Tuesday, 20 September 2016

First trimester maternal vitamin D status and offspring autism risk?

Vitamin D - the sunshine vitamin/hormone - is seemingly everywhere these days in research terms. At the time of writing this post we have news that vitamin D might cut the risk of severe asthma attacks if taken alongside prescribed asthma medication. The week before that it was the suggestion that vitamin D might be part of the explanation as to why childhood learning difficulties were more commonly found in children conceived during the winter months. Vitamin D is seemingly shouldering quite a bit of responsibility when it comes to health and wellbeing.

Today I'm adding to that research responsibility by introducing the paper by Jianzhang Chen and colleagues [1] who suggested that: "Lower first trimester maternal serum levels of 25(OH) D were associated with increased risk of developing autism in offspring." 25(OH)D by the way, is calcifediol, and refers to the typical metabolite assayed for to provide a measure of ones vitamin D status.

Chen and colleagues accessed archived maternal blood samples taken during the first trimester of pregnancy - "11–13 weeks gestational age" - for some "68 children diagnosed with ASD [autism spectrum disorder] and 68 sex and age matched typically-developing children." Not only was vitamin D status examined in those samples but various other potentially useful metabolites: "unmetabolized folic acid (FA), vitamin B12, homocysteine (HCY) and High Sensitivity C Reactive protein (CRP)" that may have some important autism-related links for some (see here and see here for example).

Their report on this occasion focused on the vitamin D results and the finding that mums of children diagnosed with autism/ASD were as a group more likely to present with lower levels of 25(OH)D than control (not-autism) mums. Indeed, when it came to the percentages of who were and weren't vitamin D deficient, some 55% of mums with a child with autism fell into this category compared with less than 30% of control mums. I might add that vitamin D deficiency is typically only one 'banding' when it comes to looking at vitamin D status. With the caveats that this was a study of maternal vitamin D and autism offspring risk in China (so not necessarily translatable to other parts of the world; see discussions shortly) authors also observed a possible correlation between maternal vitamin D status and autism 'severity' in their cohort.

Bearing in mind my recent discussions on the maternal body as 'an environment in autism science' (see here) and the potential pitfalls this presents, the data from Chen et al are interesting. Accepting also that I have a bit of a research 'thing' for vitamin D when it comes to autism on this blog (see here and see here for examples), this work seemingly fits in pretty well with the idea that nutritional factors at critical periods may indeed play a role in the development of at least some autism. Indeed, when one talks about season of conception as potentially being associated with offspring risk of behavioural or developmental issues [2], vitamin D levels look like an attractive research target. The next stage in this research process would be independent replication and perhaps, looking at other populations too.

In fact, on the topic of other populations similarly studied with maternal vitamin D status and offspring autism or autistic traits in mind, the research path previously trodden might not be all one-way. Take for example research coming out of Australia [3] a few years back that observed little in the way of connection between maternal vitamin D levels and offspring development (see here). OK, they used the Autism Spectrum Quotient (AQ) as their behavioural diagnoser (something that might not be cutting the appropriate mustard in recent times) but all-in-all they found little in the way of any relationship in contrast to the Chen findings. The fact that the Raine study data used in the Australian paper also included quite a few more participants also offers a significant advantage to the smaller Chen study.

But I don't think we can just discount the Chen results as they stand, as more and more vitamin D is thrust onto the [autism] research stage. Combined with the recent guidance from the Government here in Blighty suggesting that vitamin D supplementation perhaps needs to be a lot more widespread than it is (see here and see here) throughout the population as a whole, research opportunities aplenty present themselves in this area of growing importance...

Oh, and that includes with regards to the genetics of vitamin D metabolism too (see here).

To close, if you are easily offended by bad language, please stay away from this advert for a cookbook (probably not the language you're likely to hear on Bake Off whatever channel it's on).

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[1] Chen J. et al. Lower maternal serum 25(OH) D in first trimester associated with higher autism risk in Chinese offspring. Journal of Psychosomatic Research. 2016; 89: 98-101.

[2] Zerbo O. et al. Month of conception and risk of autism. Epidemiology. 2011 Jul;22(4):469-75.

[3] Whitehouse AJ. et al. Maternal vitamin D levels and the autism phenotype among offspring. J Autism Dev Disord. 2013 Jul;43(7):1495-504.

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ResearchBlogging.org Chen, J., Xin, K., Wei, J., Zhang, K., & Xiao, H. (2016). Lower maternal serum 25(OH) D in first trimester associated with higher autism risk in Chinese offspring Journal of Psychosomatic Research, 89, 98-101 DOI: 10.1016/j.jpsychores.2016.08.013