Title of the article: Effect of short-term Vitamin D supplementation on blood pressure, arterial health, and stress hormones in healthy volunteers

Background: Despite suggested epidemiological findings and plausible mechanisms, data linking vitamin D supplementation with improvement in cardiovascular risk is limited. Also, little is known about the effect of vitamin D on CVD health of young healthy people. Objectives: To investigate effect of short-term supplementation with vitamin D_3, considered to possess wide range of functions, on blood pressure (BP), Arterial compliance, body mass index (BMI) and salivary stress hormones levels in young healthy adults. Methods: Healthy, normotensive participants (n=20) were asked to consume 20µg/day of vitamin D3 for two weeks, and other volunteers received a placebo. BP, PWV, BMI and salivary cortisol level were assessed at baseline and after 2 weeks’ time. Vitamin D and total energy intakes were also evaluated. Results: There was a significant decrease in mean systolic BP by 5.3 ±6.46 mmHg (p=0.035), diastolic BP by 3.4±4.46 mmHg (p=0.002) and pulse wave velocity by 0.475±0.31m/s (p=0.007) with a negative correlation with vitamin D intake (r=−0.43). There was no significant effect on salivary cortisol (p=0.554), but salivary and urine cortisol/cortisone ratio was reduced from 0.952±0.54 to 0.784±0.68, p=0.028, and 1.71±0.75 to 1.22±0.53, p=0.015 respectively. Conclusions: Vitamin D3 intake decreases both diastolic and systolic BP and improves arterial compliance with reduction of urine and salivary cortisol/cortisone ratios indicating an inhibition of 11βHSD type 1 enzyme activity. The results suggest that vitamin D₃ could have the potential to reduce the risk of hypertension and cardiovascular diseases in young healthy adults and therefore support body functions in the event of Covid-19 infection. Further research is warranted to test the reproducibility of data.