By Jeremy Appleton, ND, CNS
Healthnotes Newswire (February 8, 2007)—The Journal of the American Medical Association reports that multiple sclerosis risk can be lowered by high amounts of vitamin D, according to a new study that included more than 7 million active-duty US military personnel.
“Our results converge with a growing body of evidence supporting a protective role for vitamin D in MS development,” said Alberto Ascherio, MD, DrPH, Associate Professor of Nutrition and Epidemiology at the Harvard School of Public Health and an author of the study. “Vitamin D is a potent immune system modulator.”
Multiple sclerosis, or MS, is one of the most common neurological diseases affecting young adults. About 350,000 people in the United States and 2 million worldwide have the disease. MS symptoms vary unpredictably from person to person and from time to time in the same person. They can include fatigue, muscle weakness, vision problems, loss of balance and muscle coordination, slurred speech, tremors, stiffness, and bladder problems.
Symptoms are caused by a loss of the insulating myelin sheath that surrounds nerve fibers, which impairs the nerve fibers’ ability to transmit signals. MS is considered an autoimmune disease because myelin loss is the result of an inflammatory attack by the immune system, but what triggers the attack is unknown.
As researchers have accumulated more data about MS, some striking patterns have emerged: the disease is much more prevalent in higher latitudes, to both the north and the south. Because these locations get less sunlight, people who live there tend to have more problems with vitamin D deficiency (vitamin D is synthesized in the skin upon exposure to the sun’s ultraviolet light). Since vitamin D has hormone-like anti-inflammatory activity, researchers speculated that the heightened prevalence of MS in these regions could be due to vitamin D deficiency. It appears they were right.
The study identified 257 MS cases through Army and Navy physical disability records from 1992 through 2004; each was matched to two controls (people with similar characteristics—such as age, sex, ethnicity—but without the disease). Vitamin D status was determined by averaging levels of 25-hydroxyvitamin D (the circulating form of the vitamin) in two or more blood samples collected before the date of initial MS symptoms.
MS risk decreased with increasing blood levels of vitamin D. The association was not seen among blacks, but because there were fewer of them in the study, and because they tended to have substantially lower 25-hydroxyvitamin D levels, the study may have been inadequate for detecting an association in that group. Among whites, MS risk was cut nearly in half for those with the highest blood levels of vitamin D. The risk reduction was particularly strong for vitamin D levels measured before age 20.
Since food sources provide scant amounts of vitamin D, the main source for most people is through sun exposure. However, at latitudes of 42° or higher (for example, Boston, MA, or Detroit, MI), most ultraviolet radiation is absorbed in winter months by the atmosphere, and even extended sun exposure is inadequate to make enough vitamin D.
“A key question is whether it may be possible to reduce the incidence of MS in populations at high risk by increasing circulating levels of 25-hydroxyvitamin D,” said Dr. Ascherio. “However, until the efficacy of increasing vitamin D intake—either in the diet or with supplements—is proven for MS prevention, we cannot make broad recommendations.”
Jeremy Appleton, ND, CNS, is a licensed naturopathic physician, certified nutrition specialist, and published author. Dr. Appleton was the Nutrition Department Chair at the National College of Naturopathic Medicine, has served on the faculty at Bastyr University of Natural Health Sciences, and is a former Healthnotes Senior Science Editor and a founding contributor to Healthnotes Newswire. He has worked extensively in scientific and regulatory affairs in the supplement industry and is now a consultant through his company Praxis Natural Products Consulting and Wellness Services.
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