Folic Acid Does Reduce Birth Defects: Another Study

This
is not really news, I guess, but it is a good reminder.
 In fact I've written about
it twice before ( href="http://scienceblogs.com/corpuscallosum/2006/10/folate_supplementation_america.php">1 href="http://scienceblogs.com/corpuscallosum/2007/01/reversal_of_progress_on_folate.php">2).
 The first post showed evidence that Americans still are not
getting enough folic acid in their diets.  The second showed
there actually has been a loss of progress in the effort to make sure
that women of childbearing potential get enough of the nutrient.



This most recent study pertains to Canada.  It shows that
Canada also has been making progress.  Moreover, it shows a
corresponding decrease in the incidence of href="http://www.nlm.nih.gov/medlineplus/neuraltubedefects.html">neural
tube defects after grain product supplementation was instituted.  

From the Canadian news:

face="Helvetica, Arial, sans-serif"> href="http://www.ctv.ca/servlet/ArticleNews/story/CTVNews/20070712/folic_acid_070712/20070712?hub=Health">Folic
acid fortification cut birth defect rates

Thu. Jul. 12 2007

CTV.ca News Staff



In the 10 years since Canadian food manufacturers began fortifying
their grain-based products with folic acid, the rate of spina bifida
and other neural tube birth defects has been cut in half, a new study
reveals.

The news reports are based upon a study published in the New
England Journal of Medicine:

href="http://content.nejm.org.proxy.lib.umich.edu/cgi/content/short/357/2/135">

Reduction in Neural-Tube Defects after Folic Acid Fortification in
Canada

Philippe De Wals, et. al.

Volume 357:135-142; July 12, 2007; Number 2

face="Helvetica, Arial, sans-serif">Background
In 1998, folic acid
fortification of a large variety of cereal products became mandatory in
Canada, a country where the prevalence of neural-tube defects was
historically higher in the eastern provinces than in the western
provinces. We assessed changes in the prevalence of neural-tube defects
in Canada before and after food fortification with folic acid was
implemented.



Methods The study population included live births,
stillbirths, and terminations of pregnancies because of fetal anomalies
among women residing in seven Canadian provinces from 1993 to 2002. On
the basis of published results of testing of red-cell folate levels,
the study period was divided into prefortification,
partial-fortification, and full-fortification periods. We evaluated the
relationship between baseline rates of neural-tube defects in each
province and the magnitude of the decrease after fortification was
implemented.



Results A total of 2446 subjects with neural-tube
defects were recorded among 1.9 million births. The prevalence of
neural-tube defects decreased from 1.58 per 1000 births before
fortification to 0.86 per 1000 births during the full-fortification
period, a 46% reduction (95% confidence interval, 40 to 51). The
magnitude of the decrease was proportional to the prefortification
baseline rate in each province, and geographical differences almost
disappeared after fortification began. The observed reduction in rate
was greater for spina bifida (a decrease of 53%) than for anencephaly
and encephalocele (decreases of 38% and 31%, respectively).



Conclusions Food fortification with folic acid was
associated with a significant reduction in the rate of neural-tube
defects in Canada. The decrease was greatest in areas in which the
baseline rate was high.

This is another instance of a very inexpensive intervention that makes
huge difference.  



More specifically, the supplementation began in 1997.  In 1998
there were detectable improvements in blood samples drawn from the
general population.  The improvements plateaued in 1999.
 Unfortunately, the study does not extend to the present time,
so we do not know if Canadians have started to show a reversal of
progress, as has been demonstrated in the United States.



Neural tube defects are not the only problems associated with low
folate
during gestation ( href="http://www.ajcn.org/cgi/content/full/71/5/1295S">Folic
acid: influence on the outcome of pregnancy):

face="Helvetica, Arial, sans-serif">During
pregnancy, low concentrations of dietary and circulating folate are
associated with increased risks of preterm delivery, infant low birth
weight, and fetal growth retardation. A metabolic effect of folate
deficiency is an elevation of blood homocysteine. Likewise, the
presence of maternal homocysteine concentrations have been associated
both with increased habitual spontaneous abortion and pregnancy
complications (eg, placental abruption and preeclampsia), which
increase the risk of poor pregnancy outcome and of decreased birth
weight and gestation duration.

Currently, it is standard practice to start women on prenatal vitamins
when it is know they are pregnant.  But the time of greatest
vulnerability is when during the first few weeks of pregnancy, at a
time when the pregnancy likely has not been detected yet.
 Therefore, the best recommendation is for women with
childbearing potential to take a decent multivitamin on a daily basis.
 Note the the href="http://www.cfsan.fda.gov/%7Elrd/fr96305c.html">current
FDA recommendation is to not exceed 1,000 micrograms of folate
(1 milligram) per day.  Also note that, in their ruling, they
noted that the evidence establishing a safe upper limit is not solid.
 Part of the concern is that higher levels can mask the
precence of a deficiency of vitamin B₁₂,
as is seen in href="http://www.merck.com/mmpe/sec01/ch004/ch004i.html#sec01-ch004-ch004j-379">pernicious
anemia, among other conditions.  (This is
particularly important for href="http://www.vegansociety.com/html/food/nutrition/b12/">people
who eat only plants.)



So, as I mentioned, this is not really news.  The salutary
effects of folic acid during gestation were well established prior to
the Canadian study.  Still, it is good to see a study that
provides evidence of improved clinical outcomes, and it is a good
reminder of a critical piece of public health information.