Foliumzuur
tegen de ziekte van Alzheimer.*
Uit
een groot en zeer langdurig onderzoek in Amerika blijkt dat foliumzuur de kans
op Alzheimer flink kan verminderen. Foliumzuur zit vooral in fruit,
peulvruchten, noten, groene bladgroente en lever. Over het algemeen krijgen
mensen te weinig foliumzuur binnen door slechte eetgewoontes of omdat veel
tijdens de bereiding van het eten verloren gaat. De meeste mensen kunnen daarom
de aanbevolen dagelijkse dosis van 400 microgram/dag alleen bereiken door
supplementering, dan verlaagt de kans op het ontstaan van Alzheimer wel met 55%.
Andere vitamines of antioxidanten lijken geen verschil te maken in het ontstaan
van de ziekte van Alzheimer.
Folates
More Effective In Limiting Alzheimer's Disease Risk Than Antioxidants, Other
Nutrients
--
Adults who eat the daily recommended allowance of folates -- B-vitamin nutrients
found in oranges, legumes, leafy green vegetables and folic acid supplements --
significantly reduce their risk of developing Alzheimer's disease, according to
results from a long-term National Institute on Aging study of diet and brain
aging.
The
study also found that folates appear to have more impact on reducing Alzheimer's
risk than vitamin E, a noted antioxidant, and other nutrients considered for
their effect as a brain-aging deterrent.
Maria
Corrada and Dr. Claudia Kawas of UC Irvine's Institute for Brain Aging and
Dementia led the effort, which analyzed the diets of non-demented men and women
age 60 and older. They compared the food nutrient and supplement intake of those
who later developed Alzheimer's disease to the intake of those who did not
develop the disease. It is the largest study to date to report on the
association between folate intake and Alzheimer's risk and to analyze
antioxidants and B vitamins simultaneously.
Results
appear in the inaugural issue of the quarterly peer-reviewed research journal, Alzheimer's
& Dementia: The Journal of the Alzheimer's Association.
"Although
folates appear to be more beneficial than other nutrients, the primary message
should be that overall healthy diets seem to have an impact on limiting
Alzheimer's disease risk," said Corrada, who like Kawas started with the
study while at Johns Hopkins University in Baltimore.
The
researchers used data from the Baltimore Longitudinal Study of Aging to identify
the relationship between dietary factors and Alzheimer's disease risk. Between
1984 and 1991, study volunteers provided detailed dietary diaries, which
included supplement intake and calorie amounts, for a typical seven-day period.
Ultimately,
57 of the original 579 participants developed Alzheimer's disease. But the
researchers found that those with higher intake of folates, vitamin E and
vitamin B6 shared lower comparative rates of the disease. And when the three
vitamins were analyzed together, only folates were associated with a
significantly decreased risk.
In
turn, no association was found between vitamin C, carotenoids (such as
beta-carotene) or vitamin B-12 intake and decreased Alzheimer's risk.
"The
participants who had intakes at or above the 400-microgram recommended dietary
allowance of folates had a 55-percent reduction in risk of developing
Alzheimer's," said Corrada, an assistant professor of neurology. "But
most people who reached that level did so by taking folic acid supplements,
which suggests that many people do not get the recommended amounts of folates in
their diets."
Folates
have already been proven to reduce birth defects, and research suggests that
they are beneficial to warding off heart disease and strokes. Although folates
are abundant in foods such as liver, kidneys, yeast, fruits (like bananas and
oranges), leafy vegetables, whole-wheat bread, lima beans, eggs and milk, they
are often destroyed by cooking or processing. Because of their link to reducing
birth defects, folates have been added to grain products sold in the U.S. since
1998. But even with this supplement, it is thought that many Americans have
folate-deficient diets.
Recent
research is beginning to show relationships between folates and brain aging.
Earlier this year, Dutch scientists showed that adults who took 800 micrograms
of folic acid daily had significant improved memory test scores, giving evidence
that folates can slow cognitive decline.
"Given
the observational nature of this study, it is still possible that other
unmeasured factors also may be responsible for this reduction in risk,"
said Kawas, the Al and Trish Nichols Chair in Clinical Neuroscience. "People
with a high intake of one nutrient are likely to have a high intake of several
other nutrients and may generally have a healthy lifestyle. But further research
and clinical studies on this subject will be necessary."
Judith
Hallfrisch of the U.S. Department of Agriculture, Denis Muller with the National
Institute on Aging and Ron Brookmeyer with Johns Hopkins collaborated on the
study, which was originally undertaken at the Gerontology Research Center of the
NIA and the Department of Neurology at Johns Hopkins. Study funding came from
the Extramural Programs of the NIA.
Begun
in 1958 by the NIA, the Baltimore Longitudinal Study of Aging is America's
longest-running scientific study of human aging. BLSA scientists are learning
what happens as people age and how to sort out changes due to aging from those
due to disease or other causes. More than 1,400 men and women are study
volunteers.
(Aug. 2005)