No, folic acid is not toxic? A dietitian explains the supplement’s importance

Folic acid is not the same thing as folate, although people use the words interchangeably. Even medical doctors, dietitians, and other practitioners get the two mixed up. Recently, health gurus online have made it their new obsession to villainize folic acid because it is a synthetic form of folate. But is the criticism warranted?

Folic acid is the fully oxidized, synthetic form of folate that is used for fortification in refined grains. It is also what you will find in most supplements. It’s much more stable and, therefore, practical for adding to common foods like bread and flour.

You may have heard that pregnant women should supplement folic acid to prevent neural tube defects. This is because studies have consistently shown that folic acid helps to do just that. As such, in 1992, the U.S. Public Health Service recommended that all women who can become pregnant get 400 micrograms (mcg) of folic acid every day.

In 1998, the Institute of Medicine’s Food and Nutrition Board of the National Academy of Sciences recommended that all pregnant women supplement folic acid and/or eat fortified foods containing it. In the same year, the United States started a public health intervention that required manufacturers to fortify enriched cereals with 140 mcg of folic acid per two-thirds cups of flour. It was after this that pregnancies in the United States saw a drop in babies born with neural tube defects.

Folate (vitamin B9) is naturally occurring in foods like dark leafy greens and beef liver. It can also be found in supplements, although not nearly in the same amounts as folic acid. It is a bit more unstable depending on the food it’s present in. Current research shows that processes like canning and freezing may reduce folate content in vegetables, while amounts in animal livers remain more stable.

Fresh raw beef liver
Raw beef livers on a black stone cutting board. (© Dmitriy Melnikov – stock.adobe.com)

Do our bodies process synthetic folic acid?

With the rise of “genetic mutation” talk, many are now convinced that they cannot process folic acid if they have a mutation in the gene that codes for methylenetetrahydrofolate reductase (MTHFR). This is a misleading statement that has even made people go so far as to think that nobody can process folic acid just because it is synthetic.

Folic acid would not have been shown to reduce neural tube defects if the body did not process it properly. Folic acid is able to be processed by an enzyme called dihydrofolate reductase (DHFR). This is completely unrelated to MTHFR, which comes in at step four of folic acid metabolism.

For most people, DHFR works sufficiently to process folic acid. However, there are concerns that the amount of folic acid in refined grains, which make up a large portion of the standard American diet, provides too much folic acid at once for the body to handle. Studies have shown that only a relatively small amount of DHFR is produced each day. Natural food folate, on the other hand, does not need to go through this enzyme.

Generally speaking, the body knows how much to take and excretes the rest in your urine. However, there have been studies which show that in higher amounts, unmetabolized folic acid may be left in the body. This has been hypothesized to contribute to the progression and exacerbation of certain cancers. This is a growing area of study that many researchers would like to explore more thoroughly, but there is nothing definitive yet.

Should pregnant women take folic acid?

Current guidelines recommend that pregnant women take folic acid to reduce the risk of neural tube defects. No studies have examined alternate supplement forms, such as methylfolate or folinic acid (two forms that do not need to be converted by DHFR and are touted as more bioavailable). As always, speak with your doctor about your unique medical needs.

Bottom Line

Folic acid and folate metabolism, particularly related to genetic variations, are two rapidly growing areas of research. However, what has been well-studied is that folic acid can significantly reduce the risks of neural tube defects in pregnancy. It is also true that the body can process folic acid, although there is nuance attached to the general effectiveness and safety of high intake. For most people, consumption of folic acid is likely not harmful, and is definitely better than a folate deficiency.

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