Low Vitamin D in Senior Citizens Signals Cognitive
Decline; Higher Parkinson’s Risk
An estimated 40 to 100% of seniors in U.S. and Europe
are deficient in vitamin D: linked to fractures, various chronic
diseases and death
July 12, 2010 - Senior citizens with low levels of
vitamin D are likely to experience declines in thinking, learning and
memory over a six-year period, according to a study in the July 12 issue
of Archives of Internal Medicine. Low levels of the vitamin may
also increase the risk for Parkinson's disease, according to a finding
that people with
higher levels of vitamin D appear to have a reduced risk of developing
Parkinson's disease. This study is in another of the JAMA/Archives
journals, Archives of Neurology.
Low Vitamin D Levels
Associated With Cognitive Decline
An estimated 40 to 100 percent of older adults in
the United States and Europe are deficient in vitamin D, according to
the article. This deficiency has been linked to fractures, various
chronic diseases and death.
Vitamin D may help prevent the degeneration of
brain tissue by having a role in formation of nervous tissue,
maintaining levels of calcium in the body, or clearing of beta-amyloid,
the substance that forms the brain plaques and tangles associated with
Alzheimer's disease.
Review of 28 studies finds the vitamin associated
with a substantial decrease in cardiovascular disease, type 2 diabetes
and metabolic syndrome for seniors and middle aged
Researchers also urging close monitoring of elderly
with hypertension during weather extremes; second study says thinking
ability varies with blood pressure
David J. Llewellyn, Ph.D., of University of Exeter,
England, and colleagues assessed blood levels of vitamin D in 858 adults
who were age 65 or older when the study began in 1998.
Participants completed interviews and medical
examinations and provided blood samples. At the beginning of the study
and again after three and six years, they repeated three tests of
cognitive function—one assessing overall cognition, one focusing on
attention and one that places greater emphasis on executive function, or
the ability to plan, organize and prioritize.
Participants who were severely deficient in vitamin
D (having blood levels of 25-hydroxyvitamin D of less than 25 nanomoles
per liter) were 60 percent more likely to have substantial cognitive
decline in general over the six-year period and 31 percent more likely
to experience declines on the test measuring executive function than
those with sufficient vitamin D levels.
"The association remained significant after
adjustment for a wide range of potential confounders and when analyses
were restricted to elderly subjects who were non-demented at baseline,"
the authors write. However, no significant association was seen for the
test measuring attention.
"If future prospective studies and randomized
controlled trials confirm that vitamin D deficiency is causally related
to cognitive decline, then this would open up important new
possibilities for treatment and prevention," the authors concluded
The study received funding from the Health Research
Council of New Zealand
Editorial says trials needed to check growing
claims for Vitamin D
Vitamins and Minerals: About Vitamin D
Vitamins are organic
substances (made by plants or animals), minerals are inorganic
elements that come from the earth; soil and water and are
absorbed by plants. Animals and humans absorb minerals from the
plants they eat. Vitamins and minerals are nutrients that your
body needs to grow and develop normally.
Vitamins and minerals have a
unique role to play in maintaining your health. For example
Vitamin D helps your body absorb the amount of calcium (a
mineral) it needs to form strong bones. A deficiency in vitamin
D can result in a disease called rickets (softening of the bones
caused by the bodies inability to absorb the mineral calcium.)
The body cannot produce calcium; therefore, it must be absorbed
through our food.
Other minerals like
chromium, copper, iodine, iron, selenium, and zinc are called
trace minerals because you only need very small amounts of them
each day. The best way to get enough vitamins is to eat a
balanced diet with a variety of foods. You can usually get all
your vitamins from the foods you eat.
About Vitamin D
Vitamin D is a fat-soluble
vitamin that is naturally present in very few foods, added to
others, and available as a dietary supplement. It is also
produced endogenously when ultraviolet rays from sunlight strike
the skin and trigger vitamin D synthesis. Vitamin D obtained
from sun exposure, food, and supplements is biologically inert
and must undergo two hydroxylations in the body for activation.
The first occurs in the
liver and converts vitamin D to 25-hydroxyvitamin D [25(OH)D],
also known as calcidiol. The second occurs primarily in the
kidney and forms the physiologically active
1,25-dihydroxyvitamin D [1,25(OH)2D], also known as calcitriol.
Vitamin D is essential for
promoting calcium absorption in the gut and maintaining adequate
serum calcium and phosphate concentrations to enable normal
mineralization of bone and prevent hypocalcemic tetany.
It is also needed for bone
growth and bone remodeling by osteoblasts and osteoclasts.
Without sufficient vitamin D, bones can become thin, brittle, or
misshapen. Vitamin D sufficiency prevents rickets in children
and osteomalacia in adults.
Together with calcium,
vitamin D also helps protect older adults from osteoporosis.
Vitamin D has other roles in
human health, including modulation of neuromuscular and immune
function and reduction of inflammation. Many genes encoding
proteins that regulate cell proliferation, differentiation, and
apoptosis are modulated in part by vitamin D. Many
laboratory-cultured human cells have vitamin D receptors and
some convert 25(OH)D to 1,25(OH)2D. It remains to be determined
whether cells with vitamin D receptors in the intact human carry
out this conversion.
"Vitamin D has been known for many years to play a
critical role in skeletal health, such that very low levels of this
hormone (less than 20 nanomoles per liter) can cause osteomalacia, a
disorder of impaired bone mineralization," write Andrew Grey, M.D., and
Mark Bolland, M.B.Ch.B., Ph.D., of University of Auckland, New Zealand,
in an accompanying editorial.
"More recently, observational studies have reported
inverse associations between levels of serum 25-hydroxyvitamin D, the
metabolite that best reflects overall vitamin D status, and the risk of
a wide range of disease, including cancer, vascular disease, infectious
conditions, autoimmune diseases, osteoporosis, type 2 diabetes mellitus
and obesity."
"The results of these observational studies have
prompted calls for widespread treatment of individuals with low levels
of vitamin D and the establishment of public health programs aimed at
raising the population levels of vitamin D to 'healthy' values," the
editorial states.
"It is now time to test the various hypotheses
generated by observational studies of vitamin D, including that of
Llewellyn et al, in adequately designed and conducted randomized
controlled trials.
"Very importantly, such trials will also provide an
opportunity to systematically assess potential harms of vitamin D
supplementation, an issue that has been largely overlooked or dismissed.
We should invest in trials that provide the best possible evidence on
the benefits and risks of vitamin D before we invest in costly,
difficult and potentially unrewarding interventional strategies."
Vitamin D Levels
Associated With Parkinson's Disease Risk
The study on Vitamin D and Parkinson’s disease
found that older people in the highest quartile (one-fourth of the study
population) of serum vitamin D levels had a 67 percent lower risk of
developing Parkinson's disease than those in the lowest quartile of
vitamin D levels.
Vitamin D is known to play a role in bone health
and may also be linked to cancer, heart disease and type 2 diabetes,
according to background information in the article in the July issue of
Archives of Neurology.
"Recently, chronically inadequate vitamin D intake
was proposed to play a significant role in the pathogenesis of
Parkinson's disease," the authors write.
"According to the suggested biological mechanism,
Parkinson's disease may be caused by a continuously inadequate vitamin D
status leading to a chronic loss of dopaminergic neurons in the brain."
Paul Knekt, D.P.H., and colleagues at the National
Institute for Health and Welfare, Helsinki, Finland, studied 3,173
Finnish men and women age 50 to 79 who did not have Parkinson's disease
at the beginning of the study, in 1978 to 1980.
Participants completed questionnaires and
interviews about socioeconomic and health background, underwent baseline
examinations and provided blood samples for vitamin D analysis.
Over a 29-year follow-up, through 2007, 50 of the
participants developed Parkinson's disease. After adjusting for
potentially related factors, including physical activity and body mass
index, individuals in the highest quartile (one-fourth of the study
population) of serum vitamin D levels had a 67 percent lower risk of
developing Parkinson's disease than those in the lowest quartile of
vitamin D levels.
"Despite the overall low vitamin D levels in the
study population, a dose-response relationship was found," the authors
write.
"This study was carried out in Finland, an area
with restricted sunlight exposure, and is thus based on a population
with a continuously low vitamin D status. Accordingly, the mean
[average] serum vitamin D level in the present population was about 50
percent of the suggested optimal level (75 to 80 nanomoles per liter).
Our findings are thus consistent with the hypothesis that chronic
inadequacy of vitamin D is a risk factor for Parkinson's disease."
The exact mechanisms by which vitamin D levels may
affect Parkinson's disease risk are unknown, but the nutrient has been
shown to exert a protective effect on the brain through antioxidant
activities, regulation of calcium levels, detoxification, modulation of
the immune system and enhanced conduction of electricity through
neurons, the authors note.
"In intervention trials focusing on effects of
vitamin D supplements, the incidence of Parkinson disease merits follow
up," they conclude
This work was supported by a National Institutes of
Health grant.
An editorial in same issue says study add to
study of neurological effects of vitamin D
The study is the first “longitudinal analysis of
vitamin D status as a risk of incident Parkinson's disease,” writes
Marian Leslie Evatt, M.D., M.S., of Emory University, Atlanta, in an
accompanying editorial.
"A growing body of basic research lends
plausibility to a role for adequate vitamin D status protecting against
development of Parkinson's disease," Dr. Evatt writes.
"Knekt and colleagues' study provides the first
promising human data to suggest that inadequate vitamin D status is
associated with the risk of developing Parkinson's disease, but further
work is needed in both basic and clinical arenas to elucidate the exact
role, mechanisms and optimum concentration of vitamin D in Parkinson's
disease."
Keep up with the latest news for senior citizens, baby
boomers
July 12, 2010 - Senior citizens with low levels of
vitamin D are likely to experience declines in thinking, learning and
memory over a six-year period, according to a study in the July 12 issue
of Archives of Internal Medicine. Low levels of the vitamin may
also increase the risk for Parkinson's disease, according to a finding
that people with
higher levels of vitamin D appear to have a reduced risk of developing
Parkinson's disease. This study is in another of the JAMA/Archives
journals, Archives of Neurology.
