June 7, 2009
Children who develop multiple sclerosis have substantially lower levels of vitamin D than children who do not develop the disease, according to a series of studies presented at an international conference on multiple sclerosis in Montreal.
Multiple sclerosis is a degenerative disease of the nervous system in which the myelin sheath that insulates nerve cells breaks down, leading to problems in the transmission of nervous signals. Symptoms can range from tingling and numbness to tremors, paralysis or blindness. An estimated 2.5 million people around the world suffer from the disease, which is rarely diagnosed before the age of 15.
In one study, researchers from the University of Toronto tested the vitamin D blood levels of 125 children who had exhibited symptoms indicating some form of damage to the myelin sheath.
“Three-quarters of our subjects were below the optimal levels for vitamin D,” lead researcher Heather Hanwell said.
After a year, the researchers compared the data from the 20 children who had since been diagnosed with multiple sclerosis with those who had not exhibited any further demyelinating symptoms. They found that the average vitamin D levels of children who had been diagnosed with multiple sclerosis were substantially lower than those of the other children. Among the diagnosed children, 68 percent of children were actually deficient in the vitamin.
A similar study was conducted by researchers from Toronto’s Hospital for Sick Children.
“Seventeen of 19 children who had been diagnosed with MS had vitamin D levels below the target level,” researcher Brenda Banwell said.
Researchers have suspected a connection between vitamin D and multiple sclerosis for many years, ever since discovering that the disease is more common at more northern latitudes. Because the body synthesizes vitamin D upon exposure to sunlight, deficiency is much more common in places where the sun is weaker, especially during the winter.
“There is a very consistent pattern of latitude and multiple sclerosis,” said epidemiologist and multiple sclerosis researcher Cedric Garland of the University of California-San Diego.
Hanwell directly linked Canada’s northern latitude to its high rates of multiple sclerosis.
“In Canada for six months of the year the sun is not intense enough for us to manufacture vitamin D in our skin,” she said.
Canada has one of the highest multiple sclerosis rates in the world. One of the few countries with a higher rate is Scotland, which has regions reached by only a quarter of all available sunlight. Recent research has confirmed a strong connection in Scotland between vitamin D deficiency and poor health status.
“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,” Banwell said.
It remains unclear exactly how vitamin D might influence multiple sclerosis risk, but researchers believe it may have to do with the immune system. New research continues to illuminate the role that vitamin D plays in the immune system, providing protection against cancer, tuberculosis and autoimmune diseases.
Many health researchers believe that multiple sclerosis is an autoimmune disease.
“Vitamin D acts as an immune modulator,” Banwell said. “On our immune cells there are what are known as receptors, a docking mechanism, for vitamin D. In MS, there are many lines of evidence that immune cells are not regulated properly.”