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Dr Saskia Wilson-Barnes


Postgraduate Research Assistant & Research Fellow

Academic and research departments

School of Biosciences and Medicine.

My publications

Publications

Smith TJ, Tripkovic L, Damsgaard, C, Mølgaard C, Ritz C, Wilson-Barnes SL, Dowling K, Hennessy A, Cashman K, Kiely M, Lanham-New SA, Hart KH (2016) Estimation of the dietary requirement for vitamin D in adolescents aged 14-18 years: a dose-response, double-blind, randomized placebo-controlled trial, The American Journal of Clinical Nutrition 104 (5) 138065 pp. 1301-1309 American Society for Nutrition
Background Adolescents are a population group at high risk of low vitamin D status, yet the evidence base for establishing dietary vitamin D requirements to ensure adequacy remains weak. Objective To establish the distribution of vitamin D intakes required to maintain serum 25- hydroxyvitamin D [25(OH)D] concentrations above proposed cut-offs (25, 30, 40 and 50 nmol/L) during the winter-time in white males and females (14-18 years) in the UK (51o 9 N). Design In a dose-response trial, 110 adolescents (age 15.9 ± 1.4 years; 43% male) were randomizedto receive daily 0, 10 or 20 µg vitamin D3 supplements for 20 weeks during the winter-time. A non-linear regression model was fit to the total vitamin D intake (diet plus supplemental) and post-intervention serum 25(OH)D concentrations, and regression predicted values were used to estimate the vitamin D intakes required to maintain serum 25(OH)D concentrations above specific cut-offs. Results Mean (± SD) serum 25(OH)D concentrations increased from 49.2 ± 12.0 to 56.6 ± 12.4 nmol/L and from 51.7 ± 13.4 to 63.9 ± 10.6 nmol/L in the 10 and 20 µg/day groups respectively, and decreased in the placebo group from 46.8 ± 11.4 to 30.7 ± 8.6 nmol/L (all p d 0.001). Vitamin D intakes required to maintain post-intervention 25(OH)D concentrations > 25 and > 30 nmol/L in 97.5% of adolescents were estimated as 10.1 and 13.1 µg/day respectively, and 6.6 µg/day to maintain 50% of adolescents > 40 nmol/L. As the response of 25(OH)D plateaued at 46 nmol/L, there is uncertainty in estimating the vitamin D intake required to maintain 25(OH)D > 50 nmol/L in 97.5% of adolescents, but it did exceed 30 µg/day Conclusions Vitamin D intakes of between 10 and ~30 µg/day are required by white adolescents during the winter-time in order to maintain serum 25(OH)D concentrations > 25 ? 50 nmol/L, depending on the serum 25(OH)D threshold chosen.

Vitamin D deficiency (Â25nmol/L) and insufficiency (Â50nmol/L) has become an increasingly popular topic. Current research focusses upon the potential ergogenic effects of vitamin D (vitD) in sporting performance; however, the relationship between vitD (dietary intake and nutritional status) and bone health within a University athlete cohort remains under-investigated. Therefore, the aims of this Thesis were to (1) examine vitD status longitudinally across the University competitive seasons and; (2) examine the implications that vitD deficiency/ insufficiency may have upon physical performance parameters or bone health.

In the first study, fifty-seven competitive University level- athletes from varied sports were observed from autumn to spring. Radial bone mineral density (BMD) and physical performance parameters were investigated; for the analysis of vitD and parathyroid hormone, blood samples were collected. Within the cohort 7% presented with deficiency during the autumn; increasing to 44% during spring. However, this did not have a significant effect upon physical performance and bone health despite an average status of 31.5±16.4 nmol/L in spring.

In the second study, 34 University athletes and sixteen sedentary students were recruited and followed from spring to summer. Whole body, hip and tibial scans were conducted to determine BMD and bone mineral content (BMC). Physical performance parameters including jump height, aerobic fitness, muscular strength and blood biochemistry were also collected. During the summer term, 26% of the cohort were vitD insufficient. Moreover, an insufficient vitD status was associated with a lowered jump height (p=0.015) but not aerobic fitness (p=0.07). There was also a significant positive relationship between vitD status, femoral neck BMC (r=0.685; pÂ0.02) and BMD (r=0.679; pÂ0.02). Our results show that BMD was higher in weight bearing athletes. The final study found that racket sport athletes had a significantly superior bone profile in their dominant arm when contrasted to controls.

Overall, these findings suggest that an insufficient vitD status was associated with lower indices of muscular power and aerobic fitness in University students. Therefore, being vitD replete may not only play an important role in musculoskeletal health but could also be a key determining factor in athletic performance.