|dc.description.abstract||Background: Accumulating evidence suggests a strong association between vitamin D status and cardiovascular disease (CVD) risk factors and exercise performance. Vitamin D deficiency promotes CVD risk factors including blood pressure (BP), arterial stiffness, oxidative stress and excessive cortisol levels. Moreover, vitamin D deficiency has been linked with receded exercise performance. However, studies investigating the effects of daily vitamin D supplementation on CVD risk factors and exercise performance are limited.
Objectives: To assess the effects of 2000IU (50μg) vitamin D3 supplementation on CVD risk factors including BP, oxidative stress, arterial stiffness and cortisol levels and exercise performance.
Methods: A randomised single blinded parallel study in which 13 normotensive subjects were randomly assigned to receive 2000IU (50μg) vitamin D3 supplementation or placebo for 14 days. BP and Pulse Wave Velocity (PWV) were obtained at baseline, day 7 and day 14 of intervention. Oxidative stress and cortisol levels were measured through 24 hour urine collections at the beginning and end of intervention. Exercise performance was measured at baseline and day 14 of intervention using a bike ergometer in which BP and PWV was measured before and after exercise. The distance cycled in 20 minutes was recorded and Borg rate of exertion scale was used.
Results: CVD risk factors were improved as systolic blood pressure (SBP) was significantly reduced from 115.35±17.01mmHg at baseline to 106.31±10.88mmHg (p=0.050) and diastolic blood pressure (DBP) was also significantly reduced from 79.12±13.76mmHg at baseline to 66.25±11.69mmHg (p= 0.012) post vitamin D supplementation. A small but non-significant reduction was noted in pulse wave velocity (PWV) in vitamin D subjects (p=0.085). Urine analysis showed no change in oxidative stress levels (p=0.690) but a significant reduction in urinary cortisol levels was noted as it reduced from 129.47±32.06μM at baseline to 105.79±37.42μM (p=0.029) in vitamin D subjects. However, no significant change in cortisone levels and cortisol/cortisone ratio was observed with vitamin D supplementation (p= 0.310, 0.514 respectively). Exercise performance was improved as SBP post exercise was significantly reduced from 128.23±14.67mmHg at baseline to 117.45±8.62mmHg after vitamin D supplementation. DBP was also reduced from 75.20±8.35mmHg at baseline to 70.12±7.28mmHg in vitamin D subjects. Vitamin D supplementation had no effect on PWV after exercise. Distance cycled in 20 minutes was significantly increased from baseline 4.98±2.65km to 6.51±2.28km (p=0.020) and Borg rate of exertion scale was significantly reduced from 5.13±1.36RPE to 4.25±0.71RPE (P= 0.021) with vitamin D supplementation. In placebo, no effect on CVD risk factors and exercise performance was observed.
Conclusion: Two week supplementation of 2000IU (50μg) of vitamin D has the potential to modify the CVD risk factors BP and cortisol. Vitamin D supplementation also effectively improves markers of exercise performance. However, the effects of short term vitamin D supplementation on other markers of CVD remains unanswered, thus more large scale studies are required.
Keywords: Vitamin D, cardiovascular disease, exercise performance, blood pressure, oxidative stress, arterial stiffness||