By Maggie Fox, Health and Science Editor

WASHINGTON, Sept 19 (Reuters) - Children later diagnosed with multiple sclerosis had far lower levels of vitamin D than other youngsters, Canadian researchers reported on Friday in studies showing more links between the "sunshine" vitamin and disease.

These were the first studies to show the effects in children, although others have shown that adults who live in northern latitudes, who get less sun exposure, may have a higher risk of MS.

They also support a growing body of studies that link low vitamin D levels with disease, including breast and colon cancer, heart disease, diabetes and tuberculosis.

Multiple sclerosis is a nervous system disease caused by damage to the myelin sheath that protects nerve cells. It affects 2.5 million people globally and can cause symptoms ranging from vague tingling to blindness and paralysis.

Vitamin D, made when skin is exposed to sunlight and found in fatty fish like salmon, is added to milk and other foods in many countries. Evidence suggests it helps lower blood pressure, reduce inflammation and boost the immune system.

Several studies presented at a meeting on MS in Montreal showed that children had low levels of the vitamin when they began to show evidence of the disease.

"Three-quarters of our subjects were below the optimal levels for vitamin D," said Heather Hanwell, a graduate student in nutritional sciences at the University of Toronto, who led one study.

Hanwell's team studied 125 children who had what is known as a demyelinating event -- evidence of damage to myelin that causes symptoms such as numbness. Blood was taken at the time.

Twenty of the children were diagnosed with MS within the next year, Hanwell said. Tests of the blood showed that 68 percent of those children had vitamin D insufficiency.

On average, the children with MS had much lower levels of the vitamin than children who did not experience any other MS-like symptoms.

Another study led by Dr. Brenda Banwell of Toronto's Hospital for Sick Children showed similar results.

"Seventeen of 19 children who had been diagnosed with MS had vitamin D levels below the target level," Banwell said in a telephone interview.

The next step is to see if giving vitamin D supplements prevents MS or helps relieve symptoms, Banwell said. She said it was not clear how lacking vitamin D might be linked with MS.

"Vitamin D acts as an immune modulator. On our immune cells there are what are known as receptors, a docking mechanism, for vitamin D," Banwell said. "In MS, there are many lines of evidence that immune cells are not regulated properly. One of the things that influences that balance is vitamin D."

Canadians have one of the highest rates of MS in the world, according to the Multiple Sclerosis Society of Canada. "In Canada for six months of the year the sun is not intense enough for us to manufacture vitamin D in our skin," Hanwell said. (Editing by Will Dunham and Peter Cooney)

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