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Folic acid may mask vitamin deficiency

For older people, consuming high amounts may curb anemia, a key sign of a B-12 shortage.

August 04, 2003|Shari Roan | Times Staff Writer

For the past five years, folic acid has been added to cereal and grain products in the United States in an effort to reduce neural tube birth defects, deformities in which the spinal cord is exposed in a developing fetus.

Since then the fortification has been credited with reducing these defects by 20%. But the addition may be causing an unintended problem for people at the other end of the age spectrum.

The extra folic acid may be masking vitamin B-12 deficiency in people 60 and older, warns one of the nation's leading researchers on the B vitamins.

Folic acid and vitamin B-12 are needed to produce sufficient numbers of normal red blood cells, and a shortage of either can cause anemia. Too little B-12 can also cause such neurological problems as dementia.

Consuming a high amount of folic acid can eliminate the anemia and its symptoms, leaving individuals and their doctors without the most obvious sign of too little B-12. But an individual can continue to suffer from less noticeable neurological deterioration, Dr. Ralph Green, chairman of the department of pathology at the UC Davis Health System said in a presentation last month at the annual meeting of the American Assn. for Clinical Chemistry in Philadelphia.

Most often, a B-12 deficiency is only recognized when a patient complains about fatigue, a classic symptom of anemia, said Green. "My concern is that there is now less reason for elderly people with B-12 deficiency to seek medical treatment; they won't have immediate symptoms associated with anemia."

An estimated 15% of people 60 and older have some degree of vitamin B-12 deficiency. Aging can reduce the body's ability to absorb vitamin B-12, as can digestive disorders and medications that block stomach acid, also more common among older people. Vegetarians are also more likely to be deficient.

Over time, a vitamin B-12 deficiency can cause a deterioration of the brain and nervous system, leading to dementia and even paralysis. In addition, recent evidence strongly suggests that too little B-12 can lead to high levels of homocysteine in the blood. People with high levels of homocysteine, an amino acid, are at a greater risk for heart disease. Green recently presented data from the Sacramento Area Latino Study on Aging that showed a link between B-12 deficiency and increased homocysteine.

There is no evidence, so far, that folic acid fortification is causing more cases of undiagnosed vitamin B-12 deficiency, Green said. But previous studies have shown that folic acid doses of more than 1 milligram per day can lead to undiagnosed cases of B-12 deficiency. The U.S. government advises people to avoid consuming more than 1 milligram of folic acid per day.

"There is no question that large doses of folic acid [masks B-12 deficiency]. The question is, could it happen with lower doses of folic acid. That is unclear," Green said.

More surveillance of possible B-12 deficiency and additional studies are needed, said Dr. Irwin Rosenberg, dean of the Gerald J. and Dorothy R. Friedman School of Nutrition Science and Policy at Tufts University.

"There are strong arguments being made to increase the amount of folic acid in the food supply to decrease neural tube defects," he said. "That would put more people over the upper limit. This is in spite of the fact that we haven't explored the effectiveness or risk adequately."

Green recommends that elderly people be tested for vitamin B-12 deficiency on a yearly basis. Improved diagnostic tests for B-12 deficiency could make such screening feasible. "Right now, none of the screening tests is ideal," he said.

Short of routine B-12 testing, Green suggests that people age 60 and older avoid excessive folic acid. The vitamin is also found in dark green, leafy vegetables; citrus fruits; and beans. A typical folic acid supplement contains 0.4 milligrams.

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