Re: Folate
- From: rpautrey2 <rpautrey2@xxxxxxxxx>
- Date: Wed, 19 Dec 2007 18:53:53 -0800 (PST)
Folate
Folate and folic acid are forms of a water-soluble B vitamin. Folate
occurs naturally in food. Folic acid is the synthetic form of this
vitamin that is found in supplements and fortified foods. A key
observation of researcher Lucy Wills nearly 70 years ago led to the
identification of folate as the nutrient needed to prevent the anemia
of pregnancy. Dr. Wills demonstrated that the anemia could be
corrected by a yeast extract. Folate was identified as the corrective
substance in yeast extract in the late 1930s and was extracted from
spinach leaves in 1941.
Folate is necessary for the production and maintenance of new cells.
This is especially important during periods of rapid cell division and
growth such as infancy and pregnancy. Folate is needed to make DNA and
RNA, the building blocks of cells. It also helps prevent changes to
DNA that may lead to cancer. Both adults and children need folate to
make normal red blood cells and prevent anemia.
What foods provide folate?
Leafy greens such as spinach and turnip greens, dry beans and peas,
fortified cereals and grain products, and some fruits and vegetables
are rich food sources of folate. Some breakfast cereals (ready-to-eat
and others) are fortified with 25% or 100% of the Daily Value (DV) for
folic acid. The table of selected food sources of folate and folic
acid suggests dietary sources of this vitamin.
Since 1998, food manufacturers in the US have been required to add
folic acid to enriched breads, cereals, flours, corn meals, pastas,
rice, and other grain products. These regulations were specifically
targeted to reduce the risk of neural tube birth defects in newborns.
Since the folic acid fortification program took effect, fortified
foods have become a major source of folic acid in the American diet.
Synthetic folic acid that is added to fortified foods and dietary
supplements has a simpler chemical structure than the natural form of
folate, and is absorbed more easily by the body. After digestion and
absorption however, the two forms are identical and function in
exactly the same manner.
How much folate do we need?
The Recommended Dietary Allowance (RDA) is the average daily dietary
intake level that is sufficient to meet the nutrient requirements of
nearly all (97-98%) healthy individuals in each life-stage and gender
group. The 1998 RDAs for folate are expressed in a term called the
Dietary Folate Equivalent. The Dietary Folate Equivalent (DFE) was
developed to help account for the differences in absorption of
naturally occurring dietary folate and the more bioavailable synthetic
folic acid (1 mcg of food folate = 0.6 mcg folic acid from supplements
and fortified foods).
The 1998 RDAs for folate expressed in micrograms (mcg) of DFE for
adult men and women (aged 19 years and older) is 400 mcg. During
pregnancy the daily intake should be increased to 500 mcg, and the RDA
for breastfeeding women is 500 mcg.
The National Health and Nutrition Examination Survey (NHANES III
1988-91) and the Continuing Survey of Food Intakes by Individuals
(1994-96 CSFII) indicated that most adults did not consume adequate
folate. However, the folic acid fortification program has increased
folic acid content of commonly eaten foods such as cereals and grains,
and as a result diets of most adults now provide recommended amounts
of folate equivalents.
When can folate deficiency occur?
A deficiency of folate can occur when your need for folate is
increased, when dietary intake of folate is inadequate, and when your
body excretes (or loses) more folate than usual. Medications that
interfere with your body's ability to use folate may also increase the
need for this vitamin. Some situations that increase the need for
folate include:
pregnancy and lactation (breastfeeding)
alcohol abuse
malabsorption
kidney dialysis
liver disease
certain anemias.
Some medications interfere with the body's ability to utilize folate,
including:
anti-convulsant medications such as dilantin, phenytoin, and
primidone
Metformin, sometimes prescribed to control blood sugar in type 2
diabetes
Sulfasalazine, used to control inflammation associated with Crohn's
disease and ulcerative colitis)
Triamterene, a diuretic
Methotrexate, used in the treatment of some types of cancer, severe
psoriasis, and adult rheumatoid arthritis.
Signs of folate deficiency
Signs of folic acid deficiency are often subtle. Diarrhea, loss of
appetite, and weight loss can occur. Additional signs are weakness,
sore tongue, headaches, heart palpitations, irritability, and
behavioral disorders. Women with folate deficiency who become pregnant
are more likely to give birth to low birth weight and premature
infants, and infants with neural tube defects. In adults, anemia is a
sign of advanced folate deficiency.
In infants and children, folate deficiency can slow growth rate. Some
of these symptoms can also result from a variety of medical conditions
other than folate deficiency. It is important to have a physician
evaluate these symptoms so that appropriate medical care can be
given.
Who may need extra folic acid to prevent a deficiency?
Women of childbearing age, people who abuse alcohol, anyone taking
anti-convulsants or other medications that interfere with the action
of folate, individuals diagnosed with anemia from folate deficiency,
and individuals with malabsorption, liver disease, or who are
receiving kidney dialysis treatment may benefit from a folic acid
supplement.
Folic acid is very important for all women who may become pregnant.
Adequate folate intake during the periconceptual period, the time just
before and just after a woman becomes pregnant, protects against a
number of congenital malformations including neural tube defects.
Neural tube defects result in malformations of the spine called spina
bifida, and of the skull, and brain anencephaly. The risk of neural
tube defects is significantly reduced when supplemental folic acid is
consumed in addition to a healthful diet prior to and during the first
month following conception.
Women who could become pregnant are advised to eat foods fortified
with folic acid or take supplements in addition to eating folate-rich
foods to reduce the risk of some serious birth defects. Taking 400
micrograms of synthetic folic acid daily from fortified foods and/or
supplements has been suggested. The Recommended Dietary Allowance
(RDA) for folate equivalents for pregnant women is 600 micrograms.
Folate deficiency has been observed in alcoholics. A 1997 review of
the nutritional status of chronic alcoholics found low folate status
in more than 50 percent of those surveyed. Alcohol interferes with the
absorption of folate and increases excretion of folate by the kidney.
In addition, many alcohol abusers have poor quality diets that do not
provide the recommended intake of folate. Increasing folate intake
through diet, or folic acid intake through fortified foods or
supplements, may be beneficial to the health of alcoholics.
Anti-convulsant medications such as dilantin increase the need for
folate. Anyone taking anti-convulsants and other medications that
interfere with the body's ability to use folate should consult with a
medical doctor about the need to take a folic acid supplement.
Anemia is a condition that occurs when red blood cells cannot carry
enough oxygen. It can result from a wide variety of medical problems,
including folate deficiency. Folate deficiency can result in the
formation of large red blood cells that do not contain adequate
hemoglobin, the substance in red blood cells that carries oxygen to
your body's cells. Your physician can determine whether an anemia is
associated with folate deficiency and whether supplemental folic acid
is indicated.
Several medical conditions increase the risk of folic acid deficiency.
Liver disease and kidney dialysis increase excretion (loss) of folic
acid. Malabsorption can prevent your body from using folate in food.
Medical doctors treating individuals with these disorders will
evaluate the need for a folic acid supplement.
What is the health risk of too much folic acid?
The risk of toxicity from folic acid is low. The Institute of Medicine
has established a tolerable upper intake level (UL) for folate of
1,000 mcg for adult men and women, and a UL of 800 mcg for pregnant
and lactating (breast-feeding) women less than 18 years of age.
Supplemental folic acid should not exceed the UL to prevent folic acid
from masking symptoms of vitamin B12 deficiency.
Caution about folic acid supplements
Beware of the interaction between vitamin B12 and folic acid.
Folic acid supplements can correct the anemia associated with vitamin
B12 deficiency, but folic acid will not correct changes in the nervous
system that result from vitamin B12 deficiency. Permanent nerve damage
can occur if vitamin B12 deficiency is not treated. Intake of
supplemental folic acid should not exceed 1,000 micrograms (mcg) per
day to prevent folic acid from masking symptoms of vitamin B12
deficiency.
It is very important for older adults to be aware of the relationship
between folic acid and vitamin B12 because they are at greater risk of
having a vitamin B12 deficiency. If you are 50 years of age or older,
ask your physician to check your B12 status before you take a
supplement that contains folic acid.
Current Issues and Controversies about Folate
Folic acid and heart disease
A deficiency of folate, vitamin B12, or vitamin B6 may increase your
level of homocysteine, an amino acid normally found in your blood.
There is evidence that an elevated homocysteine level is an
independent risk factor for heart disease and stroke. The evidence
suggests that high levels of homocysteine may damage coronary arteries
or make it easier for blood clotting cells called platelets to clump
together and form a clot. However, there is currently no evidence
available to suggest that lowering homocysteine with vitamins will
reduce your risk of heart disease. Clinical intervention trials are
needed to determine whether supplementation with folic acid, vitamin
B12 or vitamin B6 can lower your risk of developing coronary heart
disease.
Folic acid and cancer
Some evidence associates low blood levels of folate with a greater
risk of cancer. Folate is involved in the synthesis, repair, and
functioning of DNA, our genetic map, and a deficiency of folate may
result in damage to DNA that may lead to cancer. Several studies have
associated diets low in folate with increased risk of breast,
pancreatic, and colon cancer. Findings from a study of over 121,000
nurses suggested that long-term folic acid supplementation (for 15
years) was associated with a decreased risk of colon cancer in women
aged 55 to 69 years of age. However, associations between diet and
disease do not indicate a direct cause. Researchers are continuing to
investigate whether enhanced folate intake from foods or folic acid
supplements may reduce the risk of cancer. Until results from such
clinical trials are available, folic acid supplements should not be
recommended to reduce the risk of cancer.
Folic acid and methotrexate for cancer
Folate is important for cells and tissues that rapidly divide. Cancer
cells divide rapidly, and drugs that interfere with folate metabolism
are used to treat cancer. Methotrexate is a drug often used to treat
cancer because it limits the activity of enzymes that need folate.
Unfortunately, methotrexate can be toxic, producing side effects such
as inflammation in the digestive tract that make it difficult to eat
normally. Leucovorin is a form of folate that can help "rescue" or
reverse the toxic effects of methotrexate. It is not known whether
folic acid supplements can help control the side effects of
methotrexate without decreasing its effectiveness in chemotherapy. It
is important for anyone receiving methotrexate to follow a medical
doctor's advice on the use of folic acid supplements.
Folic acid and methotrexate for non-cancerous diseases
Low dose methotrexate is used to treat a wide variety of non-cancerous
diseases such as rheumatoid arthritis, lupus, psoriasis, asthma,
sarcoidoisis, primary biliary cirrhosis, and inflammatory bowel
disease. Low doses of methotrexate can deplete folate stores and cause
side effects that are similar to folate deficiency. Both high folate
diets and supplemental folic acid may help reduce the toxic side
effects of low dose methotrexate without decreasing its effectiveness.
Anyone taking low dose methotrexate for the health problems listed
above should consult with a physician about the need for a folic acid
supplement.
Food sources of folate and folic acid
Green leafy vegetables, dry beans and peas, and many other types of
vegetables and fruits are good sources of folate. In addition,
fortified foods are a major source of folic acid. It is not unusual to
find foods such as cereals fortified with 100 percent of the RDA for
folate. The variety of fortified foods available has made it easier
for women of childbearing age to consume the recommended 400 mcg of
folic acid per day from fortified foods and/or supplements. The large
numbers of fortified foods on the market, however, also raise concern
that intake may exceed the UL. This is especially important for anyone
at risk of vitamin B12 deficiency, which can be masked by too much
folic acid. It is important for anyone who is considering taking a
folic acid supplement to first consider whether their needs are being
met by adequate sources of dietary folate and folic acid from
fortified foods.
Ready to eat cereal, fortified with 100% of the DV, 3/4 c: 400 mcg ~
100% of Daily Value (DV)
Beef liver, cooked, braised, 3 oz: 185 mcg ~ 45% DV
Cowpeas (blackeyes), immature, cooked, boiled, 1/2 c: 105 mcg ~ 25%
DV
Spinach, frozen, cooked, boiled, 1/2 c: 100 mcg ~ 25% DV
Great Northern beans, boiled, 1/2 c: 90 mcg ~ 20% DV
Asparagus, boiled, 4 spears: 85 mcg ~ 20% DV
Wheat germ, toasted, 1/4 c: 8o mcg ~ 20% DV
Orange juice, 3/4 c: 70 mcg ~ 20% DV
Vegetarian baked beans, canned, 1 c: 60 mcg ~ 15% DV
Spinach, raw, 1 c: 60 mcg ~ 15% DV
Rice, white, long-grain, parboiled, cooked, enriched, 1/2 c: 45 mcg ~
10% DV
Avocado, 1/2 c sliced: 45 mcg ~ 10% DV
Information provided by
National Institutes of Health
Article Created: 2001-03-07
Article Updated: 2001-03-07
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