Background and objectives: Evidence suggests associations between vitamin D deficiency and cardiovascular disease (CVD) risk factors, including hypertension and excessive cortisol levels. Also, vitamin D levels may impact 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 randomized placebo-controlled single-blinded parallel trial was conducted in healthy participants (n = 15). They received 2000 IU (50 µg) vitamin D3 per day (n = 9) or placebo (lactose) (n = 6) for 14 days. Body composition, systolic blood pressure (SBP), diastolic blood pressure (DBP) and arterial elasticity (as measured by pulse wave velocity, PWV) were recorded at baseline, day 7 and day 14 of intervention. A total of two 24-hour urine samples were collected to estimate free cortisol and cortisone levels. Exercise performance was assessed at the baseline and day 14 of the intervention using a bike ergometer in which BP and PWV were measured before and after exercise. The distance cycled in 20 minutes and the Borg Scale rate of perceived exertion (RPE) were recorded.
Results: In the intervention arm, at day 14, vitamin D supplementation significantly reduced SBP and DBP from 115.8 ± 17.1 and 75.4 ± 10.3 at baseline to 106.3 ± 10.9 (p = 0.022) and 68.5 ± 10.1 mmHg (p = 0.012) respectively. Also arterial stiffness was markedly reduced in the vitamin D group (from 7.45 ± 1.55 to 6.11 ± 1.89, p = 0.049). Urinary free cortisol levels and cortisol/cortisone ratio were significantly reduced from 162.65 ± 58.9 nmol/day and 2.22 ± 0.7 to 96.4 ± 37.2 (p = 0.029) and 1.04 ± 0.4 (p = 0.017) respectively. Exercise-induced SBP and DBP were significantly reduced post vitamin D intake from 130.7 ± 12.2 to 116.1 ± 8.1 (p = 0.012) and from 76.2 ± 8.4 to 70.5 ± 7.7 mmHg (p = 0.042) respectively. The distance cycled in 20 minutes significantly increased from 4.98 ± 2.65 to 6.51 ± 2.28km (p = 0.020), while the Borg Scale RPE 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.
Conclusion: These results suggest that daily vitamin D supplementation may ameliorate CVD risk factors including a decrease in 11β-HSD1 activity, as evidenced by the decrease in the cortisol/cortisone ratio, and improve exercise performance in healthy individuals. However, large scale studies are required to verify our findings.
Keywords: blood pressure; cardiovascular disease; exercise performance; oxidative stress; pulse wave velocity; vitamin D.