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Can vitamins prevent birth defects?

It is 28 days since sperm met egg. Their meeting may still be unsuspected. Already the tube that should eventually become the new human's spinal cord and brain is forming. But the seam of this "neural" tube fails to close.

The embryo continues to grow into a fetus, but the early error is Costly. If the open seam occurs at the top of the tube, the brain never develops. Babies born with this condition-known as anencephaly-die within a few hours of birth.

if the opening occurs in the spine, the baby is born with a portion of the spinal cord exposed or, less commonly, covered only with skin. Two-thirds of these children survive into childhood. But the birth defect, known as spina bifida, takes its toll.

An exposed spinal cord is easily damaged. Often, the children lack bladder or

bowel control, many are paralyzed below the waist, and some accumulate excess fluid in their brains, which can lead to mental retardation.

Can anything prevent these tragedies? Doctors can usually detect the defects by measuring the levels of a protein (alphafetoprotein) in the mother's blood or in fluid from the sac that envelops the fetus. That gives the mother the difficult choice of whether to have an abortion during the second trimester of pregnancy.

But a new study offers a better solution: It provides compelling evidence that vitamins may actually reduce the risk that the errors will occur in the first place.1

"Our study indicates that by taking multi-vitamins containing at least 100 micrograms of folic acid during the first six weeks of pregnancy, women can reduce the risk of neural-tube defects [NTDS] by 50 to 70 percent:' says primary author Aubrey Milunsky, of Boston University School of Medicine.

Despite this news, the Centers for Disease Control (CDC), the National Institutes of Health, and the American College of Obstetrics and Gynecology still refuse to recommend that women start taking vitamins with folic acid before they become pregnant. (By the time women know they're pregnant, it may be too late.)

Ironically, the National Academy of Sciences recently halved the Recommended Dietary Allowance for folic acid for pregnant and non-pregnant women. its new RDA book doesn't discuss NTDS at all.

A TERRIBLE TOLL

Roughly one of every 1,000 babies born in the U.S. has a neural-tube defect. That makes it the second most common birth defect, after Down syndrome.

In part because women can now choose to abort a fetus with an NTD, the number of children born with spina bifida declined by 17 percent between 1980 and 1987. Nevertheless, the CDC estimates that medical and surgical care for all children with the birth defect costs $200 million per year.1

The cost per child-which includes multiple operations to improve the chances of walking and to drain fluid from the brain, disability payments, wheelchairs, leg braces, special education, and loss of parents' income is estimated at $250,000. more difficult to measure.

FINGERING FOLIC ACID

The idea that vitamins can prevent NTDS "has been around a long time," says Joseph Mulinare, of the CDC. In particular, researchers have guessed that folic acid, a B-vitamin found in some leafy greens, beans, peas, yeast, and other foods, may play a role. Here's why: n A drug that prevents the body from using folic acid (aminopterin) causes NTDS in mice, cats, and rats.

* Women who had babies with NTDS ate folic-acid-poor diets and had low levels of folic acid in their blood.

* Among British women who had already delivered one child with an NTD, those who took folic-acid-containing multi-vitamin supplements were less likely to have another affected baby.

But none of this evidence was conclusive. For example, the British studies were flawed because hospital ethics committees refused to let the researchers randomly assign some mothers to the "no-supplement" group. There was too much evidence, said the committees, to not give supplements to NTD-mothers. Talk about Catch 22.

INCONCLUSIVE CASE-CONTROLS

Since then, the British Medical Research council has decided that a randomized trial is indeed ethical. But the results may not be in for years, because it's so hard to find participants-women who already have had a child with an NTD who are not already taking vitamins and who are willing to take a 50-50 chance of ending up in the "no-supplement" placebo group. A second study is underway in Hungary, and the CDC would like to start one in China, which has the world's highest incidence of spina bifida.

* In the meantime, researchers have completed four less-rigorous studies:

* J. Mills and colleagues at the National institute for Child Health and Human Development did a similar case-control" study, but found no link between vitamins and NTDs. However, their ambiguous questionnaire may have obscured a link.

* In two separate studies, the CDC'S Mulinare and researchers at the University of Western Australia found that mothers of babies with NTDS reported consuming less folic acid around the time of conception than mothers of babies without NTDS.

* Boston University's Milunsky found that the prevalence of NTDS was about 70 percent lower among women who took folic-acid-containing multi-vitamins during the first six weeks of pregnancy than among women in three groups: those who took no vitamins during pregnancy, those who took vitamins without folic acid during the first six weeks, and those who took multi-vitamins with folic acid, but only after the first six weeks of pregnancy)

"Based not just on this study, but on the huge body of information we've accumulated on multi-vitamins and NTDS," says Milunsky, "I believe we have a rational basis to recommend multi-vitamin supplements containing folic acid during that critical period of pregnancy'"

But others are not so bold, if recommending a safe vitamin supplement can be called bold.

CAUTION REIGNS

"To make a public-health recommendation for 8 to 10 million women all women at risk of pregnancy-we need more consensus," says the CDC'S Mulinare. "We don't want to be in a position where vitamins are being touted as a miracle drug before we've resolved some remaining inconsistencies.'

(Indeed, it would be unfortunate if claims about birth defects appeared on folic-acid supplements before the FDA adopts a general policy regulating health claims on labels.)

But it's not just the fear of being wrong that makes researchers balk at recommending folic acid supplements. "We know that [excess] vitamin A can cause birth defects," says Mulinare. "Other vitamins may also increase the risk."

He adds, however, that vitamin A aside, no studies have shown a harmful effect of supplements in humans. "There doesn't appear to be any downside to taking folic acid in normal doses:' says Milunsky, "as long as people realize that more is not better."

It's puzzling that some researchers are worried about the dangers of multivitamin supplements. After all, doctors routinely prescribe them at the first prenatal appointment, whether that's in the second week or the twelfth. The problem is: for most women, the first appointment comes too late.

"Even your best obstetricians see patients 8 to 10 weeks after conception:' notes Milunsky. "That's absurd. Prenatal care is beginning after fetal development is completed."

And so the researchers await the results of more studies. In the meantime, sperms continue to meet eggs, and errors continue to be made. And some of them might have been preventable.

Our Advice

All women who could become pregnant should take a multivitamin supplement that contains 400 micrograms of folic acid, or should examine their diets to make sure they get at least 400 mcg per day from food. That's 100 percent of the U.S.RDA for non-pregnant women.

Once a pregnancy is diagnosed, switch to a prenatal supplement that contains 800 mcg. To play it safe, do not take high-dose multi-vitamins, especially those that contain more than 8,000 IU of vitamin A in the form of retinol.
 Where to Get Folic Acid
 Food Folic Acid
 (1 cup, unless specified) (mcg)
 Liver, chicken, cooked (3 oz.) 655
 Lentils, cooked 358
 Brewer's yeast (1 Tb.) 313
 Pinto beans, cooked 294
 Spinach, cooked 262
 Red kidney beans, cooked 229
 Asparagus, cooked 176
 Turnip greens, cooked 171
 Chick-peas, canned 160
 Lima beans, mature, cooked 156
 Broccoli, cooked (1 spear) 123
 Split peas, canned 123
 Orange juice, frozen 109
 Spinach, raw 109
 Brussels sprouts, cooked 94
 Peas, frozen, boiled 94
 Beets, cooked 90
 Wheat germ, toasted (1 oz.) 80
 Romaine lettuce, raw 76
 Cauliflower, cooked 63
 Source: USDA
COPYRIGHT 1990 Center for Science in the Public Interest
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1990, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

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Title Annotation:neural-tube defects
Author:Liebman, Bonnie
Publication:Nutrition Action Healthletter
Date:Jan 1, 1990
Words:1398
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