The report published in the American Journal of Clinical Nutrition showed no significant differences in the magnitude of the blood pressure reducing benefits of 800 IU or 2,000 IU doses per day, but the higher dose was found to decrease variability in systolic blood pressure, and high short term variability in blood pressure has been linked to damage to the heart, kidney and blood vessels.
“In this trial, a 2 year course of 2000 IU vitamin D/d did not show a greater benefit or harm in terms of BP reduction compared with a standard dose of 800 IU vitamin D/d among adults aged ≥ 60 y following total unilateral knee replacement,” wrote the researchers from University Hospital Zurich, Tufts University, Harvard School of Public Health, the University of Basel, Brigham and Women’s Hospital, and the University of Zurich.
“Notably, both treatment groups experienced a significant and similar reduction in day, night, and 24-h systolic and diastolic BP. Only in post hoc analysis, 2000 IU compared with 800 IU appeared to be significantly more effective in decreasing systolic BP variability by nearly 0.5 mm Hg, consistent with a 4.4% decrease.”
Data used in this study was obtained from the randomized, double blind, ancillary trial of the Zurich Multiple Endpoint Vitamin D Trial in Knee Osteoarthritis, which did not include a placebo group and included 250 adults aged 60+ who underwent elective surgery due to severe knee osteoarthritis; participants were randomly assigned to receive either 800 or 2000 IU of vitamin D3 daily for two years.
According to the research team the results showed that both groups experienced significant reductions in blood pressure and there were no significant differences between the groups; but when examining the systolic BP variability a significant reduction was seen in the high dose group when compared to the low dose group.
“In order to further explore BP control with regard to achieved 25(OH)D status, our observational study suggested that a target concentration of 28.7 ng/mL may be associated with maximal BP reduction, independent of treatment dose.”
“This study corroborates a plethora of cross-sectional and cohort analyses demonstrating low 25(OH)D status to be associated with elevated systolic BP and hypertension. However, whether low 25(OH)D concentration contributes to the risk of hypertension remains unclear.”
“While prospective studies have demonstrated poor 25(OH)D statue to be associated with high systolic BP, incident hypertension, and adverse cardiovascular events, there is an ongoing debate as to whether low 25 (OH)D concentrations cause incident hypertension or whether vitamin D supplementation can help in the treatments of hypertension.”
It was noted that several trials, some of which used high dose vitamin D, did not find an effect from vitamin D supplementation for reducing blood pressure in hypertensive adults. This study on the other hand adds to the growing body of scientific evidence that supports the myriad of health benefits afforded by vitamin D.
“Our study further suggests that, rather than the dosage of vitamin D supplementation, maintaining a moderate concentration of serum 25(OH)D might be most important,” write the study authors.
