The role of sunlight exposure in determining the vitamin D status of the UK white Caucasian adult population
Vitamin D is necessary for bone health and is potentially protective against a range of malignancies. Opinions are divided on whether the proposed optimal circulating 25-hydroxyvitamin D [25(OH)D] level (≥ 32 ng mL⁻¹) is an appropriate and feasible target at population level. We examined whether personal sunlight exposure levels can provide vitamin D sufficient (≥ 20 ng mL⁻¹) and optimal status in the U.K. public. This prospective cohort study measured circulating 25(OH)D monthly for 12 months in 125 white adults aged 20-60 years in Greater Manchester. Dietary vitamin D and personal ultraviolet radiation (UVR) exposure were assessed over 1-2 weeks in each season. The primary analysis determined the post-summer peak 25(OH)D required to maintain sufficiency in wintertime. Dietary vitamin D remained low in all seasons (median 3·27 μg daily, range 2·76-4·15) while personal UVR exposure levels were high in spring and summer, low in autumn and negligible in winter. Mean 25(OH)D levels were highest in September [28·4 ng mL⁻¹; 28% optimal, zero deficient (<5 ng mL⁻¹)], and lowest in February (18·3 ng mL⁻¹; 7% optimal, 5% deficient). A February 25(OH)D level of 20 ng mL⁻¹ was achieved following a mean (95% confidence interval) late summer level of 30·4 (25·6-35·2) and 34·9 (27·9-41·9) ng mL⁻¹ in women and men, respectively, with 62% of variance explained by gender and September levels. Late summer 25(OH)D levels approximating the optimal range are required to retain sufficiency throughout the U.K. winter. Currently the majority of the population fails to reach this post-summer level and becomes vitamin D insufficient during the winter.
[Show abstract] [Hide abstract] ABSTRACT: Purpose: There are limited data on the contribution of fortified foods and nutritional supplements to intakes of vitamin D in young children. Our objective was to examine the intake, adequacy, risk of excessive intake and sources of dietary vitamin D. Methods: The nationally representative cross-sectional dietary survey of young children (aged 1-4 years) (n 500) was used to evaluate vitamin D intake and quantify the contribution of the base diet, fortified foods and nutritional supplements to total intake. Results: Median (IQR) intakes of vitamin D were generally low in this young population, ranging from 2.0 (1.9) to 2.5 (4.9) µg/day. Ninety-three and 78 % of children had intakes below 10 and 5 µg/day, respectively. While vitamin D supplement users (17 %) had the highest intakes [6.7 (6.4) µg/day] (P < 0.001), 74 % had intakes below 10 µg/day. Vitamin D-fortified foods, consumed by 77 % of children [2.2 (2.0) µg/day], made nutritionally significant contributions to intake [0.8 (1.6) µg/day], particularly in younger children [1.5 (4.6) µg/day]. Children who did not use nutritional supplements or fortified foods had significantly (P < 0.001) lower intakes of vitamin D than the other groups [1.0 (0.8) µg/day]. Our analyses show the importance of milk and yoghurt, meat and fortified ready-to-eat cereals as sources of vitamin D in this age group. The use of nutritional supplements or fortified foods at current levels does not represent a risk of intakes exceeding the European Food Safety Authority (EFSA) tolerable upper intake level (UL) (50 µg/day), as intakes did not exceed or even approach the UL (P95: 22 % of UL). Conclusion: Intakes of vitamin D in preschool children in Ireland are generally low. Nutritional supplements and fortified foods make significant contributions to intakes of vitamin D, without risk of unacceptably high intakes. Though supplements are effective in raising intakes of vitamin D in users, uptake is low (17 %). Food fortification may represent a suitable public health approach to increasing vitamin D intakes. The national food consumption data of Irish preschool children provide the ideal starting point for modelling of fortification scenarios to identify which foods and levels of addition will ensure effective and safe increases in vitamin D intake.0Comments 0Citations
- "Our analyses show the importance of milk and yoghurt, meat and fortified readyto-eat cereals as sources of vitamin D in this age group. The use of nutritional supplements or fortified foods at current to maintain healthy vitamin D status . Vitamin D is not ubiquitous in the food supply, found naturally in few foods, and typically in low concentrations. "
[Show abstract] [Hide abstract] ABSTRACT: In this study, we discuss the short- and the long-term variability of spectral UV irradiance at Thessaloniki, Greece, using a long, quality-controlled data set from two Brewer spectrophotometers. Long-term changes in spectral UV irradiance at 307.5, 324 and 350 nm for the period 1994–2014 are presented for different solar zenith angles and discussed in association with changes in total ozone column (TOC), aerosol optical depth (AOD) and cloudiness observed in the same period. Positive changes in annual mean anomalies of UV irradiance, ranging from 2 to 6 % per decade, have been detected both for clear- and all-sky conditions. The changes are generally greater for larger solar zenith angles and for shorter wavelengths. For clear-skies, these changes are, in most cases, statistically significant at the 95 % confidence limit. Decreases in the aerosol load and weakening of the attenuation by clouds lead to increases in UV irradiance in the summer, of 7–9 % per decade for 64° solar zenith angle. The increasing TOC in winter counteracts the effect of decreasing AOD for this particular season, leading to small, statistically insignificant, negative long-term changes in irradiance at 307.5 nm. Annual mean UV irradiance levels are increasing from 1994 to 2006 and remain relatively stable thereafter, possibly due to the combined changes in the amount and optical properties of aerosols. However, no statistically significant corresponding turning point has been detected in the long-term changes of AOD. The absence of signatures of changes in AOD in the short-term variability of irradiance in the UV-A may have been caused by changes in the single scattering albedo of aerosols, which may counteract the effects of changes in AOD on irradiance. The anti-correlation between the year-to-year variability of the irradiance at 307.5 nm and TOC is clear and becomes clearer as the AOD decreases.0Comments 1Citation
- "Thus, good quality measurements of the spectral UV irradiance and the main factors controlling its levels at the Earth's surface are of great importance for achieving better understanding and more accurate modelling of the interactions among UV radiation, ozone, aerosols, clouds and surface reflectivity (García et al., 2015; Kreuter et al., 2014; Mayer and Kylling, 2005; Schwander et al., 1997). Accurate knowledge of the levels of spectral surface UV irradiance is necessary in order to quantify effects on the health of humans (Kazantzidis et al., 2015; Webb et al., 2010) and ecosystems (Ballare et al., 2011; Häder et al., 2011), and prevent potential impacts from over-or under-exposure to UV radiation (Lucas et al., 2015 ). Additionally, reliable estimations of the trends of spectral surface UV irradiance provide useful information for assessing these impacts and for adopting proper measures (Morgenstern et al., 2008; Newman and McKenzie, 2011; van Dijk et al., 2013 ). "
[Show abstract] [Hide abstract] ABSTRACT: Data on vitamin D status among non-elderly adults from Central Europe are insufficient. Natural sunlight allows for cutaneous vitamin D synthesis only from April through August at latitudes over 54° in the northern hemisphere. In this study we aimed at determining vitamin D status among adults in the first weeks of autumn in northern Poland. A convenience sample of community-dwelling, predominantly urban and non-elderly adults was recruited in an outpatient clinic. Questionnaire and laboratory examinations were performed from September 26 through November 8. The latter comprised serum alkaline phosphatase activity (ALP), 25-hydroxyvitamin D (25(OH)D), parathyroid hormone (PTH), calcium, and phosphorus concentrations. 180 women and 124 men were enrolled into the study, aged 46+/-14.1 years (mean+/-standard deviation, SD). Mean 25-hydroxyvitamin D concentration of the studied sample was 21.1+/-9.3 ng/ml. More than 50% of studied subjects were vitamin D deficient (i.e. had 25(OH)D concentrations of less than 20 ng/ml), only 15.1% reached vitamin D concentrations of ≥30 ng/ml (sufficiency). Median 25(OH)D concentrations were higher in participants who declared longer sun exposure as well as those who supplemented vitamin D. A negative correlation was found between PTH and 25(OH)D concentrations: r=-0.23, p<0.001 (Spearman rank order test). While there are a number of methodological limitations concerning the current study, the acquired results broaden the scarce amount of data on vitamin D status in Central Europe. Our data correspond well with those from previous studies. The presented study should be considered precursory to further research.0Comments 0Citations
- "In a study by Webb and co-workers. 25(OH)D concentrations were determined repeatedly in adult participants in Greater Manchester (51° N) each month for a year . A minimum 32 ng/ml concentration has been put forward as a summer nadir value that decreased to non-deficient 25(OH)D concentrations during autumn and winter. "