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USA Health System
News Release
Mobile, Ala. (September 2, 2009)
Contact: Ashley Gruner, (251) 470-1682

USA Folate Researchers Uncover The Limitations of a Very Good Thing

A recent study by Drs. Steven W. Bailey and June E. Ayling, both researchers in the department of pharmacology at the University of South Alabama College of Medicine, found that despite well-known health benefits of folic acid, supplementation with this vitamin may have no additional benefit when taken in excess.

Based primarily on the reduction of neural tube birth defects that folic acid provides when taken before conception, the United States and other countries supply their entire population by enriching bread and flour with the compound. In addition to the prevention of birth defects, it is commonly used to treat anemia. It may also play a role in controlling certain forms of depression and may decrease the risk for stroke and dementia.


Folic acid, however, is a synthetic form of the vitamin that is not present in significant amounts in fresh natural foods. Instead, all functions of this vitamin are performed by naturally occurring folates called tetrahydrofolates. Until folic acid is converted into these active forms it can serve no biological purpose.


In their study, which was published in last week’s Proceedings of the National Academy of Sciences, Drs. Bailey and Ayling measured the ability of human livers to activate folic acid in comparison to livers from rats. They discovered that the average rate of folic acid activation in the human liver was 56 times lower and more variable than in rat livers.


“What we found is that humans have difficulty metabolizing amounts of folic acid that are greater than the Reference Daily Intake,” said Dr. Bailey.


Dr. Bailey is quick to emphasize that there are important health benefits of folic acid supplementation and says there is every reason for women of child-bearing age to continue taking folic acid.


“The take-home message of our work is that while folic acid is an effective nutritional supplement for preventing and treating some diseases, there may be no benefit to consuming more than the recommended amount,” he said.


The researchers point to the fact that the human liver has only a limited amount of the enzyme needed to convert folic acid to active folate, the metabolite that is directly associated with health benefits. As a result, not only does any excess go to waste, but there is speculation that residual unmetabolized folic acid may exacerbate several conditions such as cancer.


Found naturally in many fruits and vegetables - romaine lettuce, spinach, asparagus, broccoli and oranges - as well as liver, folate is often supplied instead through vitamin supplements and fortified foods that incorporate synthetic folic acid.


The U.S. Reference Daily Intake set by the Food and Drug Administration is 0.4 milligrams for adults and 0.8 milligrams for pregnant women. However, people often consume more than the recommended amounts, with fortified breakfast cereals alone providing up to 0.8 milligrams per standard serving size. According to the new research, consuming both a highly fortified breakfast cereal and a multivitamin supplement can exceed the human capacity to quickly activate synthetic folic acid.

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Date last changed: September 2, 2009 10:26 AM