FAB: Gut microbiota differences seen in people with autism may be due to dietary preferences
This new study adds yet more evidence to what many previous research studies have already shown - which is that poor dietary habits, and particularly selective, restricted or 'picky eating', are unusually common in children on the autistic spectrum (as many parents and professionals have always known).
Rather more controversially, despite this study being purely correlational (and the fact that 'correlation is not causation') the researchers claim to have shown that
1) 'picky eating' is the primary cause of the gut microbial differences that have also been extensively reported in connection with autism and related conditions - and
2) their data rule out the idea that gut microbial imbalances could have any effect on ASD
This conclusion seems to go well beyond what the study data actually showed. A huge research literature now shows (pretty definitively) that gut-brain communications work in BOTH directions.
So yes - the highly restricted diets of many individuals with ASD would be expected to affect gut microbial balance (and not in a positive way). But in turn, an unhealthy balance of gut microbes can affect not only gut health, but also immune system regulation, and brain function.
ASD is associated with difficulties in all these areas - and research (including some human studies) shows that dietary interventions to improve gut microbial balance may have positive effects on behaviour in children with ASD, as well as reducing both gastro-intestinal and other symptoms. For example:
a recent randomised controlled trial (the gold standard study design for investigating causal effects) - did find at least preliminary evidence that probiotic supplementation vs placebo may be of benefit in some children with ASD.
Preliminary evidence of benefits has also been reported from open studies using faecal transplants to modify the gut microbiome - although again, more research is needed.
A major problem for research (and practice) is that the ASD diagnosis itself is extrenely broad and purely descriptive, so individual variability within ASD is huge. The 'causes' of this and other neurodevelopmental conditions (which all overlap) are also highly complex - involving both genetic and environmental factors, which interact constantly, and differ both between individuals, and over time.
These are literally 'developmental' conditions, and simplistic generalisations about their causes - let alone claims to have solved the 'chicken and egg' problem - make no sense when it comes to the role of the gut-microbial-brain axis in ASD.
By attracting attention to the very poor diets consumed by many individuals with ASD, this study could have important benefits - but only if this leads parents, professionals and researchers to find better ways to help improve the nutritional quality and balance of those diets.
And for further information please see:
< Gut bacteria don't cause autism. Autistic kids' microbiome differences are due to picky eating