| Folic Acid
Folic acid is a B vitamin needed for cell replication
and growth. Folic acid helps form building blocks of DNA, the body’s
genetic information.
What does it do? Folic acid is a B vitamin
needed for cell replication and growth. Folic acid helps form building
blocks of DNA, the body’s genetic information, and building blocks
of RNA, needed for protein synthesis in all cells. Therefore, rapidly
growing tissues, such as those of a fetus, and rapidly regenerating
cells, like red blood cells and immune cells, have a high need for
folic acid. Folic acid deficiency results in a form of anemia that
responds quickly to folic acid supplementation.
The requirement for folic acid increases considerably during pregnancy.1
Deficiencies of folic acid during pregnancy are associated with
low birth weight and an increased incidence of neural tube defects
in infants.2 In one study, women who were at high risk
of giving birth to babies with neural tube defects were able to
lower their risk by 72% by taking folic acid supplements prior to
and during pregnancy.3 Most doctors, many other healthcare
professionals, and the March of Dimes recommend that all women of
childbearing age supplement with 400 mcg per day of folic acid.
Such supplementation would protect against the formation of neural
tube defects during the time between conception and when pregnancy
is discovered. If a woman waits until after pregnancy has been discovered
to begin taking folic acid supplements, it will probably be too
late to prevent a neural tube defect.
Other birth defects may be prevented with folic acid supplementation
as well. Women who take folic acid–containing multivitamin supplements
around the time they conceive may also reduce the risk of other
congenital malformations, such as heart defects, defects of the
upper lip and mouth,4 urinary tract defects,5
6 and limb-reduction defects.7 8
Rates of prevention of cleft lip and cleft palate may be improved
by using very large amounts of folic acid (6 mg per day).9
A doctor should supervise anyone wishing to take this much folic
acid.
Folic acid is needed to keep homocysteine (an amino acid by-product)
levels in blood from rising. A growing body of evidence suggests
that an elevated homocysteine level is a risk factor for heart disease
10 and may also be linked to several other diseases.
Folic acid and certain other B vitamins function as cofactors for
enzymes that can lower homocysteine levels. Research has shown that
supplementing with folic acid reduces homocysteine levels.11
Of the B vitamins with a role in homocysteine metabolism, folic
acid appears to be the most important in lowering homocysteine levels
for the average person.12 13 A deficiency
of folic acid has also been associated with peripheral vascular
disease and coronary artery disease even in people with normal homocysteine
levels, suggesting that the vitamin may have protective effects
that extend beyond its role in maintaining normal homocysteine levels.14
In 1996, the FDA began to require that all enriched flour,
rice, pasta, cornmeal, and other grain products contain 140 mcg
of folic acid per 100 grams.15 Among people who do not
take vitamin supplements, this amount of food fortification has
been associated with increased folic acid levels in the blood and
decreased blood levels of homocysteine.16 Nevertheless,
evidence is mounting that the FDA-mandated level of folic acid fortification
in food is inadequate to fully prevent neural tube defects.17
Until fortification rates are quadrupled, women who can possibly
become pregnant are advised to take a folic acid supplement of 400
mcg per day.
A diet low in folic acid has been associated with a high incidence
of pre-cancerous polyps in the colon, suggesting that folic acid
may prevent the development of colon cancer.18 Two studies
have shown that reduced folic acid levels are associated with an
increase in the incidence of cancer in people with ulcerative colitis
19 20 and a third study showed the degree
of abnormal cell growth decreases as folic acid intake increases.21
Three large population studies showed that low folic acid intake
is associated with an increased risk of colorectal cancer.22
23 24
In addition, decreased blood levels of folic acid are associated
with an increased risk of colon cancer in women.25 Long-term
supplementation with folic acid from a multivitamin has been found
in one large population study to be associated with a reduced risk
of colon cancer. However, 15 years of supplementation was necessary
before a significant reduction in colon-cancer risk became apparent.
In that study, folic acid from dietary sources alone was associated
with a modest reduction in the risk of colon cancer.26
Total folic acid intake was not associated with overall risk
of breast cancer in preliminary studies.27 28
However, among women who consume at least one alcoholic beverage
per day, the risk of breast cancer appears to be highest among those
with low folic acid intake. Current use of a multivitamin supplement
has also been associated with lower breast cancer risk among women
who consume at least 1.5 alcoholic beverages per day, compared to
those who never use a multivitamin supplement.
Where is it found? Beans, leafy green vegetables,
citrus fruits, beets, wheat germ, and meat are good sources of folic
acid.
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