Function:
Folate is a general term for one of the B vitamins that exists in many different chemical forms. Folate is involved in reactions that are critical for DNA function, and the formation of amino acids including the conversion of homocysteine to methionine.

Folic acid is the most stable form of folate but it is found rarely in food or in the body. However, it is the form used to provide folate in vitamin supplements and in fortified food products.

Recommended Dietary Allowance:
The Institute of Medicine has introduced a new unit called the Dietary Folate Equivalent (DFE). It reflects the higher availability of folic acid found in supplements and fortified foods compared to that of naturally occurring food folates.

Deficiency:
Anemia is a common finding with folate deficiency. A deficiency of either folate or vitamin B12 results in a similar kind of anemia. However, with B12 deficiency there are also abnormalities of the nervous system. Folate supplementation in B12 deficiency corrects the anemia but not the nervous system abnormalities.

Serum homocysteine levels increase with folate deficiency. Homocysteine elevation in the serum is associated with increased cardiovascular disease as well as higher death rates from all causes. Taking folic acid along with vitamins B6 and B12 decreases homocysteine. It is not yet known if this reduction influences the diseases associated with high homocysteine but it is a reasonable assumption. In the 1970's it was not known if lowering cholesterol influenced the rate of vascular disease but the assumption proved to be true.

Deficient folate intake in pregnancy results in an increase in congenital abnormalities in the newborn. These are primarily defects of the brain and spinal cord (neural tube defects).

Sources:
Folate is widely available in food but most plentiful in fresh green vegetables, citrus fruits and juices, and liver.

Foods required to be fortified are:

Breakfast cereals can add up to 400 mcg of folic acid per serving.

Toxicity and UL:
Administration of folate may mask the nervous system abnormalities of vitamin B12 deficiency and it is for this reason the UL has been set at 1,000 mcg per day.

Daily doses of over 15,000 mcg have been well tolerated for long periods of time but there is no apparent reason to take it at that level.

Recommendation:
Deficiency of folate has the potential for many harms. I have pointed out the problem of high serum homocysteine levels with insufficient intake as well as neural tube defects in infants born to folate deficient mothers. Supplemental folic acid is now being administered to the entire U.S. population who eat enriched grains and breakfast cereals.

Unless you regularly consume fortified foods I recommend 400 mcg of folic acid daily. Higher doses can be safely taken.

For more information visit:
http://osu.orst.edu/dept/lpi/infocenter/vitamins/fa/