High folate and vitamin B12 levels and autism risk

Researchers from Johns Hopkins Bloomberg School of Public Health have found that if a new mother has a very high level of folate right after giving birth – more than four times what is considered adequate – the risk that her child will develop an autism spectrum disorder doubles. Very high vitamin B12 levels in new moms are also potentially harmful, tripling the risk that her offspring will develop an autism spectrum disorder. If both levels are extremely high, the risk that a child develops the disorder increases 17.6 times. Folate, a B vitamin, is found naturally in fruits and vegetables, while the synthetic version, folic acid, is used to fortify cereals and breads in the United States and in vitamin supplements.

The preliminary findings will be presented May 13 at the 2016 International Meeting for Autism Research in Baltimore. While it was known that  folate deficiency in pregnant mothers is detrimental to the child’s development. the current research suggests that excessive amounts may also cause harm.

Folate is essential in cell growth and promotes neurodevelopmental growth. Deficiencies early in pregnancy have been linked to birth defects and to an increased risk of developing an autism spectrum disorder. The Centers for Disease Control and Prevention says that one in four women of reproductive age in the U.S. have insufficient folate levels. Levels are not routinely monitored during pregnancy.

Autism spectrum disorder is a neurodevelopmental condition characterized by social impairment, abnormal communication and repetitive or unusual behavior. 

For the study, researchers analyzed data from 1,391 mother-child pairs in the Boston Birth Cohort, a predominantly low-income minority population.

The mothers were recruited at the time of their child’s birth between 1998 and 2013 and followed for several years, with the mother’s blood folate levels checked once within the first one to three days of delivery. The researchers found that one in 10 of the women had what is considered an excess amount of folate (more than 59 nanomoles per liter) and six percent had an excess amount of vitamin B12 (more than 600 picomoles per liter).

The World Health Organization says that between 13.5 and 45.3 nanomoles per liter is an adequate amount of folate for a woman in her first trimester of pregnancy. Unlike with folate, there are not well-established thresholds for adequate vitamin B12 levels.

A large majority of the mothers in the study reported having taken multivitamins – which would include folic acid and vitamin B12 – throughout pregnancy. But the researchers say they don’t know exactly why some of the women had such high levels in their blood. It could be that they consumed too many folic acid-fortified foods or took too many supplements. Or, they say, it could be that some women are genetically predisposed to absorbing greater quantities of folate or metabolizing it slower, leading to the excess. Or it could be a combination of the two.

More research is needed in order to determine just how much folic acid a woman should consume during pregnancy to have the best chance that she will have optimal blood folate levels to ensure her offspring’s health. With many types of vitamin supplements, the conventional wisdom has been that too much is not harmful, that the body will flush out the excess. That may not be the case with folic acid and vitamin B12.

This study is part of an ongoing prospective birth cohort study on early life determinants of autism in the Boston Birth Cohort, co-led by Fallin and Wang, MD, MPH, ScD, Zanvyl Krieger Professor, Director, Center on the Early Life Origins of Disease at Bloomberg School, and is supported by the Maternal and Child Health Bureau (R40MC27443).

However it has to be stressed that the above study has not shown a causal link between taking folic acid and autism. The researchers took blood tests of close to 1,400 mothers between one to three days after they gave birth and found that about 10% of the mothers had very high levels of folate, beyond recommended amounts, and that these women were also more likely to have a baby that would later be diagnosed with autism spectrum disorder.

On May 10, the United States Preventative Services Task Force released a draft update to its existing recommendations on folic acid, and once again the group is advising all women who are planning or capable of getting pregnant take a daily supplement of 0.4 to 0.8 mg of folic acid.

It is also important to note that the above study is presented at a conference and have not been peer-reviewed or published in a journal.