Research suggests that patients with low vitamin D levels are more likely than those with normal levels to suffer severe strokes and show poor recoveries.

Nils Henninger, assistant professor of neurology and psychiatry at University of Massachusetts Medical School and colleagues, studied measured blood levels of 25-hydroxyvitamin D, a marker of vitamin D status, in 96 stroke patients.

Overall, the area of dead brain tissue was twice as large in ischaemic stroke patients with low vitamin D levels (less than 30ng/ml) than those with normal levels.

In addition, each 10ng/ml reduction in vitamin D almost halved the likelihood of a healthy recovery in the three months following stroke, regardless of age or initial stroke severity.

“It’s too early to draw firm conclusions from our small study,” Dr Henninger says, “but ... if our findings are replicated, the next logical step may be to test whether supplementation can protect patients at high risk for stroke.”