| Popis: |
British swimmers are at a heightened risk of vitamin D deficiency (serum 25-hydroxyvitamin D (25(OH)D): − 1) as their large indoor training volumes often restrict sunlight exposure, especially during the winter when daylight hours are reduced. Previous research has recommended 4000 IU∙day− 1 vitamin D3 from October to March to offset vitamin D losses. However, no current study has analysed this approach over multiple seasons to assess if this is an appropriate strategy. Twenty-nine world-class British swimmers (aged 16–30 years) provided a 10 mL venous blood sample as part of their routine haematological screening in the September of three consecutive years (2018, 2019, 2020). Serum 25(OH)D was determined by radioimmunoassay and this result determined the length of the standardised vitamin D3 protocol (− 1: 4000 IU∙day− 1 from September to March, 30–79 nmol∙L− 1: 4000 IU∙day− 1 from October to March, > 75 nmol∙L− 1: no supplementation). Mean serum 25(OH)D concentrations increased each year (2018: 76.4 ± 28.4 nmol∙L− 1, 2019: 91.5 ± 24.8 nmol∙L− 1, 2020: 115.0 ± 36.6 nmol∙L− 1, p 125 nmol∙L− 1, although it is currently debated whether this is a concern or a benefit for athletic populations. Supplementing with 4000 IU∙day− 1 of vitamin D3 throughout the winter can therefore increase the vitamin D status of swimmers. However, more frequent testing may be required to ensure that serum 25(OH)D remains within the sufficient across the season (75–125 nmol∙L− 1). |
