Link Between MS And Sunlight Studied
As reported by ScienceDaily Exploring the Link Between Sunlight and Multiple Sclerosis (3/10)
For more than 30 years, scientists have known that multiple sclerosis (MS) is
much more common in higher latitudes than in the tropics. Because sunlight is
more abundant near the equator, many researchers have wondered if the high
levels of vitamin D engendered by sunlight could explain this unusual pattern
Vitamin D may reduce the symptoms of MS, says Hector DeLuca, Steenbock Research
Professor of Biochemistry at University of Wisconsin-Madison, but in a study
published in Proceedings of the National Academy of Sciences, he and first
author Bryan Becklund suggest that the ultraviolet portion of sunlight may play
a bigger role than vitamin D in controlling MS.
Multiple sclerosis is a painful neurological disease caused by a deterioration
in the nerve's electrical conduction; an estimated 400,000 people have the
disabling condition in the United States. In recent years, it's become clear
the patients' immune systems are destroying the electrical insulation on the
The ultraviolet (UV) portion of sunlight stimulates the body to produce vitamin
D, and both vitamin D and UV can regulate the immune system and perhaps slow
MS. But does the immune regulation result directly from the UV, indirectly from
the creation of vitamin D, or both?
The study was designed to distinguish the role of vitamin D and UV light in
explaining the high rate of MS away from the equator, says DeLuca, a world
authority on vitamin D. "Since the 1970s, a lot of people have believed that
sunlight worked through vitamin D to reduce MS," says DeLuca. "It's true that
large doses of the active form of vitamin D can block the disease in the animal
model. That causes an unacceptably high level of calcium in the blood, but we
know that people at the equator don't have this high blood calcium, even though
they have a low incidence of MS. So it seems that something other than vitamin
D could explain this geographic relationship."
Using mice that are genetically susceptible to MS-like disease, the researchers
triggered the disease by injecting a protein from nerve fibers. The researchers
then exposed the mice to moderate levels of UV radiation for a week. After they
initiated disease by injecting the protein, they irradiated the mice every
second or third day. The UV exposure (equivalent to two hours of direct summer
sun) did not change how many mice got the MS-like disease, but it did reduce
the symptoms of MS, especially in the animals that were treated with UV every
other day, DeLuca says.
The research group also found that although the UV exposure did increase the
level of vitamin D, that effect, by itself, could not explain the reduced MS
symptoms. In some situations, radiation does reduce immune reactions, but it's
not clear what role that might play in the current study. "We are looking to
identify what compounds are produced in the skin that might play a role, but we
honestly don't know what is going on," DeLuca says. "Somehow it makes the
animal either tolerate what's going on, or have some reactive mechanism that
blocks the autoimmune damage."
MS is a progressive neurological disease with few effective treatments, but
DeLuca stresses that the study, however hopeful, may or may not lead to a new
mode of treatment. "There are several ways this could go. If we can find out
what the UV is producing, maybe we could give that as a medicine. In the short
term, if we can define a specific wavelength of light that is active, and it
does not overlap with the wavelengths that cause cancer, we could expose
patients who have been diagnosed with MS to that wavelength." Does this
information change the common prescription to avoid excessive sun exposure? "If
you have an early bout with MS, then you have to think about your options,"
says DeLuca. "Remember, this is just experimental work at this stage. Whether
it can be translated into practical applications on MS remains to be seen."
Low Levels Of Vitamin D Linked To Muscle Fat, Decreased Strength In Young People
There's an epidemic in progress, and it has nothing to do with the flu. A
ground-breaking study published in the March 2010 Journal of Clinical
Endocrinology and Metabolism found an astonishing 59 per cent of study subjects
had too little Vitamin D in their blood. Nearly a quarter of the group had
serious deficiencies (less than 20 ng/ml) of this important vitamin. Since
Vitamin D insufficiency is linked to increased body fat, decreased muscle
strength and a range of disorders, this is a serious health issue.
"Vitamin D insufficiency is a risk factor for other diseases," explains
principal investigator, Dr. Richard Kremer, co-director of the Musculoskeletal
Axis of the Research Institute of the MUHC. "Because it is linked to increased
body fat, it may affect many different parts of the body. Abnormal levels of
Vitamin D are associated with a whole spectrum of diseases, including cancer,
osteoporosis and diabetes, as well as cardiovascular and autoimmune disorders."
The study by Dr. Kremer and co-investigator Dr. Vincente Gilsanz, head of
musculoskeletal imaging at the Children's Hospital Los Angeles of the
University of Southern California, is the first to show a clear link between
Vitamin D levels and the accumulation of fat in muscle tissue - a factor in
muscle strength and overall health. Scientists have known for years that
Vitamin D is essential for muscle strength. Studies in the elderly have showed
bedridden patients quickly gain strength when given Vitamin D.
The study results are especially surprising, because study subjects - all
healthy young women living in California - could logically be expected to
benefit from good diet, outdoor activities and ample exposure to sunshine - the
trigger that causes the body to produce Vitamin D. "We are not yet sure what is
causing Vitamin D insufficiency in this group," says Dr. Kremer who is also
Professor of Medicine at McGill University. High levels of Vitamin D could help
reduce body fat. Or, fat tissues might absorb or retain Vitamin D, so that
people with more fat are likely to also be Vitamin D deficient."
The results extend those of an earlier study by Dr. Kremer and Dr. Gilsanz,
which linked low levels of Vitamin D to increased visceral fat in a young
population. "In the present study, we found an inverse relationship between
Vitamin D and muscle fat," Dr. Kremer says. "The lower the levels of Vitamin D
the more fat in subjects' muscles."
While study results may inspire some people to start taking Vitamin D
supplements, Dr. Kremer recommends caution. "Obviously this subject requires
more study," he says. "We don't yet know whether Vitamin D supplementation
would actually result in less accumulation of fat in the muscles or increase
muscle strength. We need more research before we can recommend interventions.
We need to take things one step at a time."
This study was funded by a grant from the National Institutes of Health, the
U.S, Department of the Army, the Canadian Institutes of Health Research (CIHR),
the Natural Sciences and Engineering Research Council of Canada (NSERC) and the
Dimensional Fund Advisors Canada Inc (a subsidiary of U.S.-based Dimensional