Folic acid's trade-offs of concern

January 27, 2008|By Stephanie Desmon | Stephanie Desmon,Sun reporter

It was all about the babies. A decade ago, when the U.S. required flour, bread and pasta to be fortified with folic acid, health experts believed it would help prevent devastating birth defects such as spina bifida.

There's no question that it worked. As many as 1,000 newborns a year in the United States - and many more elsewhere - have been spared so-called neural tube defects because their mothers got a crucial infusion of folic acid before they even knew they were pregnant.

But now some scientists are asking whether there have been unforeseen trade-offs for the population as a whole - including thousands of additional colon cancer cases each year, a somewhat smaller bump-up in prostate cancer, and an increase in cognitive impairment among the elderly.

"The existing science at the time this decision was made showed the benefits and not any significant risk," said Dr. Joel Mason, director of the Vitamins and Carcinogenesis Laboratory at the U.S. Department of Agriculture's Human Nutrition Research Center at Tufts University. "What has evolved is, there's an increasing level of concern that it might be harming some segments of the population."

The renewed debate comes at a time when activists in the United States are pushing to increase the amount of folic acid in fortified foods, under the theory that if some is good, then more is better.

It also comes as the United Kingdom has put on hold its effort to require folic acid fortification. Scientists there are considering new research suggesting a possible downside to adding folic acid to the national diet.

Not everyone is convinced there even is a debate. The benefits of folic acid have been clearly proved, they say, and if anything, women of childbearing age need more folic acid than fortified foods provide. Proponents say that in addition to deterring birth defects, folic acid might prevent some cancers, strokes and cardiovascular disease.

And any potential downsides, they argue, are unproven.

Dr. Walter Willett, chairman of the department of nutrition at the Harvard School of Public Health, said time will show that there are more benefits to folic acid than previously known - and not that it causes cancer.

Though scientists don't fully understand how folic acid works, they believe that it assists in the formation of the building blocks of DNA, stimulating cell growth, preventing damage and helping DNA to replicate.

In normal tissue, it helps cells to divide and grow and proliferate. In cells where cancer is just beginning, folic acid is believed to have the same effect - causing fast-growing cancer cells to reproduce even more rapidly.

Chemically, folic acid is the synthetic form of folate, a member of the vitamin B family. Green leafy vegetables, dried beans and nuts are among the foods naturally rich in folate. But before flour-based products were fortified, dietary supplements were among the only ways that women of child-bearing age could ensure an intake of 400 micrograms a day - the dosage believed to prevent birth defects.

Not enough women did it on their own, which is why the U.S. turned to fortification. Today, some breakfast cereals alone contain 400 micrograms of folic acid per serving. Even so, the March of Dimes, a national advocacy group devoted to reducing birth defects, is considering petitioning the Food and Drug Administration to increase the amount of folic acid required in fortified foods.

The concept of fortification isn't new. One of the earliest successful efforts was the addition of iodine to salt in 1924 to prevent goiter and other symptoms of severe iodine deficiency.

Vitamin D was first added to milk in the 1930s to prevent rickets. When folic acid in flour and bread became mandatory in 1998, those staples had long been fortified with thiamin, niacin and riboflavin.

Dr. Frank Witter, a professor of gynecology and obstetrics at Johns Hopkins, said fortification isn't enough by itself. Some women still don't get the necessary folic acid. But he would not advocate an increase in fortification levels.

"We have to strike a balance," he said. "Even water, there's a downside for too much and a downside for too little. The fortification is probably at an adequate level. [But] you can't really count on any fortification process to completely correct a problem."

A study published last summer by Tufts' Mason and his colleagues suggested a possible link between folic acid fortification and U.S. and Canadian colorectal cancer rates, which are no longer declining as quickly as they once were.

Since the introduction of mandatory folic acid fortification in those two countries, an expected drop in colon cancer rates has shown an uptick, translating to as many as 15,000 extra cases of colon cancer in the U.S. annually and 1,500 in Canada - cases that researchers say might not have occurred without folic acid.

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