Women who plan to become pregnant are told they need enough folate to prevent birth defects, but new research suggests there could be serious risks in having far too much of the nutrient.
The researchers 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.
“This research suggests that this could be the case of too much of a good thing.”
Further, very high levels of another vitamin, B12, are also potentially harmful, tripling the risk that a new mom’s 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; the synthetic version, folic acid, is used to fortify cereals and breads in the United States and in vitamin supplements.
“Adequate supplementation is protective: That’s still the story with folic acid,” says senior author M. Daniele Fallin, director of the Bloomberg School’s Wendy Klag Center for Autism and Developmental Disabilities at Johns Hopkins University. “We have long known that a folate deficiency in pregnant mothers is detrimental to her child’s development. But what this tells us is that excessive amounts may also cause harm. We must aim for optimal levels of this important nutrient.”
Folate is essential in cell growth and promotes neurodevelopmental growth. Deficiencies early in pregnancy have been linked to serious birth defects–-spina bifida and anencephaly—and to an increased risk of developing an autism spectrum disorder. Despite a push to ensure women get adequate folate, some still don’t get enough or their bodies aren’t properly absorbing it, leading to deficiencies.
The Centers for Disease Control and Prevention says that one in four women of reproductive age in the United States has insufficient folate levels. Levels are not routinely monitored during pregnancy.
Autism spectrum disorder is a neurodevelopmental condition involving social impairment, abnormal communication, and repetitive or unusual behavior. One in 68 children in the United States has the disorder, with boys five times more likely than girls to develop it. The causes remain unclear, but research suggests the factors are a combination of genes and the environment.
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 children’s births between 1998 and 2013 and followed for several years; mothers’ blood folate levels were checked within the first one to three days after delivery. One in 10 had what is considered an excess amount of folate (more than 59 nanomoles per liter) and 6 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. There are not well-established thresholds for adequate vitamin B12 levels.
A large majority of the mothers in the study reported having taken multivitamins—including folic acid and vitamin B12—throughout pregnancy. But the researchers say they don’t know exactly why some had such high levels in their blood. It could be that they consumed too many folic acid-fortified foods or took too many supplements. Some women may be genetically predisposed to absorbing greater quantities of folate or metabolizing it more slowly. Or it could be a combination of the two.
More research is needed, the scientists say, to determine just how much folic acid a woman should consume during pregnancy to have the best chance for optimal blood folate levels.
With many vitamin supplements, the conventional wisdom is 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 research suggests that this could be the case of too much of a good thing,” says lead author Ramkripa Raghavan, a doctoral student in population, family, and reproductive health. “We tell women to be sure to get folate early in pregnancy. What we need to figure out now is whether there should be additional recommendations about just what an optimal dose is throughout pregnancy.”
Researchers presented their preliminary findings at the 2016 International Meeting for Autism Research in Baltimore. The study is part of an ongoing prospective birth cohort study on early life determinants of autism in the Boston Birth Cohort and is supported by the Maternal and Child Health Bureau.
Source: John Hopkins University