The Importance of Folic Acid in the Prevention of Neural Tube Defects
Folic acid is a water soluble vitamin, also known as vitamin B9. It is found in leafy green vegetables, legumes, nuts, seeds, orange juice, yeasts, and liver (1). Folic acid is important for the synthesis of DNA and RNA, and for the metabolism of amino acids. It plays a role in cell division and growth, and is therefore essential for the development of the neural tube (1).
Neural tube defects (NTDs) are congenital malformations of the brain and spine. They occur when the neural tube does not close properly during embryonic development (2). NTDs are a significant cause of death and disability in newborn infants (2). The most common type of NTD is spina bifida, which affects the spinal cord. Other types of NTD include anencephaly and encephalocele (2).
Folic acid has been shown to prevent NTDs. In countries where flour is fortified with folic acid, the incidence of NTDs has decreased (3). The risk of concurrence and recurrence of the general abnormalities are minimized by the application of peri-conceptional folic acid supplementation (3).
2. Folic acid and neural tube defects
Folic acid is important for the development of the neural tube. The neural tube forms during embryonic development and becomes the brain and spinal cord (4). Folic acid is required for DNA synthesis and cell division. If there is insufficient folic acid, the neural tube does not develop properly and NTDs can occur (4).
Folic acid deficiency is common in pregnant women. It has been estimated that up to 50% of pregnant women globally have inadequate levels of folic acid (5). This is because the demand for folic acid increases during pregnancy, but dietary intake often does not meet these requirements (5). Folic acid deficiency can lead to megaloblastic anaemia, which can cause fatigue, shortness of breath and heart palpitations (5). Folic acid deficiency can also increase the risk of NTDs (5).
The most effective way to reduce the risk of NTDs is to ensure that women have adequate levels of folic acid before they become pregnant (6). This can be achieved through dietary fortification or supplementation (6). Folic acid supplementation has been shown to reduce the risk of NTDs by up to 70% (7).
3. Fortification of bread with folic acid
Bread is a major source of dietary folate in many countries. It is usually made from wheat flour, which contains low levels of folic acid (8). In order to increase the level of folic acid in bread, wheat flour can be fortified with synthetic folic acid (8).
Fortification of flour with folic acid was first introduced in the United States in 1996 (9). This was followed by fortification programs in Canada and several European countries (9). In 1998, Australia and New Zealand became the first countries to mandate fortification of all breadmaking flour with folic acid (10). As a result of these fortification programs, the prevalence of NTDs has decreased in these countries (10).
4. Australia, New Zealand, Canada and the United States
Australia and New Zealand were the first countries to mandate fortification of all breadmaking flour with folic acid. This policy was introduced in 1998 and has been successful in reducing the prevalence of NTDs (10).
Canada introduced fortification of flour with folic acid in 1998. A recent study found that fortification has resulted in a significant reduction in the prevalence of NTDs (11).
The United States introduced fortification of flour with folic acid in 1996. A study published in 2009 found that fortification has resulted in a significant reduction in the prevalence of NTDs (12).
5. Recommendations for peri-conceptional folic acid supplementation
The following groups of women are at increased risk of having a baby with an NTD and should take a daily supplement of 400 micrograms (μg) of folic acid for at least one month before conception and during early pregnancy:
– women who have had a previous baby with an NTD
– women who are taking certain medications, such as antiepileptic drugs
– women who have certain medical conditions, such as diabetes
– women who have had surgery to the uterus or ovaries
– women who are obese
– women who are vegans or vegetarians
– women who are from certain ethnic groups, such as Asian or African descent (13)
Folic acid is important for the development of the neural tube. Neural tube defects are a significant cause of death and disability in newborn infants. The most effective way to reduce the risk of neural tube defects is to ensure that women have adequate levels of folic acid before they become pregnant. This can be achieved through dietary fortification or supplementation.