Vitamin D intake and status in Ireland: a narrative review.

Vitamin D is crucial for musculoskeletal health, with evidence suggesting non-skeletal benefits. Cutaneous vitamin D synthesis is limited in Ireland due to its northern latitude (52-55°N) and the population is dependent on dietary sources, yet intakes are inadequate. No study to-date has comprehensively examined vitamin D intakes and status in Ireland (Northern Ireland and the Republic). We aimed to review the evidence since 2010 and summarise the results in subgroups of the Irish population. We found that in the largest studies prevalence of deficiency [25-hydroxyvitamin D (25(OH)D) < 30 nm/l] was 15-17% in pregnancy, 15-23% in children and 13% in adults. Approximately half the population had 25(OH)D < 50 nm/l. There were only four small studies in an ethnic population with the largest in Southeast Asians finding that 67% were deficient. All studies found higher rates of deficiency and levels <50 nm/l in winter v. summer. Vitamin D intake was lowest in children (mean 2⋅3-4⋅2 µg/d) and pregnant women (mean 1⋅9-5⋅1 µg/d) and highest in older adults (6⋅9 µg/d), with over 90% of the population not meeting the recommended daily allowance. This review indicates that low vitamin D status and dietary vitamin D intake are widespread with children, adolescents, younger adults, pregnant women and ethnic minorities most at-risk. However, data are sparse in at-risk groups including the Travelling community, non-Europeans and institutionalised adults. Given the significant prevalence of deficiency, public health policies to promote better awareness of recommended vitamin D intakes and explore the options of food fortification are needed to address this issue.

Low socioeconomic status predicts vitamin D status in a cross-section of Irish children.

Vitamin D is essential for bone and muscle health with adequate status in childhood crucial for normal skeletal development. We aimed to investigate vitamin D status in a convenience sample (n = 1226) of Irish children (aged 1-17 years) who had serum 25-hydroxyvitamin D (25(OH)D) tested by request of their GP at a Dublin Hospital between 2014 and 2020. We examined predictors including age, sex, season and socioeconomic status (SES). Vitamin D deficiency (<30 nmol/l) was prevalent affecting 23 % and was more common in disadvantaged areas (34 %) and in those aged >12 v. ≤12 years (24 % v. 16 %, P = 0⋅033). The greatest predictor was SES (disadvantaged v. affluent, OR 2⋅18, CI 1⋅34, 3⋅53, P = 0⋅002), followed by female sex (OR 1⋅57, CI 1⋅15, 2⋅14, P = 0⋅005) and winter season (October to February, OR 1⋅40, CI 1⋅07, 1⋅84, P = 0⋅015). A quarter of our sample of children were deficient, rising to one-third in those in disadvantaged areas. Females and those aged over 12 years had a higher prevalence of deficiency. Public health strategies to improve vitamin D status in Irish children, including systematic food fortification may need to be considered to address this issue.

Title: Understanding a Low Vitamin D State in the Context of COVID-19.

While a low vitamin D state has been associated with an increased risk of infection by SARS-CoV-2 in addition to an increased severity of COVID-19 disease, a causal role is not yet established. Here, we review the evidence relating to i) vitamin D and its role in SARS-CoV-2 infection and COVID-19 disease ii) the vitamin D status in the Irish adult population iii) the use of supplemental vitamin D to treat a deficient status and iv) the application of the Bradford-Hill causation criteria. We conclude that reverse causality probably makes a minimal contribution to the presence of low vitamin D states in the setting of COVID-19. Applying the Bradford-Hill criteria, however, the collective literature supports a causal association between low vitamin D status, SARS-CoV-2 infection, and severe COVID-19 (respiratory failure, requirement for ventilation and mortality). A biologically plausible rationale exists for these findings, given vitamin D's role in immune regulation. The thresholds which define low, deficient, and replete vitamin D states vary according to the disease studied, underscoring the complexities for determining the goals for supplementation. All are currently unknown in the setting of COVID-19. The design of vitamin D randomised controlled trials is notoriously problematic and these trials commonly fail for a number of behavioural and methodological reasons. In Ireland, as in most other countries, low vitamin D status is common in older adults, adults in institutions, and with obesity, dark skin, low UVB exposure, diabetes and low socio-economic status. Physiological vitamin D levels for optimal immune function are considerably higher than those that can be achieved from food and sunlight exposure alone in Ireland. A window exists in which a significant number of adults could benefit from vitamin D supplementation, not least because of recent data demonstrating an association between vitamin D status and COVID-19. During the COVID pandemic, we believe that supplementation with 20-25ug (800-1000 IU)/day or more may be required for adults with apparently normal immune systems to improve immunity against SARS-CoV-2. We expect that higher monitored doses of 37.5-50 ug (1,500-2,000)/day may be needed for vulnerable groups (e.g., those with obesity, darker skin, diabetes mellitus and older adults). Such doses are within the safe daily intakes cited by international advisory agencies.

Vitamin D and Hospital Admission in Older Adults: A Prospective Association.

The health effects of vitamin D are well documented, with increasing evidence of its roles beyond bone. There is, however, little evidence of the effects of vitamin D on hospitalisation among older adults. This study aimed to prospectively determine the relationship of vitamin D status in older adults with hospital admission and emergency department (ED) attendance. Trinity University of Ulster Department of Agriculture (TUDA) is a large cross-sectional study of older adults with a community population from three disease-defined cohorts (cognitive dysfunction, hypertension, and osteoporosis). Participants included in this analysis were recruited between 2008 and 2012. ED and hospital admission data were gathered from the date of TUDA participation until June 2013, with a mean follow up of 3.6 years. Of the 3093 participants, 1577 (50.9%) attended the ED during the period of follow-up. Attendees had lower mean serum 25(OH)D concentrations than non-attendees (59.1 vs. 70.6 nmol/L). Fully adjusted models showed an inverse association between vitamin D and ED attendance (Hazard Ratio (HR) 0.996; 95% Confidence Interval (CI) 0.995-0.998; p < 0.001). A total of 1269 participants (41%) were admitted to hospital during the follow-up. Those admitted had lower mean vitamin D concentrations (58.4 vs. 69.3 nmol/L, p < 0.001). In fully adjusted models, higher vitamin D was inversely associated with hospital admission (HR 0.996; 95% CI 0.994-0.998; p < 0.001) and length of stay (LOS) (ß = -0.95, p = 0.006). This study showed independent prospective associations between vitamin D deficiency and increased hospitalisation by older adults. The need for further evaluation of current recommendations in relation to vitamin D supplementation, with consideration beyond bone health, is warranted and should focus on randomised controlled trials.

Geomapping Vitamin D Status in a Large City and Surrounding Population-Exploring the Impact of Location and Demographics.

Vitamin D status was assessed in a large urban area to compare differences in deficiency and to geomap the results. In total, 36,466 participants from 28 geographical areas were identified in this cross-sectional, retrospective analysis of general practitioner (GP)-requested 25(OH)D tests at St James's Hospital, Dublin between 2014 and 2018. The population were community-dwelling adults, median age 50.7 (18-109 years) with 15% of participants deficient (<30 nmol/L), rising to 23% in the winter. Deficiency was greatest in younger (18-39 years) and oldest (80+ years) adults, and in males versus females (18% vs. 11%, p < 0.001). Season was the biggest predictor of deficiency (OR 4.44, winter versus summer, p < 0.001), followed by location (west Dublin OR 2.17, north Dublin 1.54, south Dublin 1.42 versus rest of Ireland, p < 0.001) where several urban areas with an increased prevalence of deficiency were identified. There was no improvement in 25(OH)D over the 5-year period despite increased levels of testing. One in four adults were vitamin D deficient in the winter, with significant variations across locations and demographics. Overall this study identifies key groups at risk of 25(OH)D deficiency and insufficiency, thus providing important public health information for the targeting of interventions to optimise 25(OH)D. Mandatory fortification may be necessary to address this widespread inadequacy.

Quantitative examination of the bone health status of older adults with intellectual and developmental disability in Ireland: a cross-sectional nationwide study.

OBJECTIVES: (1) To investigate the prevalence of osteopenia and osteoporosis among adults with intellectual disabilities (IDs) and (2) to examine alternative optimal bone screening techniques. DESIGN: Observational cross-sectional study. SETTING: Wave 2 (2013-2106) of the Intellectual Disability Supplement to the Irish Longitudinal Study on Ageing. PARTICIPANTS: A national representative sample of 604 male and female persons with ID aged 43 years and over. In total, 575 participants completed quantitative ultrasound (QUS) measurements for one or both feet. OUTCOME MEASURES: Participants underwent health assessments consisting of eight objective health measures including the standardised QUS of the calcaneus bone using a GE Lunar Achilles. A preinterview questionnaire and face-to-face interview were also completed. RESULTS: Objectively QUS identified poorer rates of bone health in people with ID overall with 74% indicating evidence of osteopenia (33.2%) or osteoporosis (41%). Females scored lower than males in the QUS t-scores -2.208 (±1.77) versus -1.78(±1.734). Bone status was stratified by gender (p=0.114), age (p=0.003), level of ID (p<0.0001) and living circumstance (p<0.0001). CONCLUSIONS: This study has shown the prevalence of poor bone health in people with ID is substantial implying an increased risk of fracture due to reduced skeletal integrity. QUS screening has been shown to be useful when combined with clinical risk factors.

Seasonal variation of serum vitamin D and the effect of vitamin D supplementation in Irish community-dwelling older people.

BACKGROUND: Ireland is at 53°N, and its population risk of vitamin D deficiency is high. Previous Irish studies suggested a significant seasonality of serum 25-hydroxyvitamin D [25(OH)D] and a beneficial effect of supplementation in raising 25(OH)D levels. However, in Irish older people, little is known about the magnitude of the supplementation effect and whether supplementation affects 25(OH)D seasonality. DESIGN: cross-sectional observational. SETTING: outpatient clinic. SUBJECTS: five hundred and forty-six community-dwelling subjects (mean age 73.0, SD 7.4; 68.5% females) were assessed between September 2007 and May 2009. METHODS: for supplemented and non-supplemented: 'cosinor' analysis (Pulse_XP®) of monthly 25(OH)D. Period global solar radiation (GSR) and solar elevation angle (SEA) data were collected as proxy markers of ultraviolet-B radiation exposure. Multivariate linear regression was conducted to investigate the independent effect of GSR and SEA on 25(OH)D, controlling for confounders. RESULTS: supplemented group (N = 183): 89.1% were on cholecalciferol 800 IU/day. Mean 25(OH)D = 64.1 (95% confidence interval: 52.2-75.8) nmol/l, with no significant seasonality; regression: neither GSR nor SEA predicted 25(OH)D. Non-supplemented group (N = 363): mean 25(OH)D = 40.3 (35.5-45.0) nmol/l, with significant seasonality (55.5% variance remaining), peak in August, amplitude = 6.0 (3.1-8.8) nmol/l; regression: both GSR (P = 0.002) and the interaction GSR * SEA (P = 0.018) predicted 25(OH)D. CONCLUSIONS: vitamin D supplementation was associated with a mean serum 25(OH)D increase of 23.8 nmol/l. Interestingly, supplementation seemed to blunt seasonality. In the supplemented group, 72.1% had individual 25(OH)D levels below the recommended 75 nmol/l. There is a case for universal supplementation in Irish older people, probably at a higher dose. Further research is needed to establish the optimum dose.