Food and Behaviour Research

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Soy Infant Formula and Seizures in Children with Autism: A Retrospective Study

Westmark CJ (2014) PLoS ONE 9(3): e80488. doi:10.1371/journal.pone.0080488   

Web URL: View this and related abstracts via Pubmed here. Free full text of this article is available online.


Seizures are a common phenotype in many neurodevelopmental disorders including fragile X syndrome, Down syndrome and autism. We hypothesized that phytoestrogens in soy-based infant formula were contributing to lower seizure threshold in these disorders.

Herein, we evaluated the dependence of seizure incidence on infant formula in a population of autistic children. Medical record data were obtained on 1,949 autistic children from the SFARI Simplex Collection. An autism diagnosis was determined by scores on the ADI-R and ADOS exams. The database included data on infant formula use, seizure incidence, the specific type of seizure exhibited and IQ.

Soy-based formula was utilized in 17.5% of the study population. Females comprised 13.4% of the subjects. There was a 2.6-fold higher rate of febrile seizures [4.2% versus 1.6%, OR = 2.6, 95% CI = 1.3-5.3], a 2.1-fold higher rate of epilepsy comorbidity [3.6% versus 1.7%, OR = 2.2, 95% CI = 1.1-4.7] and a 4-fold higher rate of simple partial seizures [1.2% versus 0.3%, OR = 4.8, 95% CI = 1.0-23] in the autistic children fed soy-based formula. No statistically significant associations were found with other outcomes including: IQ, age of seizure onset, infantile spasms and atonic, generalized tonic clonic, absence and complex partial seizures.

Limitations of the study included: infant formula and seizure data were based on parental recall, there were significantly less female subjects, and there was lack of data regarding critical confounders such as the reasons the subjects used soy formula, age at which soy formula was initiated and the length of time on soy formula.

Despite these limitations, our results suggest that the use of soy-based infant formula may be associated with febrile seizures in both genders and with a diagnosis of epilepsy in males in autistic children. Given the lack of data on critical confounders and the retrospective nature of the study, a prospective study is required to confirm the association.


Soy protein has now replaced animal protein in a wide array of foods, and infant formula containing soy instead of milk protein is commonly used for instants with actual or suspected allergies or intolerances, which includes many infants on the autistic spectrum.

Gluten-free, casein-free diets - as followed by many individuals with autism - are also likely to contain disproportionate amounts of soy protein to make up for the exclusion of the main proteins from grain and milk.

The findings of this study are therefore potentially very important, especially given the high prevalence of epileptic seizures in people with autism.

This study was retrospective, and involved looking only for associations, so it can not address causality.  However, it was inspired by an earlier observation by the author that in mice, changing the protein source in their diets from soy to milk protein led to a 50% reduction in seizures - comparable to the effects of anti-convulsant medications.

The author speculates that the high phyto-oestrogen content of soy protein might reduce seizure thresholds.  That possibility - and these findings - clearly warrant further urgent investigation.

For an accessible summary of the main findings, see the associated news release from the University of Wisconsin-Madison:

Study suggests potential association between soy formula and seizures in children with autism