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Folate and Choline
Interplay Investigated
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Chemist Robert Jacob prepares
blood samples for analysis in
a study of the B vitamin folate.
(K9297-1)
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Inside our bodies, the B vitamins
folate and choline work in a delicate balance. A team led by
ARS chemist Robert A. Jacob has now
shown—for the first time in healthy people—that we can't synthesize
enough choline if we are low in both choline and folate.
"That's in contrast to the assumption that the body can make as much
choline as it needs," says Jacob. He is with the ARS Western Human
Nutrition Research Center in Davis, California.
Jacob's studies with healthy men and women volunteers agree with some of the
findings of animal studies conducted earlier by ARS scientists at Tufts
University in Boston and by nutrition researchers elsewhere. In all, these
investigations helped pave the way for the recent announcement of a recommended
daily amount of choline.
"The choline recommendation," says Jacob, "is the first ever
made in the United States for this nutrient." The Food and Nutrition Board
of the National Academy of Sciences now suggests that an adequate choline
intake is 425 milligrams a day for women and 550 milligrams for men.
"There are about 250 milligrams of choline in a 12-ounce beef steak,"
he says. |
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Jacob places blood samples into a
centrifuge. The separated blood
plasma and cells will be analyzed
for substances that may be affected
by folate content in the diet.
(K9296-2)
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Choline Carries Out Many
Chores
Choline helps the body absorb and use fats, including those that become part of
membranes that keep our cells intact. "Choline deficiency," according
to Jacob, "can result in fat accumulating in the liver and subsequent
liver damage." In addition, choline is required for synthesizing
acetylcholine, a neurotransmitter needed for memory storage and muscle control,
for example.
And choline—as well as folate—contains what's known as a methyl
group, which the body uses to form genetic material, or DNA. "The process
by which methyl groups, borrowed from methyl donors such as choline and folate,
are added to DNA is known as DNA methylation," explains Jacob. It can be
monitored in blood samples and is one of several indicators of the integrity,
or condition, of DNA.
Our bodies also use methyl groups from folate and choline to convert the amino
acid homocysteine—which can be harmful at high amounts—into another
amino acid called methionine. In turn, the body can convert methionine into
S-adenosylmethionine, a valuable methyl donor. That same compound is
currently a popular supplement.
This choline- or folate-assisted conversion of homocysteine prevents the body
from accumulating an overload of homocysteine. High levels of homocysteine are
associated with increased risk of heart attack or stroke.
Choline, folate, and methionine are the body's primary sources of methyl
groups. "If your supply of folate is low," says Jacob, "your
body may compensate by taking methyl groups from choline. Our results indicate
that under those conditions, your body might not be able to synthesize enough
choline. You'll likely need more choline to help meet the increased
demand."
High Protein Means High Choline
High-protein animal products like meats and dairy foods are rich in choline. So
are soy foods. Folate is highest in plant sources such as orange juice; green
leafy vegetables like spinach; grain products fortified with this vitamin,
including bread flour, cornmeal, pasta, and rice; dried beans and peas; and
most berries. Nuts and liver contain both nutrients.
What's the best way to make sure you are getting enough folate and choline?
"As you might expect," Jacob advises, "for most healthy people,
a varied, balanced diet is probably the best bet. That should include an
assortment of plant foods, which give you folate, and animal foods, which
provide choline."
Low-Folate Regimen Leads to Choline Crunch
Jacob and colleagues conducted the folate and choline investigations in
separate studies with 11 men, aged 33 to 46, and 10 postmenopausal women, aged
49 to 63, as volunteers. All were healthy and nonsmokers. The volunteers lived
at the research center, then located in San Francisco, to ensure that they ate
only foods meticulously measured and custom prepared for them by the research
center's dietary staff. Women of childbearing age weren't allowed into the
research because of evidence associating birth defects, such as spina bifida,
with inadequate intake of folate before pregnancy.
Throughout the 13- to 15-week studies, the volunteers followed a basic regimen
that varied in the amount of folate it provided. The low-folate, low-choline
portion of the study gave them as little as 13 percent of today's recommended
daily allowance of folate, which is 400 micrograms.
Later, researchers added folate back in the form of a supplement, boosting the
level to as much as 130 percent of the recommended intake. In the men's study,
the supplement was mixed with a soybean-based, high-energy shake that the
volunteers drank at lunchtime. The women received their supplemental folate in
applesauce served at breakfast and dinner.
Tests of the volunteers' blood and liver function indicated that no severe
choline or folate deficiencies occurred during the study. Nevertheless, blood
levels of choline decreased an average of 25 to 28 percent in men and women
during the low-folate, low-choline stints. But those levels returned to at
least normal when researchers provided more folate.
"We showed that the amount of folate you get dictates how much choline you
need," Jacob says. He did the work with Donald J. Jenden of the University
of California at Los Angeles School of Medicine; Marian E. Swendseid of the
UCLA School of Public Health; and Margaret A. Allman-Farinelli of the
University of Sydney Department of Biochemistry.
The scientists published their findings in the Journal of
Nutrition.—By Marcia Wood,
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.
Robert A. Jacob is at the
USDA-ARS Western Human Nutrition Research
Center, One Shields Ave., Davis, CA 95616; phone (530) 752-4726, fax (530)
752-8502. |
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"Folate and Choline Interplay
Investigated" was published in the
March 2001
issue of Agricultural Research magazine.
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