Background: Evidence suggests associations between vitamin D deficiency and cardiovascular risk factors, including hypertension and excessive cortisol levels. Also, vitamin D levels may be associated with exercise performance. Thus, we aimed to investigate the effects of vitamin D intake on cardiovascular risk factors, free urinary cortisol and exercise performance.
Methods: A randomised placebo controlled single-blinded parallel trial was conducted in healthy subjects. They received 2000 IU vitamin D3 per day (n=8) or placebo (n=5) for 14 days. Body composition, BP and arterial elasticity (PWV) were recorded at baseline, day 7 and day 14 of intervention. Two 24 h urine samples were collected to estimate free cortisol and cortisone levels. Exercise performance was assessed at baseline and day 14 of intervention using a bike ergometer in which BP and PWV were measured before and after exercise. The distance cycled in 20 min and Borg rate of exertion scale were recorded.
Results: In the intervention arm, vitamin D supplementation significantly reduced systolic and diastolic BP; from 114.65±16.41 and 78.58±12.65 to 105.41±11.12 (P=0.022) and 66.25±11.69 mmHg (P=0.014) respectively. However, PWV was only reduced slightly (P=0.085). Urinary free cortisol levels were significantly reduced from 162.59±58.9 to 96.4±37.25 nmol/day (P=0.044), and cortisol/cortisone ratio from 2.22±0.7 to 1.04±0.42 (P=0.017). Exercise-induced systolic and diastolic BP were significantly reduced post vitamin D intake from 128.2±14.67 to 117.45±8.6 (P=0.049) and from 75.20±8.35 to 70.12±7.28 mmHg (P=0.045) respectively. The distance cycled in 20 min significantly increased from 4.98±2.65 to 6.51±2.28 km (P=0.020), whilst the Borg rate of exertion scale reduced from 5.13±1.36 to 4.25±0.71 RPE (P=0.021). In the placebo arm, no significant effects on CVD risk factors and exercise performance were observed.
Conclusions: These results suggest that daily vitamin D supplementation may ameliorate CVD risk factors including a decrease in 11β-HSD 1 activity and improve exercise performance in healthy individuals. However, large scale studies are required to verify our findings.