25-Hydroxyvitamin D Status and Anaerobic Performance in Female Collegiate Basketball Players
Professional athletes with adequate vitamin D status jumped higher and sprinted faster than those with insufficient status [<50nmol/L] (Close, 2012). The incidence of deficiency varies throughout the year, with rates increasing from 12% in the fall to 63% in the winter (Halliday 2011). This seasonal dip may adversely affect skeletal muscle function and performance.
PURPOSE: To evaluate serum vitamin D [25(OH)D3] status and anaerobic performance in collegiate female basketball players and verify whether 2000 IU/daily vitamin D3 is sufficient to maintain optimal 25(OH)D3 levels during the winter months.
METHODS: IRB approval was obtained prior to testing. Fifteen varsity female collegiate basketball players (age = 19.7 ± 1.4 y) volunteered to participate in the double blind, placebo-controlled study. Subjects were randomly divided into two groups: 1) 2000 IU vitamin D3/daily or 2) 100 IU vitamin E/daily (i.e. placebo). Supplements were consumed for 60 days. Health questionnaires, T drill sprint tests, and vertical jump heights were completed pre- and post-supplementation. Serum vitamin D concentrations 25(OH)D3 were measured pre- and post-supplementation using a 25(OH)D3 ELISA assay. SPSS t-tests were used for statistical analysis of data. Vitamin D deficiency was defined in accordance with the Endocrine Society guideline for inadequacy (<75 nmol/L).
RESULTS: 79% of the subject population was vitamin D insufficient in October (67.4±24.4 nmol/L). Serum 25(OH)D3 significantly increased in the vitamin D group following supplementation, with 72% of the subjects achieving levels greater than 75 nmol/L in December (67.9±24.2 nmol/L to 79.0±18.2 nmol/L, p<0.05). In contrast, serum 25(OH)D3 decreased in the placebo group, but changes were not significant (66.9±26.5 nmol/L to 56.7±26.5 nmol/L, p>0.05). The increase in serum 25[OH]D3 did not significantly affect vertical jump heights or T drill sprint times (p>0.05).
CONCLUSIONS: Daily supplementation of 2000 IU vitamin D3 over a 60-day period increased serum 25(OH)D3, but the elevated vitamin D status did not improve our chosen measures of anaerobic performance in collegiate female basketball players. The lack of performance effects may indicate that a chronic deficiency of vitamin D or a more severe deficiency is necessary to adversely affect muscle function.
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Research Advisor: Amy Olson, PhD, RDN, LD and Manuel Campos PhD, Biology Department