People with low vitamin D levels may have a higher risk of developing the nerve disease multiple sclerosis (MS).
MS is believed to result from the body’s own immune system attacking nerve cells’ protective coating, or myelin sheath. The resulting damage can affect vision, hearing, memory, balance and mobility.
In a recent study, researchers with the Harvard School of Public Health in Boston looked for MS cases among seven million U.S. Army and Navy personnel who had blood samples stored in a special repository. Blood samples from 257 people who developed MS were compared with those from personnel who did not have the disease.
The results indicate MS risk decreases with increasing levels of vitamin D in the blood. Among white people, for example, individuals in the top fifth of vitamin D concentration had a 62 per cent lower risk of developing MS than individuals in the lowest fifth of vitamin D concentration. Vitamin D is found in foods such as fortified milk and fatty fish, and is also made in the skin after exposure to sunlight.
“The results imply that people with higher vitamin D levels have a lower risk of developing MS,” says Dr. Alberto Ascherio, the study’s senior author.
“There are two explanations,” Ascherio says. “One is that having high vitamin D levels truly protects you from MS – so you’re protected by the vitamin D itself. The alternative is the vitamin D level is the marker for something else. Perhaps the most important concern is light exposure itself: It’s possible sunlight has some effects that go beyond production of vitamin D, in which case if you took vitamin D in the form of supplements, perhaps you wouldn’t be as protected as by exposing yourself to sunlight directly.”
Because of this uncertainty, Ascherio says more research is needed before broad recommendations can be made about whether vitamin D levels should be increased, and how they should be increased.