During pregnancy, healthcare providers often advise expectant parents on what to avoid, such as certain types of fish due to heavy metal risks, and what to include, like omega-3 fatty acids and folic acid, to support healthy development. Folic acid, in particular, is known for preventing neural tube defects. However, new research suggests the relationship between folic acid and brain development, including the risk of autism spectrum disorder (ASD), may be more complex than once thought.
In this article, we explore the latest scientific findings on folic acid and folate during pregnancy, highlighting how both low and excessive levels may impact a child’s neurodevelopment. We also provide guidance on what expecting parents should consider when it comes to supplementation.
Too Much of a Good Thing? The Autism Connection
A major study from the Johns Hopkins Bloomberg School of Public Health, involving data from the Boston Birth Cohort, has brought attention to the potential risks of excessive folate. Researchers found that mothers with extremely high folate levels, more than four times the recommended amount, right after childbirth were twice as likely to have a child later diagnosed with ASD. When both folate and vitamin B12 were excessively high, the risk increased more than 17 times.
This finding challenges the idea that more supplementation is always better. While folate deficiency remains a serious concern, maintaining optimal, not excessive, levels is crucial. Since nearly one in four U.S. women of childbearing age still do not meet recommended folate levels, and routine monitoring is uncommon, the study underscores the need for clearer, more personalised guidelines.
Protective Effects with a Caveat
A recent systematic review supports the importance of folic acid supplementation before and during early pregnancy. It confirms that folic acid can promote healthy brain development and may reduce the risk of ASD. However, the review also raises concerns about high intake levels, particularly when folic acid from supplements is combined with that from fortified foods.
Some research suggests a U-shaped relationship, where both low and high folic acid levels are associated with increased risks, while moderate intake is most beneficial. These mixed results highlight the need for more targeted research to define safe and effective dosing, considering genetic and metabolic differences among individuals.
Emerging Risks of Over-Supplementation
The role of folic acid in supporting DNA synthesis, methylation, and neurotransmitter production is well established. It has been instrumental in reducing neural tube defects worldwide. However, evidence now suggests that too much folic acid, particularly in the form of unmetabolised folic acid from excessive supplementation, may interfere with brain development.
According to the review "The Concept of Folic Acid in Health and Disease," high folic acid levels, especially when combined with elevated vitamin B12, have been linked to an increased risk of ASD in children. This underscores the importance of precise dosing and carefully timed supplementation during critical periods of foetal development.
The Role of Genetics and Better Supplement Options
A key factor in folic acid metabolism is how the body converts it into methylfolate, the bioactive form used by cells. For individuals with an MTHFR gene mutation, this conversion process is impaired, leading to reduced ability to properly absorb and utilise folate. This genetic variant is relatively common and may increase the risk of adverse effects from standard folic acid supplementation.
Because of this, some experts recommend choosing methylfolate supplements instead of synthetic folic acid, particularly for individuals known to have the MTHFR mutation. This ensures the body receives folate in a form it can use efficiently, supporting healthy foetal development while reducing the risk of overexposure.
Takeaway: A Balanced Approach to Folate in Pregnancy
Folic acid remains essential for a healthy pregnancy, especially in the early stages when the baby's brain and spinal cord are developing. However, emerging research shows that balance is key. Both deficiencies and excessive levels of folic acid may pose risks, particularly regarding the development of ASD.
Expecting parents should work closely with healthcare providers to assess individual needs, consider genetic factors, and potentially opt for methylfolate supplementation when appropriate. With better awareness and personalised guidance, it's possible to support both maternal health and optimal neurodevelopment for the baby.