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Study
Reports Possible Link
Between Vitamin D and Reduced MS Risk
Medical Update Memo
January 16, 2004
Summary
A new study in nurses suggests that those with higher vitamin
D intake may have had a reduced risk of developing multiple
sclerosis. The study included 187,563 women, including 173
with probable or definite MS, enrolled in the Nurses’ Health
Study, which regularly surveys female registered nurses in
the United States. Women whose intake of vitamin D was greater
than or equal to about 400 IU/day from supplements and food,
or from supplements alone, had a 40% lower risk of developing
MS than women who did not take vitamin D supplements. This
study adds new information to ongoing research focused on
a possible role for vitamin D in reducing the risk of developing
MS. There is no information in this study to determine whether
vitamin D affects the course of MS once it has begun. Further
research is necessary to clarify these findings. The normal
requirement for vitamin D is 200 to 400 IU daily for adults
and adolescents from both food and vitamin supplement sources.
Excessive intake of supplemental vitamin D can have serious,
toxic effects.
Details
A new study in nurses suggests that those with higher vitamin
D intake may have had a reduced risk of developing multiple
sclerosis. Kassandra Munger, MSc, and colleagues (Harvard
School of Public Health, University of California at Irvine)
reported their findings in the January 13, 2004 issue of
Neurology.
The cause of multiple sclerosis, which
involves immune attacks against the body’s own brain
and spinal cord tissues, is unknown. Worldwide, MS occurs more
frequently in countries that are further away from the equator,
such as Canada. It is thought that there may be genetic, infectious,
and environmental factors that increase or decrease an individual’s
risk of developing MS. One of several possible “protective”
factors which are being explored is the increased sunlight
exposure in areas closer to the equator and the resulting increase
in the body’s production of vitamin D.
Vitamin D is available not only through
sun exposure but also from nutritional sources and vitamin
supplementation. In general, vitamin D helps the body use calcium.
In addition, immune cells have been shown to be influenced
by vitamin D, and preliminary research suggests that vitamin
D can alter immune attacks in mice with MS-like disease. To
investigate the relation between vitamin D levels and the risk
for developing MS, the researchers used the database from the
Nurses’ Health Study I and Nurses Health Study II, which
regularly surveys female registered nurses about their history
of diseases and lifestyles.
For this study, the investigators focused
on dietary assessments from 187,563 of the participants. The
study included 173 women diagnosed with probable or definite
MS after their enrollment in the Study (between the ages of
30-55 for NHS I or 25-42 for NHS II). Vitamin D intake was
determined through the Nurses’ Health Study questionnaire
and four one-week diet records, which included queries about
diet and use of dietary supplements. Blood levels of vitamin
D were examined, and analyses were performed to determine other
factors that might affect the results, such as latitude of
the subject’s birthplace and smoking (members of this
research group reported an increased risk of MS among nurses
who smoked in the October 28, 2003 issue of Neurology).
Results
Women whose intake of vitamin D was greater than or equal to
about 400 IU/day (the amount usually contained in multivitamin
supplements), from either supplements – mostly multivitamins
– and food, or from supplements alone, had a 40% lower
risk of developing MS than those women who did not take vitamin
D supplements. No reduced risks were found for vitamin D intake
from food alone. Further analyses of smoking habits and birthplace
did not affect these results. There is no information in this
study to determine whether vitamin D affects the course of
MS once it has begun.
Importantly, vitamin D intake was strongly
associated with intake of other components of multivitamins,
including vitamins A and E and folic acid. Therefore, it was
not possible for the group to analyze the effects of vitamin
D intake independently from these other vitamins. The authors
note that the strongest evidence to date implicates vitamin
D, and suggest that this vitamin seems to be the most likely
candidate for association with reduced risk of MS.
This study adds new information to ongoing
research focused on a possible role for vitamin D in reducing
the risk of developing MS. Further research is necessary to
clarify these findings, for example: What is the role of vitamin
D versus other vitamins? Do these findings apply to men as
well? Can vitamin D alter the course of existing MS?
Research in Canada
A number of studies are underway or planned to investigate
possible association of sunlight exposure, vitamin D and
MS. In Canada, a study by Dr. Dessa Sadovnick, University
of British Columbia, and Dr. George Ebers, University of
Oxford, is underway on the vitamin D status in people with
MS and their families. They lead the world’s largest
MS genetic susceptibility study, which is funded by the MS
Scientific Research Foundation.
The normal requirement for vitamin D is
200 to 400 IU daily for adults and adolescents from both food
and vitamin supplement sources. This was the dosage taken by
participants in the study. The recommended dosage of 400 to
800 IU to prevent loss of bone density is considered a safe
therapeutic level. Excessive intake of supplemental vitamin
D can have serious, toxic effects on the body, including excessive
calcium levels in the blood, high blood pressure, nausea, anorexia,
impaired kidney function and kidney damage.
[Adapted from Research/Clinical Update,
National Multiple Sclerosis Society (USA)]
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Disclaimer
The Multiple Sclerosis Society of Canada is an independent,
voluntary health agency and does not approve, endorse or
recommend any specific product or therapy but provides information
to assist individuals in making their own decisions.
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