Report on the vitamin D status of adult and pediatric patients with inflammatory bowel disease and its significance for bone health and disease

Dynamics of vitamin D in patients with mild or inactive inflammatory bowel disease and their families

BACKGROUND

25(OH) vitamin D levels may be low in patients with moderately or severely active inflammatory bowel diseases (IBD: Crohn's disease and Idiopathic Ulcerative Colitis) but this is less clear in patients with mild or inactive IBD. Furthermore there is limited information of any family influence on 25(OH) vitamin D levels in IBD. As a possible risk factor we hypothesize that vitamin D levels may also be low in families of IBD patients.

OBJECTIVES

To evaluate 25[OH] vitamin D levels in patients with IBD in remission or with mild activity. A second objective is to evaluate whether there are relationships within IBD family units of 25[OH] vitamin D and what are the influences associated with these levels.

METHODS

Participants underwent medical history, physical examination and a 114 item diet questionnaire. Serum 25[OH] vitamin D was measured, using a radioimmunoassay kit, (replete ≥ 75, insufficient 50-74, deficient < 25-50, or severely deficient < 25 nmol/L). Associations between 25[OH] vitamin D and twenty variables were evaluated using univariate regression. Multivariable analysis was also applied and intrafamilial dynamics were assessed.

RESULTS

55 patients and 48 controls with their respective families participated (N206). 25[OH] vitamin D levels between patients and controls were similar (71.2 ± 32.8 vs. 68.3 ±26.2 nmol/L). Vitamin D supplements significantly increased intake but correlation with serum 25[OH] vitamin D was significant only during non sunny months among patients. Within family units, patients' families had mean replete levels (82.3 ± 34.2 nmol/L) and a modest correlation emerged during sunny months between patients and family (r2 =0.209 p = 0.032). These relationships were less robust and non significant in controls and their families.

CONCLUSIONS

In patients with mild or inactive IBD 25[OH] vitamin D levels are less than ideal but are similar to controls. Taken together collectively, the results of this study suggest that patient family dynamics may be different in IBD units from that in control family units. However contrary to the hypothesis, intra familial vitamin D dynamics do not pose additional risks for development of IBD.

Changing incidence of inflammatory bowel disease: environmental influences and lessons learnt from the South asian population

Inflammatory bowel disease (IBD) is a chronic relapsing inflammatory disorder of the gastrointestinal tract associated with significant morbidity. While IBD occurs in genetically susceptible individuals, the etiology is multifactorial, involving environmental influences, intestinal dysbiosis, and altered immune responses. The rising incidence of IBD in industrialized countries and the emergence of IBD in countries with traditionally low prevalence underscore the importance of environmental influences in the pathobiology of the disease. Moreover the high incidence of IBD observed in the South Asian immigrant population in the United Kingdom and Canada further supports the influence of environmental factors.

High and increasing prevalence of inflammatory bowel disease in Finland with a clear North-South difference

BACKGROUND AND AIM

Inflammatory bowel disease (IBD) prevalence has increased and a North-South gradient has been reported. We estimated the nationwide prevalence of IBD, ulcerative colitis (UC) and Crohn's disease (CD) in 1993, and prevalence of IBD in 2008, and assessed the geographical distribution of IBD in Finland. In addition, we investigated the vitamin D levels in a study population from a large, nationally representative health examination survey, the Health 2000 Survey.

METHODS

The register study for prevalences included all patients who had special reimbursement of medications for IBD in the years 1993 (n=10,958) and 2008 (31,703). The study for D-vitamin measurement consisted of 6134 persons who had participated in the Health 2000 Survey.

RESULTS

The nationwide point prevalence of IBD in 1993 was 216 per 100,000 inhabitants, and 595 in 2008. In 1993, the prevalence of UC (177) was fourfold higher than the prevalence of CD (38). The prevalence of IBD and UC in Finland increased from South to North. For CD, no geographical variation could be demonstrated. In the Health 2000 survey, vitamin D levels were lower in Northern than in Southern Finland.

CONCLUSIONS

Finland belongs to high prevalence area of IBD and this prevalence has increased nearly threefold during the past 15 years. A clear North-South gradient has been shown for IBD and UC, but not for CD. Slightly lower vitamin D levels in Northern Finland may be associated with the observed higher prevalence of IBD there.

Vitamin d deficiency is associated with ulcerative colitis disease activity

PURPOSE

Previous studies on experimental mouse models have suggested a role of vitamin D in immune system regulation and IBD disease severity. In this study, we examine the relationship between vitamin D levels and clinical disease activity in human subjects with ulcerative colitis (UC). We hypothesized that patients with vitamin D deficiency will display increased UC disease activity as compared to patients with normal vitamin D levels.

METHODS

A cross-sectional study was performed by querying the outpatient electronic medical record of our health system for patients seen in the gastroenterology clinic from January 2007 to October 2009 who carried both a diagnosis of UC and a documented 25-OH vitamin D level within 30 days of their clinic visit. Demographic and clinical variables were collected. Clinical disease activity was calculated using the six-point partial Mayo index. Active disease was defined as a six-point index score of ≥ 1. Vitamin D deficiency was defined as a 25-OH D level below 30 ng/ml. Data were analyzed using the chi-square distribution test.

RESULTS

Thirty-four patients met inclusion criteria (53 % female, mean age 45.7 ± 24.7 years). Fifteen patients had normal vitamin D levels and 19 patients were vitamin D deficient. Twelve patients had vitamin D levels <20 ng/ml. Vitamin D deficient patients were statistically more likely to have increased disease activity than patients with normal vitamin D levels (p = 0.04), with 68 % of deficient patients displaying active disease compared with 33 % in the sufficient group. There was also a statistically significant association between vitamin D status and need for treatment with steroids, with a higher percentage of vitamin D deficient patients (47 %) requiring such treatment compared with 7 % in the sufficient group (p = 0.02). There was no association between season of visit and disease activity.

CONCLUSION

Vitamin D deficiency is common among patients with active UC, particularly those requiring corticosteroids. Further investigation is needed to determine the clinical utility of vitamin D monitoring in patients with UC and whether there is a role for vitamin D as a treatment for UC.

Growth and bone health in pediatric intestinal failure patients receiving long-term parenteral nutrition

BACKGROUND

Children with chronic intestinal failure (IF) treated with long-term parenteral nutrition (PN) may present with low bone mineral density (BMD). The cause may reflect small body size or suboptimal bone mineralization.

OBJECTIVE

We assessed growth and bone health in children with severe IF.

DESIGN

Height, weight, and fracture history were recorded. The lumbar spine bone mass was measured in 45 consecutive patients (24 male subjects) aged 5-17 y receiving PN for a median of 5 y. BMD and bone mineral apparent density (BMAD) [ie, adjusted-for-height SD scores (SDSs)] were calculated.

RESULTS

Diagnoses were short bowel syndrome in 12 patients (27%), intestinal enteropathy in 20 patients (44%), and motility disorder in 13 patients (29%). Mean (±SD) weight, height, and body mass index SDSs were -0.8 ± 1.3, -1.80 ± 1.5, and 0.4 ± 1.3, respectively. The height SDS was less than -2 in 23 children (50%). Patients with enteropathy or intestinal mucosal inflammation (associated with dysmotility or short bowel) were significantly shorter than patients without enteropathy (P = 0.007). The BMD SDS was -1.7 ± 1.6, and the BMAD SDS was -1.4 ± 1.5, independent of primary diagnosis or mucosal inflammation. Nineteen patients (42%) had low BMD (SDS less than -2.0), and 14 patients (31%) had low BMAD. In 25 patients studied at 1-2-y intervals, the BMD SDS fell significantly with time, whereas BMAD declined less, which suggested that a poor bone mineral accretion reflected poor growth. A total of 11 of 37 patients (24%) had nonpathologic fractures (P = 0.3 compared with the general population).

CONCLUSIONS

Approximately 50% of children were short, and one-third of children had low BMD and BMAD. Children with enteropathy or intestinal mucosal inflammation are at greatest risk of growth failure. Close nutritional monitoring and bespoke PN should maximize the potential for growth and bone mass.

Enrichment of vitamin D response elements in RA-associated loci supports a role for vitamin D in the pathogenesis of RA

The aim of this study was to explore the role of vitamin D in rheumatoid arthritis (RA) pathogenesis by investigating the enrichment of vitamin D response elements (VDREs) in confirmed RA susceptibility loci and testing variants associated with vitamin D levels for association with RA. Bioinformatically, VDRE genomic positions were overlaid with non-HLA (human leukocyte antigen)-confirmed RA susceptibility regions. The number of VDREs at RA loci was compared to a randomly selected set of genomic loci to calculate an average relative risk (RR). Single-nucleotide polymorphisms (SNPs) in the DHCR7/NADSYN1 (nicotinamide adenine dinucleotide synthase 1) and CYP2R1 loci, previously associated with circulating vitamin D levels, were tested in UK RA cases (n=3870) and controls (n=8430). Significant enrichment of VDREs was seen at RA loci (P=9.23 × 10(-8)) when regions were defined either by gene (RR 5.50) or position (RR 5.86). SNPs in the DHCR7/NADSYN1 locus showed evidence of positive association with RA, rs4944076 (P=0.008, odds ratio (OR) 1.14, 95% confidence interval (CI) 1.03-1.24). The significant enrichment of VDREs at RA-associated loci and the modest association of variants in loci-controlling levels of circulating vitamin D supports the hypothesis that vitamin D has a role in the development of RA.

Longitudinal assessment of bone mineral density in children and adolescents with inflammatory bowel disease

OBJECTIVES

Low bone mineral density (BMD) is recognized as a potential problem in children with inflammatory bowel disease (IBD). We aimed to describe the longitudinal development of BMD in a population of Swedish pediatric patients with IBD.

METHODS

A total of 144 patients with IBD (93 males; 83 with ulcerative colitis [UC], 45 with Crohn disease [CD]) were examined with dual-energy x-ray absorptiometry at baseline. At follow-up 2 years later, 126 of the initial 144 patients were reexamined. BMD values are expressed as z scores.

RESULTS

Children with UC and CD had significantly lower mean BMD z scores for the lumbar spine (LS) at baseline and after 2 years. The reduction in BMD was equally pronounced in patients with UC and CD, and neither group improved their z score during the follow-up period. Furthermore, significantly lower mean BMD z scores for the LS were found at baseline in boys (-1.1 SD, ±2.7 SD, P < 0.001), but not in girls (-0.0 SD, ±3.0 SD). This finding remained unchanged at follow-up. Subanalyses of the different age groups at baseline showed the lowest BMD values in the group of patients ages 17 to 19 years in boys (mean z score for the LS 1.59 SD, ±3.1 SD) and in girls (mean z score for the LS -3.40 SD, ±3.1 SD); however, at follow-up, these patients had improved their BMD significantly (mean change z score for the LS 1.00 SD, 95% CI 0.40-1.60; 1.90 SD, 95% CI 0.60-3.20).

CONCLUSIONS

In this longitudinal study, the entire group of pediatric patients with IBD showed permanent decreases in their BMD z scores for the LS; however, our data indicate that afflicted children have the potential to improve their BMD by the time they reach early adulthood.

Nutritional and probiotic supplementation in colitis models

In vitro and animals models have long been used to study human diseases and identify novel therapeutic approaches that can be applied to combat these conditions. Ulcerative colitis and Crohn's disease are the two main entities of inflammatory bowel disease (IBD). There is an intricate relationship between IBD features in human patients, in vitro and animal colitis models, mechanisms and possible therapeutic approaches in these models, and strategies that can be extrapolated and applied in humans. Malnutrition, particularly protein-energy malnutrition and vitamin and micronutrient deficiencies, as well as dysregulation of the intestinal microbiota, are common features of IBD. Based on these observations, dietary supplementation with essential nutrients known to be in short supply in the diet in IBD patients and with other molecules believed to provide beneficial anti-inflammatory effects, as well as with probiotic organisms that stimulate immune functions and resistance to infection has been tested in colitis models. Here we review current knowledge on nutritional and probiotic supplementation in in vitro and animal colitis models. While some of these strategies require further fine-tuning before they can be applied in human IBD patients, their intended purpose is to prevent, delay or treat disease symptoms in a non-pharmaceutical manner.

Micronutrient deficiencies in inflammatory bowel disease: from A to zinc

Inflammatory bowel disease (IBD) has classically been associated with malnutrition and weight loss, although this has become less common with advances in treatment and greater proportions of patients attaining clinical remission. However, micronutrient deficiencies are still relatively common, particularly in CD patients with active small bowel disease and/or multiple resections. This is an updated literature review of the prevalence of major micronutrient deficiencies in IBD patients, focusing on those associated with important extraintestinal complications, including anemia (iron, folate, vitamin B12) bone disease (calcium, vitamin D, and possibly vitamin K), hypercoagulability (folate, vitamins B6, and B12), wound healing (zinc, vitamins A and C), and colorectal cancer risk (folate and possibly vitamin D and calcium).

Hypovitaminosis D in adults with inflammatory bowel disease: potential role of ethnicity

BACKGROUND

Although vitamin D deficiency occurs in inflammatory bowel disease (IBD), it is currently unclear to what extent ethnicity affects vitamin D levels. Our aim was therefore to determine the ethnic variation in serum 25-hydroxyvitamin D status and its association with disease severity in adults with IBD.

METHODS

We conducted a prospective cohort study in ambulatory care IBD patients. Clinical disease severity was assessed through validated questionnaires. Serum 25-hydroxyvitamin D levels were used for vitamin D status. C-reactive protein (CRP), ferritin and hemoglobin (Hgb) levels were correlated with serum 25-hydroxyvitamin D levels.

RESULTS

Sixty ulcerative colitis (UC) and forty Crohn's disease (CD) patients were enrolled comprising 65 % Caucasians and 29 % South Asians. However, South Asians had consistently lower average serum 25-hydroxyvitamin D levels (All 44.8 ± 18.1 nmol/L, UC 48.2 ± 18.3 nmol/L, CD 24.3 ± 13.3 nmol/L). Hypovitaminosis D was found in 39 % of All, 36.7 % of UC and 42.5 % of CD patients. A significantly higher proportion of South Asians were vitamin D deficient when compared to Caucasians in All and CD groups (58.6 % vs. 30.8 %, p = 0.01 and 85.7 % vs. 32.3 %, p < 0.01, respectively).

CONCLUSIONS

A significantly higher percentage of South Asians had hypovitaminosis D when compared to Caucasians. Disease severity trended towards an inverse relationship with vitamin D status in all South Asian and Caucasian CD patients, although most patients in this study had only mild to moderate disease. We suggest that vitamin D supplementation should be considered in all adult IBD patients.

Nutritional management of adults with inflammatory bowel disease: practical lessons from the available evidence

Inflammatory bowel disease (IBD) is associated with impairment of nutritional status both anthropometrically and biochemically, which results from both qualitative and quantitative changes in dietary intake alongside disease activity. Dietary intervention to replace deficiency is essential and may also be used to treat active disease and to reduce symptoms. The evidence for dietary interventions in this area is reviewed and the following recommendations made: ■Assessment of nutritional status is an essential part of the investigation of all patients with IBD and deficiency should be actively sought.■Any patient with macro- or micronutrient deficiency should be referred for dietetic assessment.■Micronutrient deficiency (most frequently iron, vitamin B12, folate and magnesium) should be replaced aggressively, parenterally if necessary.■Significant improvement in gastrointestinal symptoms can be achieved by low-residue diets (for stricturing disease) and (always under dietetic supervision) management of lactose and other intolerances.■Irritable bowel syndrome symptoms in patients with IBD can respond to low fermentable oligo-, di-, monosaccharide and polyol (FODMAP) diets, again this must be done under dietetic supervision.■Active Crohn's disease can be treated by exclusive enteral nutrition (elemental/polymeric/altered fat formulations all have equivalent efficacy).■Enteral nutrition can maintain remission in Crohn's disease and in this context can be given alongside normal oral intake.■Nutritional support does not have an established role in the treatment of active ulcerative colitis, other than in the management of malnutrition.■Total parenteral nutrition should not be used unless intestinal failure occurs.■There is insufficient evidence to support the routine use of Ω3 fish oil, prebiotics and glutamine in the treatment of active IBD.

The impact of vitamin D deficiency on immune T cells in asthmatic children: a case-control study

Background

Vitamin D exerts profound effects on both adaptive and innate immune functions involved in the development and course of autoimmune and inflammatory diseases. As the incidence of vitamin D insufficiency is surprisingly high in the general population, experimental studies have started to investigate whether vitamin D levels (measured as serum 25 hydroxy vitamin D-25[OH]D) are correlated with immune cells and clinical parameters.

Purpose

The aim of the present research was to investigate serum vitamin D status in a case-control study in children with asthma and to study associations between vitamin D levels and certain immunological parameters.

Materials and methods

A case control study of thirty-nine children with clinically controlled asthma was enrolled to assess the relationship between serum vitamin D concentrations and disease activity. Vitamin D was assayed with a radioimmunoassay kit. We evaluated the relationship between vitamin D concentrations and forced vital capacity (FVC), forced expiratory volume in 1 second (FEV₁), and the FEV₁/FVC ratio. Correlations between inflammatory mediators, Th1, Th2, Th17, and regulatory T cells (Treg) and vitamin D were investigated.

Results

Only 15.38% of our asthmatic children had a sufficient serum 25(OH)D (≥30 ng/mL) whereas 80% of healthy children expressed sufficient levels. Deficient values of vitamin D (<20 ng/mL) were observed in 17 (43.59%) asthmatic patients (14.40 ± 3.30 ng/mL; P = 0.0001). Deficiency was not observed in controls. Th1/Th2 ratio was significantly correlated to 25(OH) D level (r = 0.698; P = 0.0001). A significant negative correlation was observed between serum interleukin-17 and vitamin D levels in young asthmatics (r = −0.617; P = 0.001). A significant correlation was observed between CD25⁺Foxp3⁺ Treg cells and vitamin D values in asthmatics (r = 0.368; P = 0.021).

Conclusion

Even in a southern Mediterranean country, hypovitaminosis D is frequent in children with asthma. Our findings suggest that vitamin D is an important promoter of T cell regulation in vivo in young asthmatics.

Management of inflammatory bowel disease with vitamin D: beyond bone health

A relationship between vitamin D and several disorders, including Crohn's disease (CD), has recently been proposed. Vitamin D appears to have several important actions beyond the maintenance of bone health, including various effects on the immune system. Vitamin D deficiency has been implicated in the development of CD, and its analogues may have a role in the treatment of CD. Current research also suggests a role for vitamin D in counteracting some IBD-specific complications, including osteopenia, colorectal neoplasia, and depression. There remains a need for prospective studies to further delineate these relationships. Given current evidence and the apparent safety of vitamin D supplementation, it appears reasonable to screen for and treat vitamin D deficiency in patients with IBD.

Vitamin D deficiency is associated with mortality in the medical intensive care unit

INTRODUCTION

The incidence of vitamin D deficiency in critically ill patients has been reported to range from as low as 17% to as high as 79%. Data regarding the relationship between 25-hydroxyvitamin D levels and outcomes in the medical intensive care unit are sparse. The goal of the study was to evaluate the prevalence of 25-hydroxyvitamin D deficiency in the medical intensive care unit and its relationship with outcomes.

METHOD

This was a retrospective study in a medical intensive care unit (MICU) at an inner city community hospital. The study period was between October 2009 and February 2010.

RESULTS

Of the 932 patients admitted during the study period, 25-hydroxyvitamin D vitamin D (25(OH)D) levels were available in 523 (53%); 86 of them were excluded from the study due to readmission to the intensive care unit. Deficiency was defined as 0 to 19.9 ng/dL 25(OH)D levels, insufficiency as 20 to 29.9 ng/dL, and normal levels as ≥30 ng/dL. Of the 437 patients studied, 25(OH)D deficiency was identified in 340 (77.8%), insufficiency in 74 (16.9%), and normal levels in 23 (5.3%) patients. Patients with 25(OH)D deficiency/insufficiency were younger (P = 0.015), were male (P = 0.001), and had kidney disease (P = 0.017) and lower total serum calcium levels (P = 0.003). Hospital mortality was higher in patients with 25(OH)D deficiency (P = 0.01). No differences in ventilator days or length of stay in the MICU were evident among the three groups. Analysis by multiple logistic regression demonstrated that acute physiology and chronic health evaluation (APACHE) IV score ((odds ratio (OR) 1.036; 95% confidence interval (CI) 1.024-1.048, P < 0.0001), ventilator requirement (OR 7.7; 95% CI 4.3-13.98, P < 0.0001), 25(OH) D levels(OR 0.942; 95% CI 0.942-0.904, P < 0.0005) and 25(OH) D deficiency (OR 8.7; 95% CI 1.03-72.8, P < 0.0469) showed statistical significance. There was no association between 25(OH)]D insufficiency and hospital mortality. The mean 25(OH)D level of survivors (27.9 ± 9.7 ng/dL) was higher than for non-survivors (9.7 ± 4.7 ng/dL; P < 0.0001).

CONCLUSIONS

The study results demonstrate an association between 25(OH)D deficiency and hospital mortality in MICU patients. A randomized prospective study to evaluate the effect of vitamin D replacement therapy on mortality is warranted.

Vitamin D deficiency in patients with inflammatory bowel disease: association with disease activity and quality of life

BACKGROUND

Vitamin D deficiency is common in inflammatory bowel disease (IBD). The aim of the study was to determine the prevalence and predictors of vitamin D deficiency in an IBD cohort. It was hypothesized that vitamin D deficiency is associated with increased disease activity and lower health-related quality of life (HRQOL).

METHODS

This was a retrospective cohort study. Harvey-Bradshaw index and ulcerative colitis disease activity index were used to assess disease activity. Short Inflammatory Bowel Disease Questionnaire scores were used to assess HRQOL. Multivariate logistic regression was used to identify independent predictors of vitamin D deficiency and its association with disease activity and HRQOL.

RESULTS

The study included 504 IBD patients (403 Crohn's disease [CD] and 101 ulcerative colitis [UC]) who had a mean disease duration of 15.5 years in CD patients and 10.9 years in UC patients; 49.8% were vitamin D deficient, with 10.9% having severe deficiency. Vitamin D deficiency was associated with older age (P = .004) and older age at diagnosis (P = .03). Vitamin D deficiency was associated with lower HRQOL (regression coefficient -2.21, 95% confidence interval [CI], -4.10 to -0.33) in CD but not UC (regression coefficient 0.41, 95% CI, -2.91 to 3.73). Vitamin D deficiency was also associated with increased disease activity in CD (regression coefficient 1.07, 95% CI, 0.43 to 1.71).

CONCLUSIONS

Vitamin D deficiency is common in IBD and is independently associated with lower HRQOL and greater disease activity in CD. There is a need for prospective studies to assess this correlation and examine the impact of vitamin D supplementation on disease course.

Use of a novel vitamin D bioavailability test demonstrates that vitamin D absorption is decreased in patients with quiescent Crohn's disease

BACKGROUND

Vitamin D deficiency is a common problem in patients with Crohn's disease (CD). The aim of this study was to determine the ability of normal subjects and patients with quiescent CD to absorb vitamin D(2) using a novel vitamin D bioavailability test. In addition, we evaluated whether the location of disease or previous surgery had any influence on the bioavailability of vitamin D(2) in CD patients.

METHODS

Ten normal subjects (50% female) and 37 CD patients with quiescent disease (51% female) were included in this study. Subjects who recently received any vitamin D(2) were excluded. The vitamin D bioavailability test was performed in all subjects. After a baseline blood draw, all subjects were then given a single 50,000 IU oral dose of vitamin D(2) in a capsule formulation and had their blood drawn 12 hours later to determine serum vitamin D(2), which reflected their vitamin D(2) absorption capacity.

RESULTS

Forty-two percent and 29% of CD patients were found to be either vitamin D-deficient (25-hydroxyvitamin D [25(OH)D] ≤20 ng/mL] or insufficient [25(OH)D 21-29 ng/mL], respectively. Twelve hours after ingesting 50,000 IU vitamin D(2) , vitamin D(2) levels rose from a baseline of 0.7 ± 0.7 ng/mL (mean ± SEM) to 49.8 ± 3.0 ng/mL in normal subjects. In CD patients, baseline vitamin D(2) levels rose from 0 ng/mL to 34.8 ± 2.8 ng/mL. CD patients had on average a 30% decrease in their ability to absorb vitamin D(2) (P = 0.01). Moreover, we found a wide variability of vitamin D(2) bioavailability in CD patients. Analysis of variance (ANOVA) revealed no statistical difference of vitamin D(2) bioavailability between patients in the CD subgroup stratified by the location of disease, the type of surgery, and receiving or not receiving surgery.

CONCLUSIONS

More than 70% of the patients with quiescent CD were vitamin D-deficient or insufficient. The ability to absorb vitamin D(2) in CD patients is unpredictable and the only way to determine this is to perform a vitamin D bioavailability test. Use of this test may guide clinicians in administering the appropriate therapeutic dose of vitamin D for treating vitamin D deficiency in patients with CD.

Vitamin D and immune function: an overview

Immunomodulatory actions of vitamin D have been recognised for over a quarter of a century, but it is only in the last few years that the significance of this to normal human physiology has become apparent. Two key factors have underpinned this revised perspective. Firstly, there are increasing data linking vitamin insufficiency with prevalent immune disorders. Improved awareness of low circulating levels of precursor 25-hydroxyvitamin D in populations across the globe has prompted epidemiological investigations of health problems associated with vitamin D insufficiency. Prominent among these are autoimmune diseases such as multiple sclerosis, type 1 diabetes and Crohn's disease, but more recent studies indicate that infections such as tuberculosis may also be linked to low 25-hydroxyvitamin D levels. The second factor expanding the link between vitamin D and the immune system is our improved knowledge of the mechanisms that facilitate this association. It is now clear that cells from the immune system contain all the machinery needed to convert 25-hydroxyvitamin D to active 1,25-dihydroxyvitamin D, and for subsequent responses to 1,25-dihydroxyvitamin D. Mechanisms such as this are important for promoting antimicrobial responses to pathogens in macrophages, and for regulating the maturation of antigen-presenting dendritic cells. The latter may be a key pathway by which vitamin D controls T-lymphocyte (T-cell) function. However, T-cells also exhibit direct responses to 1,25-dihydroxyvitamin D, notably the development of suppressor regulatory T-cells. Collectively these observations suggest that vitamin D is a key factor linking innate and adaptive immunity, and both of these functions may be compromised under conditions of vitamin D insufficiency.

Antibacterial effects of vitamin D

Interaction between vitamin D and the immune system has been recognized for many years, but its relevance to normal human physiology has only become evident in the past 5 years. Studies of innate immune responses to pathogens such as Mycobacterium tuberculosis have shown that pathogen-recognition receptor-mediated activation of localized vitamin D metabolism and signaling is a key event associated with infection. Vitamin D, acting in an intracrine fashion, is able to induce expression of antibacterial proteins and enhance the environment in which they function. The net effect of these actions is to support increased bacterial killing in a variety of cell types. The efficacy of such a response is highly dependent on vitamin D status; in other words, the availability of circulating 25-hydroxyvitamin D for intracrine conversion to active 1,25-dihydroxyvitamin D by the enzyme 25-hydroxyvitamin D-1α-hydroxylase. The potential importance of this mechanism as a determinant of human disease is underlined by increasing awareness of vitamin D insufficiency across the globe. This Review will explore the molecular and cellular systems associated with antibacterial responses to vitamin D in different tissues and possible consequences of such a response for the prevention and treatment of human immune disorders.

Risk of diagnosed fractures in children with inflammatory bowel diseases

BACKGROUND

Decreased bone mass is common in children with inflammatory bowel disease (IBD); however, fracture risk is unknown. We sought to evaluate fracture risk in children with IBD as compared to unaffected controls and determine whether this risk is affected by geographical region (a proxy for sun/vitamin D exposure) and oral steroid use.

METHODS

We identified cases of Crohn's disease (CD) and ulcerative colitis (UC), less than 20 years of age, using administrative data from 87 health plans. Each case was matched to three controls on the basis of age, gender, and geographical region. We identified fractures in cases and controls using ICD-9 diagnosis codes and measured oral steroid exposure using NDC codes.

RESULTS

The study included 733 children with CD, 488 with UC, and 3287 controls (mean age 15 years). IBD was not associated with a higher risk of fracture at any site (CD odds ratio [OR] 0.8, 95% confidence interval [CI] 0.6-1.1; UC OR 1.4, 95% CI 1.0-2.1) or at multiple sites (CD OR 0.8, 95% CI 0.4-1.7; UC OR 0.4, 95% CI 0.1-1.4). Among IBD patients we did not identify any significant differences in the fracture rate between those residing in the Northeast/Midwest versus the South (OR 1.3, 95% CI 0.8-2.2). Steroid exposure was not associated with the occurrence of fractures (P = 0.6).

CONCLUSIONS

Children with IBD are no more likely to have experienced a diagnosed fracture than age-, sex-, and gender-matched controls.

Vitamin D deficiency in children with inflammatory bowel disease

BACKGROUND

Osteopenia and osteoporosis are commonly seen in inflammatory bowel disease (IBD). Vitamin D deficiency potentially contributes to diminished bone acquisition in childhood.

OBJECTIVES

The objectives of this study were to assess vitamin D in a group of Australian children with IBD and to ascertain associations between vitamin D status and key clinical factors, for example disease location and severity.

METHODS

Data were obtained retrospectively from the records of children with IBD who had at least one measurement of serum 25-hydroxyvitamin D (25(OH)D) over a two-year period. Demographic variables, disease activity, inflammatory markers, disease location, duration, and therapy were recorded. Moderate and severe deficiency were defined as 25(OH)D <51 nmol/l and <30 nmol/l, respectively. Insufficiency was defined as 25(OH)D between 51 and 75 nmol/l.

RESULTS

Overall, the mean 25(OH)D level in 78 children (104 measurements) was 71.2 (SD ± 26.5) nmol/l. Fifteen (19%) children were vitamin D deficient and 30 (38%) children were insufficient. Levels of 25(OH)D were not associated with disease location or use of immunosuppressive drugs. Children with vitamin D deficiency had greater corticosteroid exposure than those with normal status (P = 0.001). The mean 25(OH)D of 38 children treated with nutritional therapy at diagnosis was higher than for 17 children initially treated with corticosteroids (P = 0.04).

CONCLUSIONS

A high proportion of these Australian children with IBD were vitamin D deficient. This emphasizes the importance of monitoring vitamin D status, and treating deficiency, in the management of pediatric IBD. The possible benefit of nutritional therapy in protection against vitamin D deficiency requires further prospective study.

Effect of vitamin D supplementation on muscle strength: a systematic review and meta-analysis

This systematic review demonstrates that vitamin D supplementation does not have a significant effect on muscle strength in vitamin D replete adults. However, a limited number of studies demonstrate an increase in proximal muscle strength in adults with vitamin D deficiency.

INTRODUCTION

The purpose of this study is to systematically review the evidence on the effect of vitamin D supplementation on muscle strength in adults.

METHODS

A comprehensive systematic database search was performed. Inclusion criteria included randomised controlled trials (RCTs) involving adult human participants. All forms and doses of vitamin D supplementation with or without calcium supplementation were included compared with placebo or standard care. Outcome measures included evaluation of strength. Outcomes were compared by calculating standardised mean difference (SMD) and 95% confidence intervals.

RESULTS

Of 52 identified studies, 17 RCTs involving 5,072 participants met the inclusion criteria. Meta-analysis showed no significant effect of vitamin D supplementation on grip strength (SMD -0.02, 95%CI -0.15,0.11) or proximal lower limb strength (SMD 0.1, 95%CI -0.01,0.22) in adults with 25(OH)D levels > 25 nmol/L. Pooled data from two studies in vitamin D deficient participants (25(OH)D <25 nmol/L) demonstrated a large effect of vitamin D supplementation on hip muscle strength (SMD 3.52, 95%CI 2.18, 4.85).

CONCLUSION

Based on studies included in this systematic review, vitamin D supplementation does not have a significant effect on muscle strength in adults with baseline 25(OH)D >25 nmol/L. However, a limited number of studies demonstrate an increase in proximal muscle strength in adults with vitamin D deficiency.

Nutrition in pediatric inflammatory bowel disease

Nutrition interventions play a central role in the treatment and management of inflammatory bowel disease in children. Malnutrition is a common presenting symptom in both pediatric ulcerative colitis and Crohn's disease and is associated with increased morbidity. Providing macronutrients can improve growth; likewise, identifying and correcting micronutrient deficiencies can improve comorbid conditions like osteopenia and anemia. Although many patients manipulate their diets to help treat their inflammatory bowel disease, only parenteral nutrition with bowel rest and exclusive enteral nutrition therapy have been shown effective for the treatment of inflammatory bowel disease.

Intrinsic requirement for the vitamin D receptor in the development of CD8αα-expressing T cells

Vitamin D and vitamin D receptor (VDR) deficiency results in severe symptoms of experimental inflammatory bowel disease in several different models. The intraepithelial lymphocytes of the small intestine contain large numbers of CD8αα(+) T cells that have been shown to suppress the immune response to Ags found there. In this study, we determined the role of the VDR in the development of CD8αα(+) T cells. There are fewer total numbers of TCRαβ(+) T cells in the gut of VDR knockout (KO) mice, and that reduction was largely in the CD8αα(+) TCRαβ(+) cells. Conversely TCRγδ(+) T cells were normal in the VDR KO mice. The thymic precursors of CD8αα(+) TCRαβ(+) cells (triple-positive for CD4, CD8αα, and CD8αβ) were reduced and less mature in VDR KO mice. In addition, VDR KO mice had a higher frequency of the CD8αα(+) TCRαβ(+) precursors (double-negative [DN] TCRαβ(+) T cells) in the gut. The proliferation rates of the DN TCRαβ(+) gut T cells were less in the VDR KO compared with those in wild type. Low proliferation of DN TCRαβ(+) T cells was a result of the very low expression of the IL-15R in this population of cells in the absence of the VDR. Bone marrow transplantation showed that the defect in VDR KO CD8αα(+) TCRαβ(+) cells was cell intrinsic. Decreased maturation and proliferation of CD8αα(+) TCRαβ(+) cells in VDR KO mice results in fewer functional CD8αα(+) TCRαβ(+) T cells, which likely explains the increased inflammation in the gastrointestinal tract of VDR KO and vitamin D-deficient mice.

Why do T cells express the vitamin D receptor?

Vitamin D is an important regulator of immune function. T cells express the vitamin D receptor (VDR) and have been shown to be direct and indirect vitamin D targets. Why should T cells be responsive to vitamin D? The data suggest that expression of the VDR is required for the development of two cell types, NKT cells and CD8αα T cells, which inhibit autoimmunity. In addition, effector T cell cytokine production is regulated by vitamin D. Available evidence suggests that NKT and CD8αα T cells express the VDR as part of the selection process to protect against the generation of autoimmunity, particularly in the gut.

Evaluation of vitamin D endocrine system (VDES) status and response to treatment of patients in intensive care units (ICUs) using an on-line SPE-LC-MS/MS method

Vitamin D deficiency is recognized as one of the most common chronic medical conditions in the world. Vitamin deficiency has been associated with increased mortality. The aim of the study here presented was to evaluate the vitamin D endocrine system (VDES) status in healthy blood donors and critically ill patients baseline and in response to treatment during a week with two doses of 1.5 mg of 25-hydroxyvitamin D3 and 2 microg calcitriol (1,25(OH)2D3) IV on alternate days, by monitoring levels in serum of major vitamin D metabolites in critically ill patients. Group 1: healthy blood donors (control group) (n=92), and group 2: critically ill subjects from an intensive care unit (ICU) (n=33). Critically ill patients were divided into three groups: group A (n=12) is the control group; group B (n=11), administration PO 1,5 mg of 25(OH)D3, in days 0 and 4 of treatment; and group C (n=11), administration IV of 2 microg 1,25(OH)2D3 on alternate days. Baseline serum levels of vitamin D2 and 25(OH)D2 were not detected. Vitamin D3 (9.8 vs 26.0 nM) (p<0.05), 25(OH)D3 (13.3 vs 52.3 nM) (p<0.001), and 1,25(OH)2D3 (53.8 vs 120.5 pM) (p<0.01) serum levels were significantly lower in critically ill subjects than in healthy donors. After treatment in group B: 25OHD3 increased to 46.0+/-16.5 ng/ml (p<0.0001) (22.2%<75 nM, 11.1% <50 nM). 1,25(OH)2D3 increased to 121.8+/-61.8 pM<0.01 whereas were slightly decreased in the other groups during the study. 24,25(OH)2D3 serum levels were increased in patients treated with calcitriol 8.5+/-5.3 vs 24.8+/-16.3 nM (p<0.05) while the levels kept stable in group A patients. In summary, critically ill patients have a severe vitamin D deficiency, which can be easily corrected by administration of high doses of 25OHD (PO). The VDES functional deficiency could be probably also corrected through administration of calcitriol (IV). Both treatments could produce an improvement in the general health and probably a reduction in overall mortality risk of the critically ill patients.

Inflammatory bowel diseases, celiac disease, and bone

The article summarizes the current knowledge on the pathogenesis, clinical aspects and treatment of bone problems in the major inflammatory bowel diseases (Crohn's disease and ulcerative colitis) and celiac disease. It presents the physiological relationship between intestine and bone as well as the alterations determined by disease-disrupted intestinal integrity. Two hypotheses about the pathogenetic mechanisms of bone metabolism derangements and bone loss are discussed: the classical one, that indicates calcium malabsorption as the main culprit, and the new one, that emphasizes the role of inflammation. The article summarizes the available epidemiological data about osteopenia/osteoporosis and fragility fractures in these chronic intestinal diseases and presents the state-of-the-art treatment options.

Vitamin D and the immune system: new perspectives on an old theme

Interaction with the immune system is one of the most well-established nonclassic effects of vitamin D. For many years this was considered to be a manifestation of granulomatous diseases such sarcoidosis, in which synthesis of active 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) is known to be dysregulated. However, recent reports have supported a role for 1,25(OH)(2)D(3) in mediating normal function of the innate and adaptive immune systems. Crucially, these effects seem to be mediated via localized autocrine or paracrine synthesis of 1,25(OH)(2)D(3) from precursor 25-hydroxyvitamin D(3), the main circulating metabolite of vitamin D. The ability of vitamin D to influence normal human immunity is highly dependent on the vitamin D status of individuals, and may lead to aberrant response to infection or autoimmunity in those who are lacking vitamin D. The potential health significance of this has been underlined by increasing awareness of impaired vitamin D status in populations across the globe. This article describes some of the recent developments with respect to vitamin D and the immune system, and possible clinical implications.

Nutritional considerations in pediatric inflammatory bowel disease

Nutrition is a critical part of the management of inflammatory bowel disease (IBD) in children and adults. Malnutrition and micronutrient deficiencies are common at the time of diagnosis and may persist throughout the course of the disease. There are a number of similarities with regards to the nutritional complications and the approach to nutritional management in IBD in both children and adults, but there are also important differences. Growth failure, pubertal delay and the need for corticosteroid-sparing regimens are of higher importance in pediatrics. In the pediatric population, exclusive enteral nutrition may be equivalent to corticosteroids in inducing remission in acute Crohn's disease, and may have benefits over corticosteroids in children. Adherence with exclusive enteral nutrition is better in children than in adults. Iron deficiency anemia is an important problem for adults and children with IBD. Intravenous iron administration may be superior to oral iron supplementation. Ensuring adequate bone health is another critical component of nutritional management in IBD, but guidelines for screening and therapeutic interventions for low bone mineral density are lacking in children.

Vitamin D deficiency in mice impairs colonic antibacterial activity and predisposes to colitis

Vitamin D insufficiency is a global health issue. Although classically associated with rickets, low vitamin D levels have also been linked to aberrant immune function and associated health problems such as inflammatory bowel disease (IBD). To test the hypothesis that impaired vitamin D status predisposes to IBD, 8-wk-old C57BL/6 mice were raised from weaning on vitamin D-deficient or vitamin D-sufficient diets and then treated with dextran sodium sulphate (DSS) to induce colitis. Vitamin D-deficient mice showed decreased serum levels of precursor 25-hydroxyvitamin D(3) (2.5 +/- 0.1 vs. 24.4 +/- 1.8 ng/ml) and active 1,25-dihydroxyvitamin D(3) (28.8 +/- 3.1 vs. 45.6 +/- 4.2 pg/ml), greater DSS-induced weight loss (9 vs. 5%), increased colitis (4.71 +/- 0.85 vs. 1.57 +/- 0.18), and splenomegaly relative to mice on vitamin D-sufficient chow. DNA array analysis of colon tissue (n = 4 mice) identified 27 genes consistently (P < 0.05) up-regulated or down-regulated more than 2-fold in vitamin D-deficient vs. vitamin D-sufficient mice, in the absence of DSS-induced colitis. This included angiogenin-4, an antimicrobial protein involved in host containment of enteric bacteria. Immunohistochemistry confirmed that colonic angiogenin-4 protein was significantly decreased in vitamin D-deficient mice even in the absence of colitis. Moreover, the same animals showed elevated levels (50-fold) of bacteria in colonic tissue. These data show for the first time that simple vitamin D deficiency predisposes mice to colitis via dysregulated colonic antimicrobial activity and impaired homeostasis of enteric bacteria. This may be a pivotal mechanism linking vitamin D status with IBD in humans.

Vitamin D deficiency in the intensive care unit: an invisible accomplice to morbidity and mortality?

The association between vitamin D deficiency and chronic illness is well-known. Vitamin D deficiency has been associated with increased mortality in the general population. Despite this knowledge, vitamin D insufficiency is seldom considered and rarely replaced adequately, if at all, in critically ill patients in intensive care. We present a hypothetic model demonstrating how vitamin D deficiency may be an unrecognized contributor to adverse outcome in intensive care patients.

Combination treatment with progesterone and vitamin D hormone may be more effective than monotherapy for nervous system injury and disease

More than two decades of pre-clinical research and two recent clinical trials have shown that progesterone (PROG) and its metabolites exert beneficial effects after traumatic brain injury (TBI) through a number of metabolic and physiological pathways that can reduce damage in many different tissues and organ systems. Emerging data on 1,25-dihydroxyvitamin D(3) (VDH), itself a steroid hormone, have begun to provide evidence that, like PROG, it too is neuroprotective, although some of its actions may involve different pathways. Both agents have high safety profiles, act on many different injury and pathological mechanisms, and are clinically relevant, easy to administer, and inexpensive. Furthermore, vitamin D deficiency is prevalent in a large segment of the population, especially the elderly and institutionalized, and can significantly affect recovery after CNS injury. The combination of PROG and VDH in pre-clinical and clinical studies is a novel and compelling approach to TBI treatment.

Inflammatory bowel disease causes reversible suppression of osteoblast and chondrocyte function in mice

Decreased bone density and stature can occur in pediatric patients with inflammatory bowel disease (IBD). Little is known about how IBD broadly impacts the skeleton. To evaluate the influence of an acute episode of IBD on growing bone, 4-wk-old mice were administered 5% dextran sodium sulfate (DSS) for 5 days to induce colitis and their recovery was monitored. During active disease and early recovery, trabecular bone mineral density, bone volume, and thickness were decreased. Cortical bone thickness, outer perimeter, and density were also decreased, whereas inner perimeter and marrow area were increased. These changes appear to maintain bone strength since measures of moments of inertia were similar between DSS-treated and control mice. Histological (static and dynamic), serum, and RNA analyses indicate that a decrease in osteoblast maturation and function account for changes in bone density. Unlike some conditions of bone loss, marrow adiposity did not increase. Similar to reports in humans, bone length decreased and correlated with decreases in growth plate thickness and chondrocyte marker expression. During disease recovery, mice experienced a growth spurt that led to their achieving final body weights and bone length, density, and gene expression similar to healthy controls. Increased TNF-alpha and decreased IGF-I serum levels were observed with active disease and returned to normal with recovery. Changes in serum TNF-alpha (increased) and IGF-I (decreased) paralleled changes in bone parameters and returned to normal values with recovery, suggesting a potential role in the skeletal response.

Recent advances in the renal-skeletal-gut axis that controls phosphate homeostasis

Under physiological conditions, homeostasis of inorganic phosphate (Pi) is tightly controlled by a network of increasingly more complex interactions and direct or indirect feedback loops among classical players, such as vitamin D (1,25(OH)2D3), parathyroid hormone (PTH), intestinal and renal phosphate transporters, and the recently described phosphatonins and minhibins. A series of checks and balances offsets the effects of 1,25(OH)2D3 and PTH to enable fine-tuning of intestinal and renal Pi absorptive capacity and bone resorption and mineralization. The latter include PHEX, FGF-23, MEPE, DMP1, and secreted FRP4. Despite this large number of regulatory components with complex interactions, the system has limited redundancy and is prone to dysregulation under pathophysiological conditions. This article reviews and synthesizes recent advances to present a new model of Pi homeostasis.

Nutritional concerns in pediatric inflammatory bowel disease patients

In approximately one-fourth of patients with Crohn's disease (CD) and ulcerative colitis (UC), disease onset occurs during childhood and adolescence. In addition to gastrointestinal and extraintestinal symptoms of inflammatory bowel disease (IBD), children with these conditions often experience one or more nutritional complications of their disease including growth failure, delayed puberty, osteoporosis, anemia, and micronutrient deficiencies. This article provides an overview of the epidemiology, pathophysiology, evaluation, and management of selected nutritional complications in pediatric IBD.

Vitamin D and human health: lessons from vitamin D receptor null mice

The vitamin D endocrine system is essential for calcium and bone homeostasis. The precise mode of action and the full spectrum of activities of the vitamin D hormone, 1,25-dihydroxyvitamin D [1,25-(OH)(2)D], can now be better evaluated by critical analysis of mice with engineered deletion of the vitamin D receptor (VDR). Absence of a functional VDR or the key activating enzyme, 25-OHD-1alpha-hydroxylase (CYP27B1), in mice creates a bone and growth plate phenotype that mimics humans with the same congenital disease or severe vitamin D deficiency. The intestine is the key target for the VDR because high calcium intake, or selective VDR rescue in the intestine, restores a normal bone and growth plate phenotype. The VDR is nearly ubiquitously expressed, and almost all cells respond to 1,25-(OH)(2)D exposure; about 3% of the mouse or human genome is regulated, directly and/or indirectly, by the vitamin D endocrine system, suggesting a more widespread function. VDR-deficient mice, but not vitamin D- or 1alpha-hydroxylase-deficient mice, and man develop total alopecia, indicating that the function of the VDR and its ligand is not fully overlapping. The immune system of VDR- or vitamin D-deficient mice is grossly normal but shows increased sensitivity to autoimmune diseases such as inflammatory bowel disease or type 1 diabetes after exposure to predisposing factors. VDR-deficient mice do not have a spontaneous increase in cancer but are more prone to oncogene- or chemocarcinogen-induced tumors. They also develop high renin hypertension, cardiac hypertrophy, and increased thrombogenicity. Vitamin D deficiency in humans is associated with increased prevalence of diseases, as predicted by the VDR null phenotype. Prospective vitamin D supplementation studies with multiple noncalcemic endpoints are needed to define the benefits of an optimal vitamin D status.

Altered endocrine and autocrine metabolism of vitamin D in a mouse model of gastrointestinal inflammation

The active form of vitamin D, 1,25-dihydroxyvitamin D3, [1,25(OH)2D3] has potent actions on innate and adaptive immunity. Although endocrine synthesis of 1,25(OH)2D3 takes place in the kidney, the enzyme that catalyzes this, 25-hydroxyvitamin D-1alpha-hydroxylase (CYP27b1 in humans, Cyp27b1 in mice), is expressed at many extra-renal sites including the colon. We have shown previously that colonic expression of CYP27b1 may act to protect against the onset of colitis. To investigate this further, we firstly characterized changes in Cyp27b1 expression in a mouse model of colitis. Mice treated with dextran sodium sulfate (DSS) showed weight loss, histological evidence of colitis, and increased expression of inflammatory cytokines. This was associated with decreased renal expression of Cyp27b1 (5-fold, P=0.013) and lower serum 1,25(OH)2D3 (51.8+/-5.9 pg/nl vs. 65.1+/-1.6 in controls, P<0.001). However, expression of CYP27b1 was increased in the proximal colon of DSS mice (4-fold compared with controls, P<0.001). Further studies were carried out using Cyp27b1 null (-/-) mice. Compared with+/-controls the Cyp27b1-/-mice showed increased weight loss (4.9% vs. 22.8%, P<0.001) and colitis. This was associated with raised IL-1 in the distal colon and IL-17 in the proximal and distal colon. Conversely, DSS-treated Cyp27b1-/-mice exhibited lower IL-10 in the proximal colon and toll-like receptors 2 and 4 in the distal colon. These data indicate that both local and endocrine synthesis of 1,25(OH)2D3 affect colitis in DSS-treated mice. Lack of Cyp27b1 exacerbates disease in this model, suggesting that similar effects may occur with vitamin D deficiency.

A network biology model of micronutrient related health

Micronutrients are involved in specific biochemical pathways and have dedicated functions in the body, but they are also interconnected in complex metabolic networks, such as oxidative-reductive and inflammatory pathways and hormonal regulation, in which the overarching function is to optimise health. Post-genomic technologies, in particular metabolomics and proteomics, both of which are appropriate for plasma samples, provide a new opportunity to study the metabolic effects of micronutrients in relation to optimal health. The study of micronutrient-related health status requires a combination of data on markers of dietary exposure, markers of target function and biological response, health status metabolites, and disease parameters. When these nutrient-centred and physiology/health-centred parameters are combined and studied using a systems biology approach with bioinformatics and multivariate statistical tools, it should be possible to generate a micronutrient phenotype database. From this we can explore external factors that define the phenotype, such as lifestage and lifestyle, and the impact of genotype, and the results can also be used to define micronutrient requirements and provide dietary advice. New mechanistic insights have already been developed using biological network models, for example genes and protein-protein interactions in the aetiology of type 2 diabetes mellitus. It is hoped that the challenge of applying this approach to micronutrients will, in time, result in a change from micronutrient oriented to a health oriented views and provide a more holistic understanding of the role played by multiple micronutrients in the maintenance of homeostasis and prevention of chronic disease, for example through their involvement in oxidation and inflammation.

Control of autoimmune diseases by the vitamin D endocrine system

1,25-Dihydroxyvitamin D(3) [1,25(OH)(2)D(3)], the biologically active form of vitamin D(3), is a secosteroid hormone essential for bone and mineral homeostasis. It regulates the growth and differentiation of multiple cell types, and displays immunoregulatory and anti-inflammatory properties. Cells involved in innate and adaptive immune responses--including macrophages, dendritic cells, T cells and B cells--express the vitamin D receptor (VDR), and can both produce and respond to 1,25(OH)(2)D(3). The net effect of the vitamin D system on the immune response is an enhancement of innate immunity coupled with multifaceted regulation of adaptive immunity. Epidemiological evidence indicates a significant association between vitamin D deficiency and an increased incidence of several autoimmune diseases, and clarification of the physiological role of endogenous VDR agonists in the regulation of autoimmune responses will guide the development of pharmacological VDR agonists for use in the clinic. The antiproliferative, prodifferentiative, antibacterial, immunomodulatory and anti-inflammatory properties of synthetic VDR agonists could be exploited to treat a variety of autoimmune diseases, from rheumatoid arthritis to systemic lupus erythematosus, and possibly also multiple sclerosis, type 1 diabetes, inflammatory bowel diseases, and autoimmune prostatitis.

Vitamin D deficiency in children and adolescents: epidemiology, impact and treatment

Vitamin D deficiency is highly prevalent among children and adolescents worldwide. The high rates of vitamin D deficiency during childhood are of major public health relevance, given the growing evidence that vitamin D deficiency may play a key role in the pathophysiology of many chronic diseases beyond rickets, including autoimmune conditions, cardiovascular diseases, and cancer. Identification, treatment, and prevention of vitamin D deficiency in childhood may therefore have profound health effects throughout the life span. In this review, we discuss the definitions, epidemiology, clinical implications, and treatment of vitamin D deficiency in children and adolescents.