Low levels of vitamin
B12 needed for neural tube development
Vegans, vegetarians may be at risk
Children born to women who have low blood levels of
vitamin B12 shortly before and after conception may not
have what they need to maintain a healthy neural system
development according to an analysis by researchers at
the National Institutes of Health, Trinity College
Dublin, and the Health Research Board of Ireland.
Women who consume little or no meat or animal based foods
are the most likely group of women to have low B12 levels,
along with women who have intestinal disorders that prevent
them from absorbing sufficient amounts of B12.
Researchers have known that taking another nutrient, folic
acid, during the weeks before and after conception is vital
for brain and spinal cord development.
The study appears in the March Pediatrics*. The study's
first author was Anne M. Molloy, Ph.D., Trinity College
Dublin. Scientists from the Health Research Board of Ireland
and two NIH institutes, the Eunice Kennedy Shriver National
Institute of Child Health and Human Development and the
National Human Genome Research Institute, also took part in
the study.
"Vitamin B12 is essential for the functioning of the nervous
system and for the production of red blood cells," said
Duane Alexander, M.D., director of the NICHD.
The study authors wrote that it is not known how B12 and
folate might interact to influence the formation of the
neural tube, the embryonic structure that gives rise to the
spine and brain. They noted that the two vitamins are
jointly involved with several key biochemical reactions, as
well as with the synthesis of DNA. Lack of either Vitamin
B12 or folate in any of these chemical processes
theoretically could affect development of the neural tube .
The authors suggested, that women should have Vitamin B12
levels above 300 ng/L before becoming pregnant. (Because B12
levels drop sharply during pregnancy, the researchers
adjusted the levels measured during pregnancy to provide a
target level for women to achieve before they become
pregnant.)
Because Vitamin B12 comes from foods of animal origin, women
who adhere to a strict vegan diet may be at risk for a B12
deficiency, said an NICHD author of the paper, James L.
Mills, M.D., senior investigator in the Division of
Epidemiology, Statistics, and Prevention Research. He added
it is advisable for women with digestive disorders that
interfere with the absorption of foods to consult a
physician before getting pregnant, to make sure they are
receiving adequate amounts of B12.
Dr. Mills explained that critical events in the formation of
the brain and spinal column occur very early in pregnancy—in
the first 28 days after conception—before many women even
realize they are pregnant.
He added that the U.S. Public Health Service recommends that
all women of childbearing age consume 400 micrograms of
folic acid each day. This amount assures that a woman will
have adequate stores of the vitamin, in the event of an
unintended pregnancy.
Similarly, he said, it would be wise for all women of
childbearing age to consume the recommended amount of
Vitamin B12, whether they are planning a pregnancy or not.
"Half of the women who become pregnant each year in the U.S.
were not planning to become pregnant."
*Anne M. Molloy et al. Pediatrics 2009; 123: 917-923.
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