A new study published in Journal of Clinical Endocrinology and Metabolism has found that vitamin D relates to endothelial function in elderly women, but not elderly men.
Endothelial dysfunction is defined by a lack of balance between dilation and constriction of blood vessels. In otherwise healthy blood vessels, the endothelial cells (those that line the inside of blood vessels) act to regulate processes such as coagulation, immune function, and platelet adhesion. Non-functioning endothelial cells can increase the risk of or be caused by certain cardiovascular diseases such as hypertension and coronary artery disease.
Recent research continues to provide evidence that vitamin D plays a role in endothelial function. Observational studies tend to show vitamin D deficient populations are more at risk for arterial stiffness and endothelial dysfunction, while a few trials have found that vitamin D supplementation improves markers of endothelial function, such as flow-mediated dilation.
To date, the literature has focused on populations of young and middle-aged adults, and has not examined the relationship between vitamin D and endothelial function in elderly populations. This area of research is important for older individuals as aging increases the risk for both vitamin D deficiency and cardiovascular disease.
Recently, a research team led by Dr. Marcello Maggio conducted a study on the relationship between vitamin D and endothelial function among a sample of elderly individuals.
They looked at the data from 852 participants from the Prospective Study of the Vasculature in Uppsala Seniors (PIVUS) Study. The PIVUS Study was conducted between 2001 and 2004 in order to examine different areas of endothelial and arterial function among a sample of 1,000 individuals aged 70 years old living in Sweden.
For the current study, the research team collected data on the participants’ vitamin D levels as well as markers of endothelial function. The main markers of endothelial function the researchers measured were endothelium-dependent vasodilation (EDV) and endothelium-independent vasodilation (EIDV).
EDV is the relaxation of blood vessels caused nitric oxide produced by endothelial cells. EIDV is the relaxation of blood vessels in which nitric oxide originates from another source besides the endothelial cells and induces relaxation in the blood vessels. A higher degree of vasodilation in either EDV or EIDV are indicators of better relaxation and improved endothelial function.
To measure EIDV, the researchers administered a common drug which acts to release nitric oxide into the blood vessels which induces vasodilation.
One of the techniques that the researchers utilized to measure EDV is known as forearm blood flow. Forearm blood flow involves an evaluation of resting blood flow followed by administration of an organic molecule into the arteries which naturally causes endothelial cells to produce nitric oxide.
After their analysis, here is what the researchers found:
- The average vitamin D levels for men and women were 23.32 ng/ml and 22.8 ng/ml, respectively.
- There was a significant positive relationship between vitamin D and EIDV among women, meaning that higher vitamin D levels were associated with improved EIDV.
- After adjusting for confounding variables, the positive relationship between vitamin D and EIDV among women remained significant.
- There was no significant relationship between vitamin D and EDV among women.
- There was no significant relationship between vitamin D and EIDV or EDV among men.
The researchers concluded,
“In older women, but not in men, vitamin D concentration was positively and independently associated with endothelium-independent vasodilation.”
The researchers note that the observational design of their study means that it cannot be determined if vitamin D causes improved EIDV. Furthermore, the study population consisted of elderly individuals living in Sweden and therefore the results cannot be generalized to other populations.
The research presented here adds to the evidence for vitamin D’s role in endothelial function and cardiovascular health. The study provides interesting results in that it suggest that this relationship exists only applies to EIDV among older females.
Further research is needed to clarify if a sex-specific role for vitamin D in endothelial function exists, and future trials are needed to determine if correcting for vitamin D deficiency with supplementation improves endothelial function among older individuals.