Abstract
Background: Many New Zealanders have insufficient vitamin D status but the status of New Zealand athletes is unknown. Mood is important in the athletic environment as the response to training is partially dependent on psychological state, thus monitoring mood can help to prevent overtraining. The notion that vitamin D status affects mood is supported by animal studies but human research remains equivocal. There is an absence of randomised controlled trials exploring the relationship between vitamin D status and mood in athletes.
Objectives:
- To investigate the relationship, if any, between baseline vitamin D status and Brunel Mood Scale score in Otago and Southland semi-professional male rugby union players.
- To investigate whether vitamin D supplementation for 11 – 12 weeks significantly affects Brunel Mood Scale score in Otago and Southland semi-professional male rugby union players.
Design: This thesis presents results from a secondary data analysis of a randomised blinded placebo-controlled intervention trial in 57 male semi-professional rugby union players from Otago and Southland, New Zealand. Participants were allocated either 50000 IU vitamin D supplements or placebo fortnightly for 11 or 12 weeks. The Brunel Mood Scale questionnaire was completed at baseline and study endpoint.
Results: At study endpoint, serum 25(OH)D was significantly greater in the treatment group (113.56 ± 18.55 nmol/L) than the placebo group (79.62 ± 21.34), although both groups were vitamin D replete. There was a small negative correlation of -0.387 (p = 0.004) between BRUMS confusion and vitamin D concentrations at baseline. No other subscales were significantly correlated. There were no significant differences between treatment and placebo groups for change in Brunel Mood Scale subscale scores from baseline to weeks 11/12.
Conclusion: It is unlikely that vitamin D supplementation will affect mood in New Zealand semi-professional male rugby union players (who are vitamin D replete) and thus is unlikely to impact overtraining syndrome; thus supplementing with vitamin D for the sole purpose of bettering mood should be avoided. However, it remains unknown whether vitamin D supplementation would benefit those athletes with sub-optimal vitamin D status.