Finding the Folate in Foods
Leafy greens, dried beans
and peas, fortified cereals
and grain products, and some
fruits and vegetables are
rich sources of folate.
Nutrition scientists need sophisticated technologies to
distinguish quantities of key nutrients in foods. Indeed, sound nutritional
advice is based on good food analysis. Now, Agricultural
Research Service scientists at the Food Composition Laboratory (FCL),
in Beltsville, Maryland, have developed a new method to analyze the
essential B vitamin folate in foods and in blood serum.
Folate piqued America's nutritional interest when the
Food and Drug Administration in 1998 required that grain products be
fortified with it. Evidence showed that risks of birth defects would
drop if mothers-to-be took more folic acid.
Folate is important to white blood cell makeup and for
regulation of the amino acid homocysteine. Folate is also involved in
nucleic acid synthesis and methylation reactions, both of which help
the body form genetic material, or DNA.
"Dietary folate is important for all aspects of lifeespecially
during growth," says Robert J. Pawlosky, the FCL chemist who first
reported the new folate analysis method last year. "It also appears
to be important for maintaining cardiovascular tone and preventing heart
Folate is a generic term used for a family of related
compounds that exhibit similar vitamin activity within the body. The
family includes folic acid, which is the major synthetic form of folate
used by food processors to fortify foods. Each is absorbed by the body
at different rates.
The new method for analyzing the amount of folate in foods
uses high-performance liquid chromatography and mass spectrometry, or
HPLC-MS. Current methods do not test for individual folates separately.
But, says Pawlosky, "With the combination of HPLC-MS and stable
isotopes, we can detect and measure very low levels of specific folates."
The lab is now perfecting yet another way to analyze folateHPLC
with fluorescence detection. It's a less expensive method, but one that
will complement the HPLC-MS method.
Accuracy is important to experts who establish and reexamine
the nationally recommended folate levels and who monitor the folate
fortification program. For example, in 1989, the recommended dietary
allowance was lowered from 400 micrograms (mcg) to 200 mcg for men and
180 mcg for women. Then, in 1998, dietary folate equivalents were establishedbecause
of differences in bioavailability, or absorptionof at least 400
mcg per day for adults.
The ARS researchers now have a memorandum of understanding
with the Nutrition Institute at the University of Chile at Santiago.
Together, they are testing food and blood samples to gauge levels of
folate and folic acid. Chile's program is designed to compare the country's
fortification program of foods with how much they find in the Chilean
population. Pawlosky says lessons from the program's design may eventually
be used as a model for similar programs in the United States.
FCL scientists are also working with the National Institute
of Standards and Technology (NIST) and the Centers for Disease Control
and Prevention (CDC) to coordinate their assays of folate status in
blood. The CDC monitors nutrition status across the country, and NIST
develops assays for private technicians to use commercially in clinical
labs.By Rosalie Marion Bliss,
Agricultural Research Service Information Staff.
This research is part of Human Nutrition, an ARS National
Program (#107) described on the World Wide Web at http://www.nps.ars.usda.gov.
"Finding the Folate in Foods" was published in the December 2002 issue of Agricultural Research magazine.