25(OH)D Levels and Athletic Performance in Division III Female Cross Country/Indoor Track and Field Runners
Purpose: to examine the association between 25(OH) vitamin D3 [25(OH) D3] and iron status and anaerobic and aerobic athletic performance in female cross country runners.
Methods: Approval was obtained from the Institutional Review Board; a total of 29 participants started cross country in the fall and 15 participants continued with track in the spring. The participants' age ranged from 18 to 22. Blood collections and performance tests were performed three times throughout the year, in August, October, and January. Serum ferritin and 25(OH) D3 were measured using ELISA kits. Hemoglobin was measured using a hand-held hemoglobin analyzer. Runners completed a 2.5 mile time trial to assess aerobic performance and a 20 meter sprint, a vertical jump test and four repetition vertical jump test to assess anaerobic performance. Three-day diet records were evaluated using Diet Analysis Plus 9.0 at the beginning of the study. Average daily solar radiation [SR ave.] one month prior to evaluation periods was obtained from National Climatic Data Center.
Results: Serum 25(OH)D3 values declined greatly from August to January with mean values of 191±75 in August, 110±18 in October, and 64±14 nmol/L in January. Serum ferritin values were for August 59±40, October 35±17, and January 48±21 ng/mL and hemoglobin levels were for August 13.0±1.2, October 12.9±1.0, and January 13.7±1.0 g/dL. Dietary vitamin D intake average was 5.2 mcg/day and dietary iron intake average was 17.6 mg/day. Five participants were consuming vitamin D supplements ranging from 500 IU to 2000 IU. Adequate 25(OH)D3 levels (≥75 nmol/L) were maintained in 100% of participants in August, 86% in October, and 14% in January. Decrease in SR ave. significantly correlated (r=0.983) to a decline in 25(OH)D3 levels. Anaerobic performance measurements displayed no significant difference from August to January in 4 jump (2.08±0.28 and 2.05±0.30) (p=0.583), mean power (830.7±126.1 and 839.2±109.0 W) (p=0.663), 20 m sprint (3.03±0.14 and 3.08±0.15 s) (p=0.066), and vertical jump (0.41±0.07 and 0.41± 0.08 m) (p=0.577), but did show a significant decrease in time trail results (17:06±0.04 and 16:32±0.03) (p=0.003).
Conclusions: there was a strong correlation [r = 0.983] between solar radiation and serum 25(OH)D3 values. Serum 25(OH)D3 decreased significantly from fall to winter months in this population despite adequate dietary intake of vitamin D. Although 25(OH)D3 levels decreased, anaerobic performance was not significantly affected. However, aerobic measurements significantly decreased suggesting a possible relationship between aerobic performance and 25(OH)D3 levels.
Katie Jepperson, Katie Schwarz and Tyler Etheridge [pictured below] presenting their research at the Northland Chapter of the American College of Sports Medicine, April 1, 2011
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