Vitamin D and the Health of Blood Vessels in Kidney Disease

The Impact of Vitamin D Supplementation on Vascular Stiffness and Blood Pressure in Chronic Kidney Disease Patients

Individuals with kidney disease have a high risk of heart disease. This is not related to traditional risk factors, such as high blood pressure, high cholesterol or being overweight. A lack of vitamin D could be the reason why blood vessels become damaged and could explain the link between heart disease and kidney disease.

Most people living in Canada do not receive enough vitamin D from the sun or from the food they eat. When a person has kidney disease this is a particular problem as kidney disease stops what little vitamin D we do have being activated in the body. Low levels of activated vitamin D causes a domino effect with calcium and phosphate and all the hormones that control calcium and phosphate. Some people believe that this imbalance damages the blood vessels causing them to become stiff and inflexible (arterial stiffness) and this in turn could cause heart disease. In addition there are two different types of vitamin D that can be prescribed and it is currently not known whether there is any difference between the two types of vitamin D and the effect they have on the blood vessels.

The purpose of this study is to investigate whether providing vitamin D as a medication can have a direct affect on the stiffness of the blood vessels. The findings of this study will help both physicians and dietitians decide whether Vitamin D therapy is beneficial to patients and should help decide which type of Vitamin D is best to give to people with chronic kidney disease (CKD).

Inclusion Criteria:

• patients with an estimated glomerular filtration rate (eGFR) between 15 - 45 ml/min, and <2ml/min change in glomerular filtration rate (GFR) over the past 6 months
• treated with maximal conventional cardiovascular disease (CVD) risk reduction medications

Exclusion Criteria:

• patients with estimated glomerular filtration rate (eGFR) change of >2.1 ml/min over the past 6 months
• those who have terminal malignancies
• those with planned transplant within 6 months, or who are likely to commence renal replacement therapy (dialysis) within the 6 months after enrolment
• those with active infections or active inflammatory diseases (Systemic Lupus Erythematosus (SLE), vasculitis)
• those who refuse to give informed consent