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Other common name(s):
folate, folacin, vitamin B9
Scientific/medical name(s):
pteroylglutamic acid
Description
Folic acid (folate) is a B vitamin found in many vegetables,
beans, fruits, whole grains, and in fortified breakfast cereals (see Vitamin
B Complex). It helps the body build and maintain
DNA and is important in helping the body make new cells, especially red
blood cells.
Overview
Low blood levels of folic acid have been linked with higher
rates of colorectal cancer and some other cancers, as wells as with
certain birth defects. It is not clear whether consuming high amounts
of folic acid (from the diet or from supplements) can lower cancer risk
in average people, or how much folic acid might be needed to be
helpful. Studies looking at these issues are now under way. High doses
of folic acid can interfere with the effectiveness some chemotherapy
drugs, such as methotrexate.
How is it promoted for use?
Folic acid (folate) is a B vitamin promoted mainly as part of
a healthy diet to reduce the risk of neural tube birth defects (such as
spina bifida and anencephaly), some types of cancer, and heart disease.
It has also been studied for use in Alzheimer's disease and in chronic
fatigue syndrome. While evidence of its ability to reduce neural tube
defects in infants (when taken by the mother before and during
pregnancy) is fairly strong, its effects against other conditions are
still under study.
What does it involve?
The terms "folate" and "folic acid" are often used
interchangeably, although they are slightly different. Folate is a
naturally occurring vitamin found in dark leafy green vegetables,
citrus fruits, liver, and in smaller amounts in many other foods
(broccoli, beans, peas, eggs, etc.). "Folic acid" is a man-made form of
this vitamin, and is actually easier for the body to absorb and use.
Folic acid is found in fortified grain-based cereals and breads, and
supplements are available in tablet and powder form in drug stores and
health food stores. Most multivitamins contain folic acid.
In the United States, the current recommended dietary
allowance (RDA) is 400 micrograms (mcg or µg) per day for adolescents
and adults, and 600 mcg per day for pregnant women.
What is the history behind it?
Folic acid was first identified in the 1930s as a substance
that helped prevent anemia (low red blood cell levels) during
pregnancy. It is named after the Latin word for leaf (folium), because
it was first isolated from spinach and other green leafy vegetables.
The first studies that looked at the connection between folic
acid and cancer took place in the 1960s and 1970s. Researchers noted
that cells from the cervix in folate-deficient women looked similar to
cervix cells showing early signs of cancer and began to suspect a link
between the two. By the 1990s, population-based studies found that
certain cancers, such as cervical and colorectal cancer, were more
likely to develop in people with lower blood levels of folic acid.
The importance of folic acid in preventing neural tube birth
defects led the Food and Drug Administration (FDA) to require that
grain-based foods, cereals, and dietary supplements be enriched with
folate starting in 1998. Neural tube defects are a type of birth defect
that occurs early in fetal development, when part of the brain or
spinal cord does not fully close. Spina bifida is one of the more
common types of neural tube defect.
What is the evidence?
How folic acid might affect cancer risk is not exactly clear.
Folic acid is needed to help cells make and repair DNA when they divide
to create new cells, and it may be involved in how cells turn certain
genes on and off. Scientists believe low levels of folic acid can lead
to changes in the chemicals that affect DNA, which may alter how well
cells can repair themselves or divide without making mistakes. This in
turn might lead to cancer.
Some studies that observed large groups have found a link
between lower intake of folic acid and a higher risk of certain
cancers. But these studies have been done at different times and have
looked at different populations around the world, which can make them
hard to interpret. The United States has enriched grain products with
folate since 1998. This means it’s likely that far fewer Americans are
now folic acid deficient than was the case in the past (or is the case
now in other countries). Therefore, it’s hard to know how the results
from previous studies might apply to people today, as the current
baseline folate levels here are likely higher.
Several studies that observed large groups of people have
found that folic acid may be linked to a lower risk of colon cancer. A
large study that tracked nurses in the United States from 1980 to 1994
reported that the women with a high intake of folic acid were much less
likely to get colon cancer than those with a lower intake. An even
larger study, involving both men and women, found a weaker link
overall, but noted that folic acid was more likely to be helpful in
those who had 2 or more alcoholic drinks a day.
Studies of folic acid and breast cancer have had mixed
results. The large study of nurses mentioned above found that folate
intake did not affect breast cancer risk overall, but women who had 1
or more alcoholic drinks a day and took in enough folate had lower
breast cancer risk than those who didn't. A 2003 study of more than
66,000 older women confirmed that women who drank more alcohol were
more likely to have breast cancer. In this study, however, the drinkers
with higher folic acid intakes did not have less breast cancer.
Some studies that observed large groups have found folic acid
is linked to lower rates of ovarian cancer in women who have at least 1
drink a day, but research in this area is not conclusive. Some research
has also suggested that folic acid may be linked to lower risk of
cancers of the pancreas, esophagus, and stomach. Further research to
clarify these findings is needed.
Whether or not folic acid works against cancer may also
depend on when it is taken. Some researchers fear that folic acid may
not be helpful, and could even be harmful, in people who already have
cancer or precancerous conditions. For example, 2 randomized,
controlled trials found that folic acid supplements had no effect on
already existing precancerous conditions of the cervix.
Overall, the evidence that folic acid can help prevent cancer
is promising but not conclusive. Further research involving randomized,
controlled clinical trials is needed to determine what effect folic
acid may have on the development of cancer.
At this time, it is hard to say how each nutrient or nutrient
combination affects a person’s risk of cancer. On the other hand,
studies of large groups of people have shown that those whose diets are
high in vegetables and low in animal fat, meat, and/or calories have
lower risks for some of the most common types of cancer. Until more is
known about this, the American Cancer Society recommends eating a
variety of healthful foods -- with most of them coming from plant
sources -- rather than relying on supplements. Choose whole grains over
refined grains and sugars, and limit high-fat and processed meats.
Select foods that help maintain a healthy weight. It is also important
to engage in moderate to vigorous physical activity for 30 to 60
minutes 5 or more days per week. For most people, this will help keep
weight under control, reduce risk of some cancers, and reap many other
health benefits. While it is best to get vitamins and minerals from
foods, supplements may be helpful for some people, such as pregnant
women, women of childbearing age, and people with restricted food
intakes. If a supplement is taken, the best choice for most people is a
balanced multivitamin/mineral supplement that contains no more than
100% of the "Daily Value" of most nutrients.
Are there any possible problems
or complications?
This product is sold as a dietary supplement in the
United States. Unlike drugs (which must be tested before being allowed
to be sold), the companies that make supplements are not required to
prove to the Food and Drug Administration that their supplements are
safe or effective, as long as they don't claim the supplements can
prevent, treat, or cure any specific disease.
Some such products may not contain the amount of the
herb or substance that is written on the label, and some may include
other substances (contaminants). Actual amounts per dose may vary
between brands or even between different batches of the same brand.
Most such supplements have not been tested to find
out if they interact with medicines, foods, or other herbs and
supplements. Even though some reports of interactions and harmful
effects may be published, full studies of interactions and effects are
not often available. Because of these limitations, any information on
ill effects and interactions below should be considered incomplete.
Folic acid is considered a safe and necessary dietary
nutrient. Because it is a water-soluble vitamin, most excess folic acid
is excreted in the urine. However, if taken in extremely large doses,
it may cause symptoms such as upset stomach or trouble sleeping. Folic
acid can also mask symptoms of vitamin B12 deficiency by correcting the
anemia caused by low vitamin B12 levels. However, the folic acid can't
correct the nervous system damage that low B12 levels can cause.
Continued B12 deficiency can allow this damage to become permanent.
Also, high doses of folate can worsen the nervous system damage. High
doses of folate may also interfere with the effectiveness of the
chemotherapy drug methotrexate and similar drugs. Always tell your
doctor and pharmacist about any supplements and herbs you are taking.
Relying on the use of supplements alone, and avoiding or
delaying conventional medical care, may have serious health
consequences.
Additional Resources
More Information From Your
American Cancer Society
The following information on complementary and alternative
therapies may also be helpful to you. These materials may be ordered
from our toll-free number (1-800-ACS-2345).
References
Feigelson HS, Jonas CR, Robertson AS, McCullough ML, Thun MJ,
Calle EE. Alcohol, folate, methionine, and risk of incident breast
cancer in the American Cancer Society Cancer Prevention Study II
Nutrition Cohort. Cancer Epidemiol Biomarkers Prev.
2003;12:161-164.
Giovannucci E, Stampfer MJ, Colditz GA, et al. Multivitamin
use, folate, and colon cancer in women in the Nurses’ Health Study. Ann
Intern Med. 1998;129:517-524.
Jacobs EJ, Connell CJ, Patel AV, et al. Multivitamin use and
colon cancer mortality in the Cancer Prevention Study II cohort (United
States). Cancer Causes Control. 2001;12:927-934.
Kushi LH, Byers T, Doyle C, et al. American Cancer Society
guidelines on nutrition and physical activity for cancer prevention:
reducing the risk of cancer with healthy food choices and physical
activity. CA Cancer J Clin. 2006;56:254–281.
Larsson SC, Giovannucci E, Wolk A. Dietary folate intake and
incidence of ovarian cancer: The Swedish Mammography Cohort. J
Natl Cancer Inst. 2004;96:396-402.
Mason JB, Levesque T. Folate: Effects on carcinogenesis and
the potential for cancer chemoprevention. Oncology (Huntingt).
1996;10:1727-1744.
MRC Vitamin Study Research Group. Prevention of neural tube
defects: Results of the Medical Research Council Vitamin Study. Lancet.
1991;338:131-137.
Office of Dietary Supplements, National Institutes of Health. Dietary
supplement fact sheet: Folate. 2005. Available at:
http://ods.od.nih.gov/factsheets/folate.asp#h8. Accessed April 18,
2007.
PDRhealth. Folate. Available at:
www.pdrhealth.com/drug_info/nmdrugprofiles/nutsupdrugs/fol_0110.shtml.
Accessed April 18, 2007.
Zhang S, Hunter DJ, Hankinson SE, et al. A prospective study
of folate intake and the risk of breast cancer. JAMA.
1999; 281:1632-1637.
Note: This information may not
cover all possible claims, uses, actions, precautions, side effects or
interactions. It is not intended as medical advice, and should not be
relied upon as a substitute for consultation with your doctor, who is
familiar with your medical situation.
Revised: 06/26/2007
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