Taking vitamin D supplements can improve exercise performance and lower the risk of heart disease, according to the findings of a preliminary study presented at the Society for Endocrinology annual conference in Edinburgh.
Vitamin D, which is both a vitamin and a hormone, helps control levels of calcium and phosphate in the blood and is essential for the formation of bones and teeth. Sources of Vitamin D include oily fish and egg yolks, but it can be difficult to get enough through diet alone. Most people generate vitamin D by exposing their skin to ultraviolet B rays in sunlight.
Previous studies suggest that vitamin D can block the action of a particular enzyme needed to make the stress hormone cortisol. High levels of cortisol may raise blood pressure by restricting arteries, narrowing blood vessels and stimulating the kidneys to retain water. As vitamin D may reduce circulating levels of cortisol, it could theoretically improve exercise performance and lower cardiovascular risk factors.
In this small study, researchers from Queen Margaret University in Edinburgh gave 13 healthy adults matched by age and weight 50 μg (2000 IU) of vitamin D per day or a placebo over a period of two weeks.
Adults supplementing with vitamin D had lower blood pressure compared to those given a placebo, as well as having lower levels of the stress hormone cortisol in their urine. A fitness test found that the group taking vitamin D could cycle 6.5 km in 20 minutes, compared to just 5 km at the start of the experiment. Despite cycling 30% further in the same time, the group taking vitamin D supplements also showed lower signs of physical exertion.
This short-term pilot study, although very small, suggests that taking vitamin D supplements can improve fitness levels and lower cardiovascular risk factors such as blood pressure. The researchers said the next step is to perform a larger clinical trial for a longer period of time in both healthy individuals and large groups of athletes such as cyclists or long-distance runners.
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