Effects of pregnancy vitamin D deficiency on social behaviours of offspring rats

I note the findings reported by Nathanael Yates and colleagues [1] have garnered a few lay and science media headlines recently (see here) as authors concluded that "early life levels of vitamin D are an important consideration for maternal behavioural adaptations as well as offspring neuropsychiatry." Further coverage of their findings is provided in a helpful article for The Conversation (see here), where some authors - including the autism research powerhouse that is Andrew Whitehouse - provide a little more interpretation of their findings. I might also add that Whitehouse is no stranger to the vitamin D - autism research story (see here).

So, what's all the current discussion about?

Well, vitamin D - the 'sunshine' vitamin/hormone - is front and centre of this latest research, and some investigation into "how early life vitamin D deficiency during rat pregnancy and lactation alters maternal care and influences neurodevelopment and affective, cognitive and social behaviours in male adult offspring." This is set within the context that vitamin D seems to be doing a lot more than just contributing to bone health (see here). You'll of course note the use of the word 'rat' in the above text, and in particular what happened to offspring baby rats in terms of "offspring neurodevelopmental markers, ultrasonic vocalisations and adult behavioural outcomes including social, cognitive and affective-like behaviours" when mummy rat diets are loaded up with enough vitamin D as opposed to those mummy rats who were provided with a vitamin D deficient diet. The theory behind those vitamin D loaded vs. vitamin D deficient mummy rat diets is that: "In both humans and rats, a baby developing in the womb is completely reliant on the mother’s vitamin D stores." Probably something to do with the lack of sunlight exposure in the womb(!)...

Results: there did seem to be some difference across various 'test a rat / test an offspring rat' measures as a function of vitamin D status, looking across behaviour, brain scans (yes, rats did meet some MRI equipment) and also "plasma corticosterone levels and neural expression of genes associated with language, dopamine and glucocorticoid exposure." So for example, authors describe how "males that had been exposed to vitamin D deficiency in early life exhibited decreased social behaviour, impaired learning and memory outcomes and increased grooming behaviour, but unaltered affective behaviours." It's not difficult to see the 'decreased social behaviour' links that *could* be made with a condition / label / diagnosis like autism; particularly when vitamin D has quite the peer-reviewed research history with autism in mind (see here).

Interestingly too, but not made too much of in the chatter about this study for obvious reasons, were the observations made around maternal care as a function of vitamin D status, bearing in mind that vitamin D deficiency will probably impact both mummy rat and baby rat. So: "the quality of maternal care was decreased in dams consuming a vitamin D-deficient diet." Mmm...

Whilst this is important work, and adds to our understanding that appropriate nutrition throughout the lifespan is important to various aspects of functioning, I'll reiterate that this was research using rats. Rats not humans. It is perhaps timely that at around the same time that the Yates paper was published, I also chanced upon some discussion over at Spectrum on how we all need to be a little bit careful when talking about modelling autism in various animals (see here) and their relevance to real, often much more complicated, people (see here) and their [multiple] labels (see here).

I note that in their piece for the The Conversation, authors caution that their findings don't mean everyone who is pregnant (or could become pregnant) should rush out and load up on vitamin D so as to potentially influence offspring developmental course. I would second that view; but would also direct your attention to some Government advice quite recently (at least here in Blighty) that we should perhaps all be thinking about vitamin D supplementation (see here) and the many and varied ways that this vitamin/hormone *might* impact on our physiology and beyond (see here).

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[1] Yates NJ. et al. Vitamin D is crucial for maternal care and offspring social behaviour in rats. J Endocrinol. 2018 May;237(2):73-85.

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