The short answer is: pick folate.
Ahh prenatal vitamins. How does one choose? There are some things that are pretty consistent when it comes to prenatal vitamins. One thing I look is methylated folate instead of the synthetic folic acid. Some labels will read MTHF folate, methylfolate, 5-MTH, 5-5-methyltetrahydrofolatehas, L-5-MTHF, L-5-methyltetrahydrofolate, and (6S)-5-methyltetrahydrofolate, or (6S)-5-MTHF. The importance of this vitamin and its role in baby’s neural tube development is well documented. Of course, it plays many other roles in the body as well.
Folate has important advantages over synthetic folic acid – it is well absorbed even when gastrointestinal pH is altered, and its bioavailability (rate of absorption) is not affected by metabolic defects like MTHFR reductase polymorphism. Using folate instead of folic acid reduces the potential for masking symptoms of vitamin B12 deficiency and reduces interactions with certain drugs. Use of 5-MTHF also prevents the potential negative effects of unconverted folic acid in the peripheral circulation.
The Natalist MTHF Folate is made of 5-MTHF, the naturally occurring, predominant form of folate found in the body. Folate is recommended by the CDC and ACOG for all women of childbearing age to reduce the risk of spina bifida and other neural tube defects.‡
The problem with folic acid
Folic acid is man-made and needs to be broken down (metabolized) in order to be used properly by the body. Unmetabolized folic acid can accumulate in the body and over time can lead to some health consequences in the long-run. One study that I have come across suggests that high levels of folic acid is related to cognitive decline too.
Another concern I have is that prenatal folic acid supplementation may be linked to allergy risk in kiddos later in life. One study highlighted a positive association of folic acid supplementation in late pregnancy and asthma risk. In other words, high levels of folic acid later in pregnancy was related to higher risk of kids developing asthma as they got older. The authors point out that risk was not associated with folate intake.
Another study related allergy risk and folic acid suggested that folic acid exposure in utero is related to food allergy development in kids. In the study, scientists found that higher levels of unmetabolized folic acid measured at birth was associated with the development of food allergy.
The studies focusing on folic acid and allergy risk are very limited, and I do not want to come across as a fear-monger. Normally I do not base recommendations off of two studies. But with this allergy data compounded with so many other reasons why folate is shown to be preferred over folate, I feel like it is worth the extra cost to forego the folic acid in prenatal supplements.
Folate and IVF
Finally, if a woman is undergoing IVF, I like to recommend that she take over 800 mcg of folate in their prenatal vitamin. This is based off of a recent study suggesting a relationship between supplementation of certain micronutrients and higher chance of IVF success. One of these micronutrients is folic acid (folate), and taking in at least 833 mcg appears to offer some benefit. This is only based off of one study, but it is the only study I have come across that has given specific recommendations on folate supplementation amounts for IVF patients.
Want to learn more? Read Dr. Liz Kane’s article, MTHF Folate vs Folic Acid: What's Better for Prenatal Vitamins?