcomes, but none of the results were suggestive of an effect in this unselected population of fully ambulatory persons with multiple sclerosis.

Toward a comprehensive differential diagnosis and clinical approach to fatigue in the elderly

This article provides primary care physicians with an encompassing approach to fatigue to help generate a comprehensive differential diagnosis. Two-thirds of patients with fatigue will have an identifiable cause that can be elucidated with a careful history and appropriate laboratory tests. Accordingly, a wide range of differential diagnoses is presented.

Vitamin D, cognitive dysfunction and dementia in older adults

The physiologically active form of vitamin D, 1,25-dihydroxyvitamin D(3), is a fat-soluble steroid hormone with a well established role in skeletal health. A growing body of evidence suggests low vitamin D levels also play a role in the pathogenesis of a wide range of non-skeletal, age-associated diseases including cancer, heart disease, type 2 diabetes mellitus and stroke. Low levels of serum 25-hydroxyvitamin D [25(OH)D], a stable marker of vitamin D status, are also associated with increased odds of prevalent cognitive dysfunction, Alzheimer's disease and all-cause dementia in a number of studies, raising the possibility that vitamin D plays a role in the aetiology of cognitive dysfunction and dementia. To date, the majority of human studies reporting associations between vitamin D and cognition or dementia have been cross-sectional or case-control designs that do not permit us to exclude the possibility that such associations are a result of disease progression rather than being causal. Animal and in vitro experiments have identified a number of neuroprotective mechanisms that might link vitamin D status to cognitive dysfunction and dementia, including vasoprotection and amyloid phagocytosis and clearance, but the clinical relevance of these mechanisms in humans is not currently clear. Two recent, large, prospective studies go some way to establish the temporal relationship with cognitive decline. The relative risk of cognitive decline was 60% higher (relative risk = 1.6, 95% CI 1.2, 2.0) in elderly Italian adults with severely deficient 25(OH)D levels (<25 nmol/L) when compared with those with sufficient levels (≥75 nmol/L). Similarly, the odds of cognitive decline were 41% higher (odds ratio = 1.4, 95% CI 0.9, 2.2) when elderly US men in the lowest quartile (≤49.7 nmol/L) were compared with those in the highest quartile (≥74.4 nmol/L). To our knowledge, no prospective studies have examined the association between 25(OH)D levels and incident dementia or neuroimaging abnormalities. The possible therapeutic benefits of vitamin D have attracted considerable interest as over 1 billion people worldwide are thought to have insufficient 25(OH)D levels and these levels can be increased using inexpensive and well tolerated dietary supplements. However, no large randomized controlled trials have yet examined the effect of vitamin D supplements on cognitive decline or incident dementia. Further studies are urgently needed to establish which mechanisms have clinical relevance in human populations and whether vitamin D supplements are effective at minimizing cognitive decline or preventing dementia.