Compelling evidence that children with early symptoms of multiple sclerosis have low levels of vitamin D has emerged from a study by scientists in Canada.

The study of children suffering the first occurrence of the disease - often eye or sight problems - has found that those with insufficient amounts of the vitamin are far more likely to develop a full-blown case of MS than those who have normal levels.

The research in Canada follows evidence, revealed in The Times last week, that Scotland's poor health record has close links to vitamin D deficiency, which is caused by lack of exposure to sunshine. Scotland - in particular Orkney and Shetland, which get only a quarter of all available sunlight - is the world's hotspot for MS, closely followed by Canada.

The Canadian study raises the possibility that simply by taking a supplement every day from infancy it might be possible to prevent or slow the progression of the debilitating auto-immune disease, which at present has no definitive cause and is incurable.

Delegates at an international conference on multiple sclerosis in Montreal last week heard that the new evidence represents one of the most promising leads for both unravelling the cause of MS and treating it.

Brenda Banwell, one of the authors of the study, said she was implicating vitamin D insufficiency as a risk factor. She said: “People have been looking for things in the environment that might account for why Canada has such a high MS risk, and this is one of those factors.”

Researchers say large-scale clinical trials are needed to provide definitive proof that vitamin D should be used as a treatment and to determine how large the dosage should be.

Medical researchers have been studying the so-called “sunshine vitamin” for a possible link to MS because of the increased prevalence in high-latitude countries.

“There is a very consistent pattern of latitude and multiple sclerosis,” said Cedric Garland, an epidemiologist at the University of California in San Diego, who is writing a paper on the worldwide incidence patterns of the disease, comparing it to sunlight levels.

Oliver Gillie, the scientist and writer whose report on vitamin D deficiency, Scotland's Health Deficit: An Explanation and a Plan, was endorsed by world experts last week, said: “The Canadian findings are very exciting and raise the possibility of targeting children at risk of MS and preventing some of the disease.”

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