|..but in my game, I'm the bad guy,
and I live in the garbage.
I wouldn't say that I'm an advocate for everything implied by the correlations being made between vitamin D levels and autism given that vitamin D levels have also been linked to everything from depression (see here) to schizophrenia (see here), issues which might also show some passing connection for some people on the autism spectrum (see here for example). But I am interested in how this research area is evolving...
And evolving it is, as yet another study has been published on vitamin D and autism, this time from Elisabeth Fernell and colleagues  (open-access) based at the University of Gothenburg in Sweden. Examining 25-hydroxyvitamin D (25(OH)D) levels in dried blood spots "taken in the neonatal period for metabolic screening", researchers concluded that: "low prenatal vitamin D may act as a risk factor for ASD [autism spectrum disorder]."
Aside from some happiness that the fantastic resource which is the neonatal blood spot is being put to good scientific use with autism in mind (see here), I was particularly interested to read about the findings from this research group given their previous foray in this area (see here) based on the paper from Kočovská and colleagues  (open-access). On that occasion they concluded that young adults diagnosed with an ASD were, as a group, quite a bit more likely to present with lower vitamin D levels than siblings, parents and an asymptomatic control group.
Back to the Fernell paper, and a few pointers might be in order:
- "The aim of the present study was to address the emerging hypothesis that low levels of vitamin D at birth increase the risk for ASD." OK.
- Sibling pairs were used, one child diagnosed with autism, the other "non-ASD affected". Participants were drawn from two samples, a Gothenburg catchment area sample and a "Stockholm Somali group" which have been previously used in a prevalence study of autism in Somali children in Sweden (see here). Those in the know about autism research will perhaps have heard about autism and Somali children a few times before (see here).
- Participants were coded according to ethnicity into one of three groups: Swedish, Miscellaneous (non-Scandinavian Europe, South America and East Asia) and African/Middle East. This was due to: "well-known ethnic disparity of vitamin D status."
- Results: "Children to parents of non-Scandinavian ethnicities had lower mean 25(OH)D levels than children to Swedish parents." See the previous point.
- "The mean 25(OH)D level was lower in children with ASD... than in their siblings." This trend was significant in "the Swedish and Miscellaneous groups, but not in the African/Middle East group." The authors report that season of birth, a potentially important factor in birth vitamin D levels was likely not the primary variable to account for the ASD - non-ASD sibling differences but there were some disparities noted. I would also draw your attention to another comment from the authors: "Since we studied newborn children before diagnosis, our results are definitely unrelated to lifestyle and diet of the individual, although the mother’s lifestyle and other environmental factors cannot be ruled out."
- Author conclusion: their findings may support: "the hypothesis that developmental vitamin D deficiency during late pregnancy may carry an increased risk of ASD in the child." Alongside, that is, the requirement for further research with larger numbers of participants.
I would certainly echo the sentiments of the authors for the need for larger-scales studies of any connection between low pregnancy/birth vitamin D levels and risk of autism. This is however not the first time that this issue has been studied as per my commentary on the results from Whitehouse and colleagues  (see here) who based on the use of the Autism-Spectrum Quotient (AQ) (itself the topic of some recent inquiry) concluded that: "Maternal 25(OH)-vitamin D concentrations were unrelated to offspring scores on the majority of scales" bearing in mind their focus on mums not offspring when assaying for vitamin D.
A few further points before I let you go about your business.
"In this study we did not examine other possible causes for ASD, such as for instance infections during pregnancy." A very important point indeed if one looks at some of the research literature in this area (see here).
"Autoimmunity is another possible cause for ASD, which was not investigated. However, as low vitamin D is suggested to contribute to the pathogenesis of autoimmunity... our findings could be relevant in this context as well." Again, another potentially important point raised here on the basis of other research which has brought the issue of autoimmunity into the autism-vitamin D frame (see here). More generally, the issue of autoimmunity and autism is of increasing research interest.
Finally, the authors leave us with a tantalising question: "whether or not adequate supplementation of vitamin D to pregnant women might lower the risk for ASD in the offspring"? Before anyone get's ahead of themselves, I think we need quite a bit more discussion and study on this question specific to autism given that more generally vitamin D for pregnant women is seemingly being more frequently indicated.
Just one more thing (to coin a phrase)... although no-one really knows the specific hows, whys and wherefores of any vitamin D connection to autism, I'd be minded to suggest that physiological issues such as gut permeability (yes, it is a real thing) might also register on any future research endeavours given data like that from Assa and colleagues  adding to an already interesting area (see here). I'm not saying that this is the only potential factor but one among many.
Music: Do you feel lucky punk?
 Fernell E. et al. Autism spectrum disorder and low vitamin D at birth: a sibling control study. Molecular Autism. 2015; 6: 3.
 Kočovská E. et al. Vitamin D in the General Population of Young Adults with Autism in the Faroe Islands. J Autism Dev Disord. 2014 Jun 14.
 Whitehouse AJ. et al. Maternal vitamin D levels and the autism phenotype among offspring. J Autism Dev Disord. 2013 Jul;43(7):1495-504.
 Assa A. et al. Vitamin D Deficiency Predisposes to Adherent-invasive Escherichia coli-induced Barrier Dysfunction and Experimental Colonic Injury. Inflamm Bowel Dis. 2015 Jan 14.
Elisabeth Fernell, Susanne Bejerot, Joakim Westerlund, Carmela Miniscalco, Henry Simila, Darryl Eyles, Christopher Gillberg, & Mats B Humble (2015). Autism spectrum disorder and low vitamin D at birth: a sibling control study. Molecular Autism : 10.1186/2040-2392-6-3