In a groundbreaking new discovery, researchers in Sweden have discovered that children who later develop Autism Spectrum Disorder (ASD) have lower vitamin D levels at birth than their typically developing siblings do.
This helps rules out, but doesn’t disprove, environmental factors as a cause of lower 25(OH)D levels in ASD children and suggests some form of heritability as the cause of the lower 25(OH)D levels. Vitamin D levels at birth are dependent on the mother’s vitamin D levels. Although this study suggests heritability of 25(OH)D, it is possible that the mothers either took less vitamin D in foods and supplements or got less sun exposure when they were pregnant with the ASD sibling.
They studied a total of 58 pairs of siblings, each pair consisting of one child with ASD and one typically developing child. In their study, they had 28 pairs where the mother were of Swedish origin, 12 pairs with miscellaneous maternal origin and 18 pairs with African or Middle Eastern mothers.
The authors clearly address the Center for Disease Control’s repeated contention that skin color has no effect on ASD by citing a recent large population-based study in Los Angeles published in the journal Pediatrics, which clearly showed ASD is more common among dark-skinned individuals.
In the Swedish study, the authors found the following 25(OH)D levels at birth for the different maternal nationalities:
Mother’s nationality ASD Normal P value
Swedish (28) 14 ng/ml 19 ng/ml 0.042
Miscellaneous (12) 9 ng/ml 12 ng/ml 0.015
African/Middle East (18) 3 ng/ml 4 ng/ml 0.68
Many of the African and Middle Eastern children had 25(OH)D levels around the lower limit of detection. Differences in season of birth did not account for the differences.
The authors concluded:
“Although low levels of vitamin D could have a genetic origin and as such be associated with ASD, our study is the first to rule out ASD-related lifestyle mechanisms as explanation for low 25(OH)D levels, since the samples were taken in the newborn period. Future research should include a larger cohort followed prospectively and also study whether or not adequate supplementation of vitamin D to pregnant women might lower the risk for ASD in the offspring.”
So far, no vitamin D-related gene has been identified in the search for a genetic cause of ASD. However, as I write in my upcoming book, a qualitative genetic defect is not needed to explain the low 25(OH)D levels ASD children inherit. All that is needed is a quantitative effect to explain the heritability of 25(OH)D levels. When a quantitatively low fetal 25(OH)D level interacts with a genetic predisposition for ASD, the child develops ASD unless the mother and/or infant is given adequate doses of vitamin D or sunshine.
The researchers hypothesize that increasing the 25(OH)D levels of mothers should help prevent the genetic predisposition for ASD from expressing itself as the ASD phenotype. I agree, however, I believe some of that gene/environmental interaction occurs during toddlerhood, which is when most cases of ASD present.
As I note in my book, most toddlers do not have a reliable and significant source of vitamin D. In the USA, ninety percent of toddlers don’t take vitamin D supplements, they get little or no unprotected sun exposure, they are now weaned on fruit juice instead of vitamin D-enriched milk, and they get no significant amounts of vitamin D in their diet. It is no wonder that ASD first becomes apparent in toddlerhood.
An easily conducted study to test the vitamin D hypothesis is to simply ask a cohort of parents of ASD children if they administered the American Academy of Pediatrics recommended daily dose of 400 IU/day of vitamin D, weaned on vitamin D-enriched cow’s milk and/or allowed unprotected sun exposure when their child with ASD was an infant and/or toddler. Then compare the parents’ answers in the ASD cohort to the answers from the parents of typically developing children.
The current Swedish study is groundbreaking. However, I don’t know how scientists would do a randomized controlled trial (RCT) of vitamin D to see if it prevents ASD. Perhaps a RCT that included a placebo group of mothers who took the recommended 400 IU/day and compare them to mothers who take 6,000 IU/day; perhaps an ethics committee would allow such a study. However, such a committee would not allow a RCT in which placebo toddlers went without any vitamin D supplementation, as parents allow now.
Elisabeth Fernell, Susanne Bejerot, Joakim Westerlund, Carmela Miniscalco, Henry Simila,Darryl Eyles, Christopher Gillberg and Mats B Humble. Autism spectrum disorder and low vitamin D at birth: a sibling control study. Molecular Autism 2015, 6:3 doi:10.1186/2040-2392-6-3. Published: 14 January 2015.