London, Nov 2 (IANS): Taking vitamin D supplements can improve exercise performance and lower the risk of heart disease, said a new study.

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.

"Our study suggests that taking vitamin D supplements can improve fitness levels and lower cardiovascular risk factors such as blood pressure," said study co-author Raquel Revuelta Iniesta from Queen Margaret University in Edinburgh.

In this study, researchers gave Vitamin D per day or a placebo over a period of two weeks to 13 healthy adults matched by weight 50 kg.

Adults supplementing with vitamin D had lower blood pressure compared to those given a placebo, and had 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 five km at the start of the experiment.

Despite cycling 30 percent further in the same time, the group taking vitamin D supplements also showed lower signs of physical exertion.

Previous studies suggest that vitamin D can block the action of enzyme 11-IHSD1, which is needed to make the "stress hormone" cortisol.

As Vitamin D may reduce circulating levels of cortisol, it could theoretically improve exercise performance and lower cardiovascular risk factors, the researchers explained.

The findings are scheduled to be presented at the ongoing Society for Endocrinology annual conference in Edinburgh.