Effect of vitamin D supplementation on serum 25(OH) D levels and blood pressure among the elderly in a nursing house: A double-blind, randomised placebo-controlled trial

Introduction: Hypertension is the most common cardiovascular disease, especially in the elderly. Previous studies have reported that vitamin D plays a role in blood pressure. This study aimed to analyse the effect of vitamin D supplementation on serum 25(OH)D levels and blood pressure. Methods: This was a double-blind, randomised placebo-controlled trial (RCT) on elderly subjects. Serum 25(OH)D levels were examined using chemiluminescent immunoassay (CLIA) method, while blood pressure was checked using a digital sphygmomanometer. Supplementation was given once per day for eight weeks; the control group was given a placebo, while the treatment group was given 2, 000 IU vitamin D₃ for subjects with insufficiency and 4, 000 IU for subjects with deficiency. Results: A total of 62 subjects aged 60–89 years participated and were randomised into 30 control and 32 treatment group subjects. Data analysis showed that vitamin D supplementation significantly increased 25(OH)D levels in treatment group (D=18.2±5.2 ng/mL) compared to control group (D=4.2±2.5 ng/mL) (p<0.001). However, vitamin D supplementation did not cause significant reduction in systolic blood pressure (D=-4.6(-25 - -0.5) mmHg for control group and D=-9.2(-20 - -27) mmHg for treatment group; p=0.109), and diastolic blood pressure (D=-7.2(-16 - -2) mmHg for control group and D=-8.4(-14.5 - -8.5) mmHg for treatment group; p=0.559). Conclusion: Vitamin D supplementation significantly increased serum 25(OH)D levels, but did not significantly reduce systolic and diastolic blood pressures in the elderly. Elderly people need to regularly check their vitamin D levels so that the provision of supplementation can be timely and their quality of life can be improved.