Genetics play a large role in autism, but exposure to environmental contaminants such as air pollution and pesticides likely contribute as well. A NIEHS workshop held June 21-22 explored whether certain nutrients can protect people from the harms of environmental exposures that may be linked to the likelihood of developing autism or related traits.
For two days, researchers from more than a dozen institutions across the country presented information related to the potential synergistic effects of certain foods and nutrients. They discussed what we know about the effects of nutritional interventions such as folate on autism spectrum disorders, and what we can learn from research on other health outcomes, such as the effects of consuming fish contaminated with methylmercury.
“While we normally think of reducing risk from chemical exposures in terms of removing or decreasing exposures, sometimes it can be difficult to achieve,” said Cindy Lawler, Ph.D., head of the Genes Branch, NIEHS Environment and Health. “An alternative is to focus on increasing beneficial nutritional exposures, such as folate or polyunsaturated fatty acids (PUFAs), on the assumption that these can mitigate the risk of harmful exposures.”
Effects of pollution and diet
Environmental exposures experienced before and during critical windows of pregnancy can have lasting health effects, such as autism spectrum disorders.
Traffic pollution can reduce reproductive potential in both males and females, couples who live near highways have a higher likelihood of infertility, says Audrey Gaskins, Sc.D., an epidemiologist at the Rollins School of Public Health at Emory University. She reviewed data from the Environment and Reproductive Health Study, focusing on couples at the Massachusetts General Hospital Fertility Center between 2004 and 2019. participants’ diet, medical and reproductive histories, as well as residential addresses, which researchers linked to air pollution patterns across six cycles of fertilization.
Gaskins hypothesized that air pollution could impair reproduction through various biological mechanisms, including oxidative stress, endocrine disruption, DNA methylation, impaired immune response, and inflammation. . The greater the air pollution, the greater the decrease in participants’ reproductive success. Folic acid, a synthetic form of folate, however, appears to counteract these effects. The more folic acid a pregnant woman took, the higher the likelihood of a live birth.
“Clearly a lot more research is needed,” said Gaskins, whose work was funded by a NIEHS grant. “There are very few preconception cohorts that measure both dietary and environmental exposures.”
Benefits of folic acid
The benefits of folic acid extend beyond reproduction. Often taken by pregnant women as a multivitamin to reduce the risk of spina bifida, the supplement may also reduce the risk of autism.
“We don’t have interventions that are good prevention strategies for these neurodevelopmental disorders” like autism and schizophrenia, said Joshua Roffman, MD, director of the Early Brain Development Initiative at Massachusetts General Hospital. Yet folic acid is safe, widely available, and could be used to reduce risk.
Research published in 2019 by Rebecca Schmidt, Ph.D., a molecular epidemiologist from the University of California, Davis showed an associated reduced risk of autism in younger siblings when their mothers took a prenatal vitamin with folic acid during pregnancy. Among 241 children whose older siblings had autism spectrum disorders, 32% developed autism when their mother did not take a prenatal vitamin during the first month of pregnancy, compared to 14% when their mother taken a vitamin supplement. Fortified breads and cereals now contain folic acid, but increasing the number and type of foods fortified with the vitamin could further reduce the risk.
Other components of a prenatal vitamin or supplements such as vitamin D or polyunsaturated fatty acids may also have beneficial effects on neurodevelopment. “We need more studies on the potential mechanisms that these exposures share, and that could help us understand how to advance risk mitigation strategies,” Schmidt said.
It is complicated
Although a growing body of research points to the potential protective effects of nutrition on autism spectrum disorders, only a handful of nutrients have been examined to explore the link. Presenters cautioned that efforts to study nutrition interventions should also consider dose, timing, equity and access to treatment.
“I think it’s an exciting area of research, but we should be very careful that nutritional interventions aren’t as easy as we think they are,” said Youssef Oulhote, Ph.D.environmental epidemiologist at the University of Massachusetts Amherst, who co-organized the meeting with Kristen Lyall, Sc.D.epidemiologist at Drexel University.
“The workshop was a great way to think more deeply about the methods we should be using and the questions we should be asking,” Lyall noted.
(Susan Cozier is a contract writer for the NIEHS Office of Communications and Public Liaison.)