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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.

SUPPLEMENTS' FRINGE BENEFIT

Postmenopausal women who take calcium and vitamin D supplements to protect their bones appear to reap an added benefit - less weight gain.

As a general rule, women pack on about five additional pounds (2.3 kilograms) as they pass through menopause. Their weight tends to stabilize in their 60s and they actually lose pounds (mostly muscle mass) in their 70s.

However, a new study involving more than 36,000 women aged between 50 and 79 found that those who took calcium and vitamin D gained less weight than those who didn't take the supplements. At the end of the seven-year study, those on supplements weighed an average of 0.28 pounds less than women in the other group, according to the study published in the Archives of Internal Medicine.

"It's not a huge difference, but you might as well take every bit [of weight loss] you can get," said the lead researcher, Bette Caan at Kaiser Permanente in Oakland, Calif. She speculated that the supplements stimulate the breakdown of fat cells and reduce the absorption of fat by the intestines.

KETCHUP'S FALL FROM GRACE

Bad news for ketchup lovers: The popular condiment has apparently lost its status as a cancer fighter.

Ketchup suddenly gained the reputation as a "health food" a few years ago, when several small studies indicated that lycopene - an antioxidant found in tomatoes - reduces men's risk of prostate cancer.

In fact, ketchup and tomato sauce are better sources of lycopene than fresh tomatoes. Both products are a concentrated form of tomatoes, and the way they are processed makes it easier for the intestines to absorb the lycopene in the tomatoes.

But a new and extensive study, published in the journal Cancer Epidemiology Biomarkers & Prevention, found that lycopene "does not effectively prevent prostate cancer."

The researchers came to this conclusion after examining blood levels of lycopene from more than 28,000 men enrolled in a cancer screening trial sponsored by the U.S. National Cancer Institute.

"It is disappointing, since lycopene might have offered a simple and inexpensive way to lower prostate-cancer risk for men concerned about this common disease," Ulrike Peters, the lead researcher from the Fred Hutchinson Cancer Research Centre in Seattle, said in a statement released with the study.

"Unfortunately, this easy answer just does not work."

ptaylor@globeandmail.com