Pregnant women with low levels of vitamin B12 are at a heightened risk of having a child with a serious birth defect, according to Canadian researchers.
For their study, led by Joel Ray of St. Michael's Hospital in Toronto, the researchers examined blood samples from a large group of pregnant women. The findings, published in the journal Epidemiology, revealed that women with the lowest levels of vitamin B12 had three times the risk of delivering babies with neural tube defects such as spina bifida, in which the spine is severely deformed.
The main dietary sources of B12 are fish, meat, dairy products and eggs.
Dr. Ray noted that "pure vegetarians who do not consume animal products" run the risk of becoming vitamin-B12 deficient. As well, a small minority of women do not properly absorb the vitamin from their food.
Although most people get adequate amounts of the vitamin, the new study suggests that pregnant women possibly need "higher than normal levels" to reduce the chances of birth defects.
The researchers urged policy makers to consider vitamin B12 "fortification" of commonly eaten foods - as was done with folic acid.
Canadian food manufacturers are required by law to add folic acid to white flour, pasta and cornmeal. Since that policy took effect in 1998, the rate of neural tube defects has fallen by almost 50 per cent and now stands at one in every 1,000 pregnancies.
Folic acid, which is also a B vitamin, is essential to healthy fetal development in the weeks after conception - a time when a woman might not yet realize she is pregnant.
Dr. Ray said that adding B12 to some foods could ensure that pregnant women have sufficient levels of this vitamin when they need it most.
In the meantime, women of childbearing age, especially vegetarians, should take a daily supplement containing between 10 and 50 micrograms of B12, he said.
