A recent randomized controlled trial published in BMC Nephrology found no improvement in various markers of cardiovascular function in patients with chronic kidney disease on dialysis after supplementing with vitamin D.
Chronic kidney disease (CKD) describes loss of function of the kidneys over a minimum of three months. The disease progressively becomes more severe over time. People with severe CKD need treatment known as dialysis to keep them alive and healthy. Dialysis is a process that artificially removes waste and excess water from the blood in people with impaired kidney function.
People with CKD have an increased risk of cardiovascular disease. Past research shows that within CKD populations, low vitamin D levels are associated with poor cardiovascular markers like increased levels of B-type natriuretic peptide (BNP), increased cardiovascular events and increased mortality. BNP is a hormone that is secreted by heart ventricles when there are changes in pressure when heart failure develops. High concentrations of BNP means that the symptoms of heart failure are more severe.
Previous experimental research suggests that vitamin D treatment may reduce BNP levels, reduce left ventricular mass, and improve survival in dialysis patients. However, to date, no randomized controlled trials using parent compound vitamin D3 have been conducted to further evaluate these associations and experimental research.
Therefore, researchers of the present study wanted to see if they could help establish a causal relationship between vitamin D supplementation/levels and the health of the cardiovascular system in patients with CKD on dialysis.
They enrolled 50 men and women above the age of 18 years from the Dialysis Department and Outpatients’ Clinic of Renal Diseases of Holstebro Hospital who had CKD and who had been on dialysis treatment for more than three months. The patients were randomly assigned to receive either 3,000 IU of vitamin D or a placebo daily, for six months.
The researchers drew and measured cardiovascular health markers and vitamin D levels for both groups at baseline and then measured again after six months. The most important markers of cardiovascular health that they measured were 24 hour ambulatory blood pressure (24-h BP), arterial stiffness, levels of BNP, and cardiac function. The researchers wanted to know if higher vitamin D intake improved these markers in the patients with CKD after six months.
Here is what the researchers found:
- The vitamin D levels in the group receiving supplementation increased significantly from 11 ng/ml to 33.6 ng/ml, while there was no change in the placebo group (p<0.001).
- Although 24-h BP was reduced for both daytime and nighttime measurements over the six months in both groups, the difference between the reductions was insignificant.
- There was no significant change in arterial stiffness in either group.
- There was no significant change in levels of BNP in either group.
- Cardiac function improved in the group receiving vitamin D supplementation, but this improvement was insignificant.
This was the first randomized, placebo-controlled, double-blinded, study investigating the effects of vitamin D supplementation on cardiovascular function in dialysis patients. The researchers surmised a number of reasons as to why they did not see any significant improvements in the treatment group. For instance, previous prospective studies that showed benefits of vitamin D supplementation on markers of cardiovascular health in patients on chronic dialysis involved higher doses of vitamin D, as much as 2.4 times the dose used in the current study.
The researchers remained optimistic, concluding, “Certain subgroups could benefit from [vitamin D] supplementation. Further studies are warranted to evaluate this.”
There is still more research to be carried out in this field before we can come to any concrete conclusions. Future trials are needed to look at the effects of vitamin D on markers of cardiovascular health in a large population of patients on dialysis and using a dose that will bring the study group into a higher vitamin D range.