Tuesday, 6 November 2012

Bone density, vitamin D and autism

The quite recent paper published by Ann Neumeyer and colleagues* on bone mineral density in boys diagnosed with an autism spectrum disorder (ASD) brings me back to a topic which I've talked a little about before specifically with relation to use of a casein-free diet and what that may mean for bone health and autism.
Bones: I'm a Doctor not a ..... @ Wikipedia  

In that previous post the issue of bone health was discussed following a piece of research published by Hediger and colleagues** which indicated that bone development might be an important variable worth monitoring in cases of autism and indeed, issues with bone development might need to be listed as a potential adverse side-effect when a casein (milk) free diet is implemented.

Given my research interest in such dietary intervention(s), I'm always quite attentive to this area of investigation and the implications of any findings.

Without further ado, a few pointers from the Neumeyer paper:

  • This was a study of bone mineral density (BMD) as opposed to cortical bone thickness previously looked at by Hediger et al.
  • Eighteen boys diagnosed with DSM-IV autism (and confirmed ADOS ASD), with age-appropriate body mass index (BMI) not on any bone metabolism affecting medication and without gastrointestinal (GI) disease comorbidity known to affect bone health (Crohn's disease, coeliac disease) were compared against an asymptomatic control group of boys (n=19).
  • Various measures of BMD were taken alongside a salivary cortisol sample and fasting serum samples of vitamin D [25(OH)D], calcium, phosphorus and testosterone among other things. A 3-day food record and a measure of typical exercise activity were also completed.
  • Results: BMD at various sites of the body were significantly lower in the boys with ASD compared with controls. Indeed from the sites examined (lumbar spine, total hip) all showed mean reductions in BMD compared to controls, some even when results were adjusted for bone age and BMI.
  • When looking at food intake and bearing in mind that six of the ASD boys were following a gluten- casein-free diet either in single or combinatorially, the authors report that total caloric intake and intake of specific nutrients "did not differ between the groups". Well, actually they did but only when it came to vitamin D intake and lactose intake (lactose being the sugar from milk and dairy products and having previously been mentioned with autism in mind).
  • Physical activity was reported to be lower in the boys with ASD compared with controls, as measured by the percentage of both groups described as sedentary or low activity.
  • All other measures including serum calcium levels and testosterone were not significantly different from controls (indeed mean calcium levels were if anything slightly higher in the ASD group over controls, 9.7 mg/dl vs. 9.6 mg/dl respectively).


Bearing in mind the relatively small participant groups included in this study, there are a few preliminary conclusions which can be drawn based on the multiple levels of data presented, assuming a need for replication.

Quite interestingly was the notion that although BMD was significantly lower in the boys with autism, dietary intake in terms of calories and nutrients, whether on or not on a gluten- and casein-free diet (GFCF) did not seem to be the over-arching reason for the BMD issues identified. Yes, total calcium intake from both food and supplements combined was lower in the ASD group but this was not reflected in the serum calcium levels as presented functionally and allowing for the grouping of results.

Vitamin D by contrast was an important variable between the groups, with not only dietary intake significantly less in the ASD group but also functional serum levels lower and a greater proportion of the ASD group falling below the limits of suitable vitamin D levels. For those who don't know, vitamin D is an important requirement for the proper absorption of calcium. I know the authors talk about the vitamin D content of milk within the context of use of a casein-free diet, but actually even the UK Dairy Council report "there is very little vitamin D in milk and in fact only trace amounts and in the UK milk is not fortified with vitamin D". I appreciate that fortification might be different in other countries, but even then you would need to drink at least three servings of milk per day to get your vitamin D. There are also quite a few other better dietary sources of vitamin D also to consider.

Exercise levels were different between the groups. Even outside of the whole activity thing in relation to bone health, exercise one would assume, correlates with things like being outdoors and hence taking in a few rays (assuming you don't live in the same latitude of  the world as I do). Remember also this was a study of boys aged 8-14 years of age, so most exercise probably did not involve pumping iron indoors at the gym or anything like that.

So where next? Well I'd imagine that these results mean we need to start focusing a little more on things like vitamin D and physical activity levels in cases of autism. Vitamin D is something I've talked about on quite a few occasions with autism in mind as per other research on the sunshine vitamin and  the quite recent Saudi-Egyptian results. As was my opinion in that post, we perhaps need to take quite a wide-angled approach to vitamin D in terms of not just intake, but things like vitamin D receptor functioning, synthesis being linked to cholesterol and here I go again, the potential relationship with intestinal hyperpermeability (leaky gut) too. I'm sure that there are other factors to consider also.

By saying all this I'm not trying to detract from the BMD findings and their potential implications. Nor am I downplaying the need for appropriate dietetic support as and when exclusion diets are implemented in cases of autism or any other condition (for which I offer no endorsement). Merely that the relationship between diet, physical health and possibly mental health is probably going to be a complex one and one shouldn't assume anything otherwise.

I've probably said enough, or indeed too much, in this post so I'll leave it at that. To close, the apostrophe is being discussed in my house quite a bit at the moment, so here's a little ditty to help remember what it does courtesy of Wordy:

"I'm an apostrophe, 
come and take a look at me, 
I'm not a comma, 
I'm not a full stop, 
don't put me on the line - 
I go at the top!"


And I wonder if any remembers this mini-series....

----------

* Neumeyer AM. et al. Bone density in peripubertal boys with autism spectrum disorders. J Autism Dev Disord. November 2012.

** Hediger ML. et al. Reduced bone cortical thickness in boys with autism or autism spectrum disorder. J Autism Dev Disord. 2008; 38: 848-856.

----------

ResearchBlogging.org Neumeyer AM, Gates A, Ferrone C, Lee H, & Misra M (2012). Bone Density in Peripubertal Boys with Autism Spectrum Disorders. Journal of autism and developmental disorders PMID: 23124396