Vitamin D from Sun Exposure May Decrease Multiple Sclerosis Risk
Multiple sclerosis is a chronic, often disabling disease that attacks the central nervous system. It is thought to be an autoimmune disorder in which the body’s defense system attacks myelin, the fatty substance that surrounds and protects nerve fibers. The cause of MS is not entirely known, but scientists believe a combination of several factors is likely involved – including vitamin D levels and exposure to the sun.
Sun Exposure Decreases MS Risk Independently of Vitamin D Levels
Multiple sclerosis prevalence increases the further a person lives from the equator, so epidemiologists are interested in how the sun may affect disease risk and other factors that may be involved with the phenomenon. Vitamin D, a nutrient that the body produces from sunlight, is noted to likely have a positive impact on the immune system and therefore may help protect against the autoimmune disease.
Robyn Lucas PhD of the Australian National University and colleagues studied 216 people between the ages of 18 and 59 who had not been diagnosed with MS, but who were experiencing some of the first symptoms of the disease. These volunteers were matched with 395 healthy controls that were of similar ages and from the same four regions of Australia.
Each participant was surveyed on how much sun they were exposed to during different periods of their lives. The researchers also measured the amount of skin damage each had related to sun exposure and the amount of melanin in the skin. Vitamin D levels were measured by blood test.
Researchers also gathered data on physical activity level, smoking history and the use of dietary supplements.
The risk of having a “first demyelinating event” (FDE), symptoms that precede the diagnosis of multiple sclerosis, decreased by 30 percent for each UV increase of 1,000 kilojoules. Patients with the most evidence of skin damage from sun exposure were 60% less likely to be diagnosed than those with the lowest levels.
Patients with the highest vitamin D levels were also 5 to 10% less likely to have multiple sclerosis symptoms versus those with the lowest levels.
“Added together, the differences in sun exposure, vitamin D levels and skin type accounted for a 32-percent increase in a diagnosed first event from the low to the high latitude regions of Australia,” Lucas said. But scientists still need to study sun exposure separately from vitamin D levels to get a better overall picture of multiple sclerosis risk reduction.
She does warn patients to continue limiting sun exposure due to the increased risk of skin cancer. Lucas also advises against people using tanning beds as the risks far outweigh any possible protective effect against MS.
About 350,000 people in the United States suffer from MS. Women are twice as likely as men to get the disease.
Source Reference: Neurology. 2011;76:540-548.