Maternal dietary fat intake in association with autism spectrum disorders

Abstract

Our goal in this study was to determine whether maternal fat intake before or during pregnancy was associated with risk of autism spectrum disorder (ASD) in the offspring. Our primary analysis included 317 mothers who reported a child with ASD and 17,728 comparison mothers from the Nurses' Health Study II (index births in 1991-2007). Dietary information was collected prospectively through a validated food frequency questionnaire. Binomial regression was used to estimate crude and adjusted risk ratios. Maternal intake of linoleic acid was significantly inversely associated with ASD risk in offspring, corresponding to a 34% reduction in risk in the highest versus lowest quartiles of intake. Mothers in the lowest 5% of ω-3 fatty acid intake had a significant increase in offspring ASD risk as compared with the remaining distribution (risk ratio = 1.53, 95% confidence interval: 1.00, 2.32); this association was also seen in the subgroup of women (86 cases and 5,798 noncases) for whom dietary information during pregnancy was available (risk ratio = 2.42, 95% confidence interval: 1.19, 4.91). Thus, variations in intake of polyunsaturated fats within the range commonly observed among US women could affect fetal brain development and ASD risk. Because the number of women with diet assessed during pregnancy was small, however, these results should be interpreted cautiously.

Keywords: autism; dietary fat; linoleic acid; polyunsaturated fatty acids; ω-3 fatty acids; ω-6 fatty acids.

Figure 1.

Exclusions for the primary study group, which included 317 mothers who reported a child with autism spectrum disorder (ASD) and 17,728 comparison mothers from the Nurses' Health Study II. Parous women were those who had had a pregnancy lasting >6 months in 1991–2007. For women who answered the 2005 but not the 2009 questionnaire, only births through 2003 were included. Women who provided ASD information were those who returned the long version of the questionnaire in 2005 or 2009 and did not skip the ASD question. Child exclusion factors were as follows: missing year of birth (n = 51), indication that the child was adopted (n = 6), failure to confirm ASD in a nested case-control follow-up study (n = 6), or report of a competing diagnosis (Down syndrome, fragile X syndrome, trisomy 18) (n = 6); remaining individuals were excluded on the basis of not meeting the case definition because of reporting the diagnosis on only 1 questionnaire. Primary study group includes 317 cases; pregnancy subgroup includes 86 cases.

Figure 2.

Association of maternal dietary fats with risk of autism spectrum disorder in offspring, according to extreme deciles and 5% of intake, in mothers who reported a child with autism spectrum disorder and comparison mothers from the US Nurses' Health Study II (index births in 1991–2007). Risk ratios for the association between maternal dietary ω-3, α-linolenic acid, ω-6, and linoleic acid are shown. Error bars represent 95% confidence intervals. The first column of graphs shows high and low deciles of maternal intake compared with the referent middle 80% of the distribution in association with risk of ASD; the second column compares those in the highest 5% and lowest 5% of maternal intake to those in the remaining 90% of the distribution. Total polyunsaturated fat demonstrated similar associations as ω-6 fatty acids; other fats not shown for these analyses of deciles and extremes of intake did not exhibit significant associations.