Publications by authors named "Kirsten G Dowling"

Nickel (Ni) is a trace heavy metal of importance in biological and environmental systems, with well documented allergy and carcinogenic effects in humans. With Ni(II) as the dominant oxidation state, the elucidation of the coordination mechanisms and labile complex species responsible for its transportation, toxicity, allergy, and bioavailability is key to understanding its biological effects and location in living systems. Histidine (His) is an essential amino acid that contributes to protein structure and activity and in the coordination of Cu(II) and Ni(II) ions.

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The aim of this study was to determine if increased mortality associated with low levels of serum 25-hydroxyvitamin D (25(OH)D) reflects a causal relationship by using a Mendelian randomisation (MR) approach with genetic variants in the vitamin D synthesis pathway. Individual participant data from three European cohorts were harmonized with standardization of 25(OH)D according to the Vitamin D Standardization Program. Most relevant single nucleotide polymorphisms of the genes (rs12794714, rs10741657) and (rs12785878, rs11234027), were combined in two allelic scores.

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Ultraviolet-irradiated yeast (Saccharomyces cerevisiae) can be used to biofortify bakery products with vitamin D, but in bread, it was not effective in increasing serum 25-hydroxyvitamin D [25(OH)D] in humans, possibly because of the low digestibility of the yeast matrix. We investigated the effects of vitamin D-rich intact yeast cells and their separated fraction, yeast cell walls, which we hypothesized to provide vitamin D in a more bioavailable form, on serum 25(OH)D and its metabolites in growing female Sprague-Dawley rats (n = 54) compared to vitamin D and D supplements (8 treatment groups: 300 or 600 IU vitamin D/d, and a control group, 8-week intervention). The D supplement groups had the highest 25(OH)D concentrations, and the vitamin D supplement at the 600-IU dose increased 25(OH)D better than any yeast form (P < .

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Context: Current vitamin D recommendations have been established based on an assumption that there are no differences between Caucasian and other ethnic/racial groups in terms of vitamin D requirements. This assumption, largely made due to the absence of data, is a key knowledge gap identified by a number of authorities.

Objective: To test whether the distribution of dietary requirements for maintaining winter serum 25-hydroxyvitamin D [25(OH)D] concentrations ≥ 30 nmol/L (a priority threshold linked to vitamin D deficiency prevention) differ between Caucasian and Somali women living at northerly latitude.

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Background: The Mediterranean diet (MD) is widely recommended for the prevention of chronic disease, but evidence for a beneficial effect on bone health is lacking.

Objective: The aim of this study was to examine the effect of a Mediterranean-like dietary pattern [NU-AGE (New Dietary Strategies Addressing the Specific Needs of the Elderly Population for Healthy Aging in Europe)] on indexes of inflammation with a number of secondary endpoints, including bone mineral density (BMD) and biomarkers of bone and collagen degradation in a 1-y multicenter randomized controlled trial (RCT; NU-AGE) in elderly Europeans.

Design: An RCT was undertaken across 5 European centers.

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Background: Comparability of 25-hydroxyvitamin D (25(OH)D) measurements is hampered by method-related differences in measurement values. International standardization of laboratory assays has been suggested to solve this problem.

Methods: As part of the European Commission-funded project 'Food-based solutions for optimal vitamin D nutrition and health through the life cycle' (ODIN), original measurements of serum 25(OH)D of three German national health surveys conducted between 1998 and 2011 have been standardized retrospectively.

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Background: Evidence from randomized controlled trials (RCTs) for the causal role of vitamin D on noncommunicable disease outcomes is inconclusive.

Objective: The aim of this study was to investigate whether there are beneficial or harmful effects of cholecalciferol (vitamin D3) supplementation according to subgroups of remeasured serum 25-hydroxyvitamin D [25(OH)D] on cardiovascular and glucometabolic surrogate markers with the use of individual participant data (IPD) meta-analysis of RCTs.

Design: Twelve RCTs (16 wk to 1 y of follow-up) were included.

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This study investigated the effects of synthetic and natural sources of vitamin D biofortification in pig diets on pork vitamin D activity and pork quality. One hundred and twenty pigs (60 male, 60 female) were assigned to one of four dietary treatments for a 55 d feeding period. The dietary treatments were (1)50 μg vitamin D₃/kg of feed; (2)50 μg of 25-hydroxvitamin D₃/kg of feed (25-OH-D₃); (3)50 μg vitamin D₂/kg of feed; (4)50 μg vitamin D₂-enriched mushrooms/kg of feed (Mushroom D₂).

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This study investigates dietary fortification of heifer feeds with cholecalciferol and ergocalciferol sources and effects on beef total vitamin D activity, vitamer, respective 25-hydroxymetabolite contents, and meat quality. Thirty heifers were allocated to one of three dietary treatments [(1) basal diet + 4000 IU of vitamin D (Vit D); (2) basal diet + 4000 IU of vitamin D (Vit D); and (3) basal diet + 4000 IU of vitamin D-enriched mushrooms (Mushroom D)] for a 30 day pre-slaughter period. Supplementation of heifer diets with Vit D yielded higher (p < 0.

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The current study was aiming to report the prevalence of suboptimal vitamin D status among schoolchildren in Greece and investigate the role of sex, urbanisation and seasonality on vitamin D status. A sample of 2386 schoolchildren (9-13 years old) from four distinct prefectures was examined. The prevalence of 25-hydroxyvitamin D (25(OH)D) concentration <30 and <50 nmol/l (vitamin D deficiency and insufficiency respectively) was 5·2 and 52·5 %, respectively.

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Article Synopsis
  • The Vitamin D Standardization Program (VDSP) has created tools to help labs standardize tests for 25-hydroxyvitamin D, ensuring accuracy in laboratory results.
  • The paper outlines specific steps for labs to follow, including initial calibration and assessment of accuracy, which can apply to both commercial and in-house testing methods.
  • Labs are encouraged to maintain a total coefficient of variation (CV) of ≤10% and a mean bias of ≤5%, with guidance provided for achieving these goals using various approaches.
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Six laboratories associated with the Vitamin D Standardization Program (VDSP) participated in an interlaboratory comparison of LC with tandem MS (MS/MS) methods for the determination of 24,25-dihydroxyvitamin D3 [24,25(OH)2D3] in human serum. The laboratories analyzed two different serum-based Standard Reference Materials (SRMs) intended for use in the determination of 25-hydroxyvitamin D and 30 samples from the Vitamin D External Quality Assessment Scheme (DEQAS). All laboratory methods for 24,25(OH)2D3 were based on isotope dilution LC-MS/MS; three of the methods used derivatization of the vitamin D metabolites before LC-MS/MS.

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A systematic vitamin D fortification of fluid milk products and fat spreads was started in 2003 in Finland to improve vitamin D status. We investigated the effects of the vitamin D fortification policy on vitamin D status in Finland between 2000 and 2011. Serum 25-hydroxyvitamin D [S-25(OH)D] concentrations of a nationally representative sample comprising 6134 and 4051 adults aged ≥30 y from the Health 2000 and Health 2011 surveys, respectively, were standardized according to the Vitamin D Standardization Program with the use of liquid chromatography-tandem mass spectrometry.

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Measurement of serum 25-hydroxyvitamin D [25(OH)D] is considered the best indicator of vitamin D status. Two minor vitamin D metabolites are common interferences encountered in 25(OH)D assays. The first is 3-epi-25-hydroxyvitamin D [3-epi-25(OH)D], which if not chromatographically resolved from 25-hydroxyvitamin D [25(OH)D], can overestimate 25(OH)D concentrations.

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Background: Vitamin D deficiency may be a risk factor for mortality but previous meta-analyses lacked standardization of laboratory methods for 25-hydroxyvitamin D (25[OH]D) concentrations and used aggregate data instead of individual participant data (IPD). We therefore performed an IPD meta-analysis on the association between standardized serum 25(OH)D and mortality.

Methods: In a European consortium of eight prospective studies, including seven general population cohorts, we used the Vitamin D Standardization Program (VDSP) protocols to standardize 25(OH)D data.

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Background: Adolescents are a population group at high risk of low vitamin D status, yet the evidence base for establishing dietary vitamin D requirements remains weak.

Objective: The aim was to establish the distribution of vitamin D intakes required to maintain serum 25-hydroxyvitamin D [25(OH)D] concentrations above proposed cutoffs (25, 30, 40, and 50 nmol/L) during winter in white males and females (14-18 y of age) in the United Kingdom (51°N).

Design: In a dose-response trial, 110 adolescents (aged 15.

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Background: Vitamin D deficiency has been described as being pandemic, but serum 25-hydroxyvitamin D [25(OH)D] distribution data for the European Union are of very variable quality. The NIH-led international Vitamin D Standardization Program (VDSP) has developed protocols for standardizing existing 25(OH)D values from national health/nutrition surveys.

Objective: This study applied VDSP protocols to serum 25(OH)D data from representative childhood/teenage and adult/older adult European populations, representing a sizable geographical footprint, to better quantify the prevalence of vitamin D deficiency in Europe.

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Knowledge about the distributions of serum 25-hydroxyvitamin D (25(OH)D) concentrations in representative population samples is critical for the quantification of vitamin D deficiency as well as for setting dietary reference values and food-based strategies for its prevention. Such data for the European Union are of variable quality making it difficult to estimate the prevalence of vitamin D deficiency across member states. As a consequence of the widespread, method-related differences in measurements of serum 25(OH)D concentrations, the Vitamin D Standardization Program (VDSP) developed protocols for standardizing existing serum 25(OH)D data from national surveys around the world.

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