A study recent found that the mothers of autistic boys drank over three times more diet sodas during pregnancy than the mothers of non-autistic boys. This difference was absent in mothers of girls. The study was published in Nutrients.
Autism spectrum disorder is a category of neurodevelopmental disorders characterized by challenges in social interaction, communication, and repetitive behaviors. The term “spectrum” reflects the wide variation in symptoms and severity that individuals with autism spectrum disorder can experience. This disorder is typically diagnosed in early childhood, and its impact on daily functioning can vary widely.
The share of children suffering from autism has risen dramatically in the past 40 years in the United States. Numbers went from 0.3 per 1000 children before 1980 to 27.6 per 1000 children in 2020. This increase is largely, but not entirely, due to better testing and diagnostics. Researchers are intensely studying whether there are other factors that made autism more common.
One point many researchers look at are conditions in the uterus during pregnancy and, consequently, the lifestyle of mothers and their dietary habits. Studies indicate that maternal intake of vitamins, folic acid, omega-6 fatty acids, and a number of other substances during pregnancy are associated with a reduced risk of autism in children.
In contrast, higher intake of methanol has been linked to an increased risk of autism in children. The primary source of dietary methanol is aspartame, a widely used artificial sweetener. During digestion, aspartame breaks down into two amino acids (aspartic acid and phenylalanine) and methanol. Although the U.S. Food and Drug Administration has approved aspartame as a tabletop sweetener, these findings suggest that pregnant women might unknowingly expose their unborn children to an increased risk of autism by consuming products sweetened with aspartame.
Aspartame is mainly used in diet sodas, so study author Sharon Parten Fowler and her colleagues wanted to explore whether the quantity of diet sodas consumed during pregnancy or the equivalent amount of aspartame (calculated from data on diet soda intake) differs in mothers of children with and without autism. Noting that the risk of autism is 4 times higher in boys than in girls, they also wanted to make comparisons within sexes.
The study involved 235 families with at least one child diagnosed with autism spectrum disorder and 121 families with non-autistic children. Recruitment was conducted through the University of Texas Health Science Center at San Antonio between 2011 and 2014, as well as through media in San Antonio and southern Texas.
Parents provided information about their households, demographic details about the children, and whether each child had been diagnosed with autism spectrum disorder, Asperger’s disorder, pervasive developmental disorder—not otherwise specified, or childhood disintegrative disorder. Children diagnosed with any of these disorders were included in the autism spectrum disorder group. Researchers also inquired if there was a period when their child started using “at least three words” they could understand and then stopped talking for a while. Children whose parents answered “No” to this question were further classified as non-regressive autism spectrum disorder cases.
Biological mothers of the children completed a retrospective questionnaire about their consumption of diet sodas and other diet drinks during pregnancy and breastfeeding. They reported the number of cans or bottles of diet sodas or other diet drinks consumed in a specified time unit. The questionnaire also inquired about the frequency of low-calorie sweetener use during pregnancy (such as Sweet ‘N Low, Equal, or Splenda).
The researchers divided mothers into two groups based on their reported diet soda consumption during pregnancy – those drinking up to one can of diet soda per day and those drinking more than that. Similarly, after estimating the likely amounts of aspartame from all diet beverages and low-calorie sweeteners, mothers were categorized into those consuming up to 177 milligrams of aspartame per day and those consuming more.
Results showed that shares of mothers with high intake of aspartame and diet sodas during pregnancy increased sharply with the severity of autism symptoms in boys. Approximately 25% of mothers of boys with non-regressive autism (a more severe form of the disorder) fell into the high aspartame intake category. In comparison, 22.1% of these mothers consumed more than one diet soda per day during pregnancy, while only 7.4% of the control group (mothers of non-autistic boys) did so.
Interpreted in a different way, odds of high exposure to dietary soda in utero progressively increased with the increasing severity of autism symptoms. The odds of exposure to diet soda and aspartame in utero were more than tripled in boys with autism compared to boys without this disorder.
These associations were completely absent in girls. This made researchers conclude that the likely effects of early exposure to diet soda might be specific for boys. Overall, between 24% and 30% of mothers reported using low-calorie sweeteners, diet sodas or other diet beverages during pregnancy.
“Compared with male controls, males with autism in our study had more than tripled odds of having been exposed daily—gestationally and/or through breastfeeding—to either diet soda itself or comparable doses of aspartame from multiple sources. These exposure odds were the highest among cases with non-regressive autism,” the researchers concluded.
“These associations do not prove causality. Taken in concert, however, with previous findings of increased prematurity and cardiometabolic health impacts among infants and children exposed daily to diet beverages and/or aspartame during pregnancy, they raise new concerns about the potential neurological impacts, which need to be addressed.”
The study sheds light on the links between aspartame consumption during pregnancy and autism in children. However, it should be noted that the study design does not allow any cause-and-effect conclusions to be derived from the data. Additionally, data on aspartame-sweetened products was based on participants’ reported memories from years ago. Studies directly tracking the consumption of such beverages in mothers during pregnancy might produce different results.
The paper, “Daily Early-Life Exposures to Diet Soda and Aspartame Are Associated with Autism in Males: A Case-Control Study”, was authored by Sharon Parten Fowler, David Gimeno Ruiz de Porras, Michael D. Swartz, Paula Stigler Granados, Lynne Parsons Heilbrun, and Raymond F. Palmer.
