Taking vitamin D supplements may lower blood pressure and boost exercise performance, Scots research has shown.
Volunteers given the vitamin daily for two weeks saw fitness improvements that allowed them to cycle longer with less exertion.
Their blood pressure and levels of the stress hormone cortisol were also lower compared with another group taking a dummy pill.
The Edinburgh research emerged two months after the independent Scientific Advisory Body on Nutrition (SACN) advisory group recommended all Scots should take vitamin D supplements because of the health implications of a lack of bright sunshine.
The body set up by the UK Government said the bleak British weather is stopping much of the population from receiving healthy amounts of the essential vitamin from sunlight – and natural food sources alone are not enough to boost levels.
It made the recommendation after studying the links between vitamin D levels and a range of health problems, including musculoskeletal health, heart disease, type 1 diabetes, cancer and multiple sclerosis.
More than one million people in Scotland are deficient in vitamin D, which is chiefly obtained from the action of sunlight on the skin.
In 2013, an Atlas of MS – produced by the Multiple Sclerosis International Federation – showed that the prevalence of the disease in Scotland was 188 cases per 100,000 people in the population, slightly behind Northern Ireland at 190 but higher than the 138 cases in Wales and 162 in England.
This revealed that, at that time, around 10,000 people were living with the condition in Scotland.
Researcher Dr Raquel Revuelta Iniesta, from Queen Margaret University in Edinburgh, said: “Our pilot study suggests that taking vitamin D supplements can improve fitness levels and lower cardiovascular risk factors such as blood pressure.“
The scientists plan to follow up the small study, which had just 13 participants, with a larger clinical trial looking at both healthy individuals and groups such as athletes and cyclists.
In the fitness test, volunteers taking vitamin D were able to cycle 6.5 kilometres in 20 minutes at the end of the two weeks compared with five kilometres at the start.
Despite cycling 30% further than participants given the inactive placebo, they showed lower signs of exertion.
Levels of the stress hormone cortisol were also lower in the urine of those taking the vitamin, which was given at a daily dose of 50 micrograms.
Previous studies have indicated that vitamin D blocks the action of an enzyme needed to make cortisol.
Large amounts of the hormone are thought to raise blood pressure by narrowing blood vessels and to stimulate the kidneys to retain water.
The findings were presented at the annual meeting of the Society for Endocrinology in Edinburgh.
Study lead author Dr Emad Al-Dujaili, also from Queen Margaret University, said: “Vitamin D deficiency is a silent syndrome linked to insulin resistance, diabetes, rheumatoid arthritis, and a higher risk for certain cancers.
“Our study adds to the body of evidence showing the importance of tackling this widespread problem.“