Boosting vitamin D may stave off symptoms of multiple sclerosis (MS) in early stages of the disease, research has shown.
Scientists found that levels of the vitamin were strongly linked to disease severity and speed of progression.
The findings, published in the journal JAMA Neurology, suggest that vitamin D supplements may provide a simple treatment approach for newly diagnosed patients with MS.
"Because low vitamin D levels are common and can be easily and safely increased by oral supplementation, these findings may contribute to better outcomes for many MS patients," said lead research Professor Alberto Ascherio, from the Harvard School of Public Health in the US.
Around 2.5 million people around the world are thought to have MS, an autoimmune disease which attacks the insulating material around nerve fibres.
Symptoms can range from mild tingling sensations to crippling paralysis.
The scientists analysed data from 465 MS patients in 18 European countries, as well as Israel and Canada who were taking part in a trial looking at the effectiveness of treatment with the drug interferon beta-1b .
Vitamin D levels were measured at the onset of symptoms and at regular intervals over a 24-hour period. The results were then compared with the progress of patients over a five years.
Early stage MS patients who had adequate levels of vitamin D were 57% less likely than those with low levels to develop new brain lesions - areas of nerve damage. They also had a 57% lower relapse rate and a 25% reduced yearly increase in lesion size.
Loss of brain volume, an important predictor of disability, was also less pronounced among patients with adequate levels of vitamin D.
"The benefits of vitamin D appeared to be additive to those of interferon beta-1b, a drug that is very effective in reducing MS activity," Prof Ascherio added.
"The findings of our study indicate that identifying and correcting vitamin D insufficiency should become part of the standard of care for newly diagnosed MS patients."