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Epidemiologist
Martha Morris and biochemist Jacob Selhub examine graphical evidence of
the interaction between vitamin B12 status and folate status in
relation to cognitive test results.
(D935-1)
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The Age of Folate Fortification
Folate is one of the B vitamins that affect the balance
of homocysteine levels. A link between high blood folate levels and
relatively lower homocysteine levels has long been known.
Since 1998, all U.S. enriched cereal grain products,
such as bread, pasta, flour, breakfast cereal, and rice, have been
required to be fortified with folic acid—the synthetic form of
folate—to help prevent certain birth defects.
Since fortification began, not only have folate
deficiency and birth defects decreased, but so has the prevalence of
high homocysteine levels, according to Rosenberg and colleagues. High
homocysteine levels are associated with an increased risk of developing
heart disease, stroke, dementia, and Alzheimer’s disease.
“It is possible that this drop in the population’s
homocysteine concentrations may also bring about a lower incidence of
these diseases,” says Troen. “But whether this will be the case is not
yet certain. And though there are clear benefits of increasing the
population’s folic acid intake as a whole, new research suggests that
there may be a downside for some individuals.”
B Vitamins and Brain Power
Epidemiologists Paul Jacques and Martha Morris,
biochemist Jacob Selhub, and Rosenberg recently completed a study of
the interrelationships among the B vitamins and cognitive function in
this age of folate fortification. B vitamins are involved in the
synthesis of chemicals crucial to brain function. Scientists have long
known that being seriously deficient in vitamin B12 leads to impaired
cognitive function due to neurological complications. The researchers
used a combination of blood markers to classify subjects’ vitamin B12
ranking.
Morris, who led the study, found that among people aged 60 and older, those with high blood levels of folate and normal,
or adequate, vitamin B12 status scored high on cognitive function
tests. These seniors were given a test that required response speed, in
addition to attentiveness, visual-spatial skills, associative learning,
and memory.
But what about those who had low vitamin B12 blood
levels—a status that is common among seniors due to the poorer
gastrointestinal conditions that come with aging? Low vitamin B12
status was linked with lower scores on cognitive tests.
“The people with high folate and low B12 status were
more likely to exhibit both cognitive impairment and anemia than those
with normal folate and low B12 status,” says Jacques.
The researchers recommend that future studies examine
the implications of having high folate status due to fortification and
too little vitamin B12 due to aging.
What’s in a NAME?
Population researcher Katherine L. Tucker is focusing
on vitamins and cognition in a series of community-based studies. In
the Normative Aging Study, a longitudinal study of originally healthy
men in the Boston area, she and colleagues found that those with the
best B-vitamin status at the start, or baseline, had little change in
their cognitive-function test scores. But test scores went down
significantly in the men with the lowest baseline B-vitamin status and
highest homocysteine concentrations.
Rosenberg and Tucker are also working with another
high-risk group: homebound elderly. “The Nutrition, Aging, and Memory
in Elders, or NAME, study is designed to look at the relationships
among levels of several nutrients and subsequent cognitive function,”
says Tucker.
“We are studying folate, vitamin B6, vitamin B12,
vitamin C, and vitamin E intakes among this population, along with each
individual’s cognitive functioning,” she says. The data generated may
be useful in developing dietary strategies and supplementation targets
to help the elderly maintain their cognitive function.
These and future studies are essential to determining
whether—and to what extent—nutritional factors can be used to prevent
cognitive impairment as we age.—By Rosalie Marion Bliss, Agricultural Research Service Information Staff.
This research is part of Human Nutrition, an ARS national program (#107) described on the World Wide Web at www.nps.ars.usda.gov.
To reach scientists mentioned in this article, contact
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
, USDA-ARS Information Staff, 5601 Sunnyside Ave., Beltsville, MD 20705-5129; phone (301) 504-4318, fax (301) 504-1486.
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