Vitamin D and Autism
If you search the web for pages linking autism and vitamin D, most of the articles you will find (as of early 2011) are discussing Dr. John Cannell's paper, Autism and Vitamin D, published October 8, 2007 on-line in Medical Hypotheses. In the article, Dr. Cannell presents his original theory that the rising incidence of autism is due to the relatively recent trend toward sun avoidance, and the resulting drop in vitamin D3 levels, particularly in babies and young children.
Added in March, 2013: While what I wrote above was true in 2011, it no longer is today. Now, if you search "vitamin d and autism" you will find references to recent studies, and to far more sites that discuss a potential link between autism and a vitamin D3 deficiency. How quickly things change, or maybe I should say, "How fast information spreads these days." Note also that a search on "vitamin d and dyslexia" brings Vitamin D and Dyslexia from this OnTrack Reading website as the top result (as of late 2013 anyway.) That too will change, I suspect, once the many parallels (discussed below) between autism and dyslexia are investigated further.
As of early 2011, many websites discussing "Vitamin D and Autism" were relying upon Dr. Cannell's theory Scientific American magazine, in 2008, also published an article hypothesizing a possible link between autism and a vitamin D deficiency. Unfortunately, the author of that article failed to credit Dr. Cannell for originally formulating and publishing the theory. (If you read it, note that at least they allowed him the privilege of adding the first comment.)
Clearly then, the attempt to link a vitamin D deficiency to autism is a recent development. My suggestion that there might also be a link between a vitamin D deficiency and dyslexia is an even more recent development, since it was Dr. Cannell's paper that got me thinking about it. Of course, someone I'm unaware of might have proposed similar linkages much earlier.
A Parsimonious Theory - The Simplest Explanation Is Often the Best
In his paper, Dr. Cannell explains how the spread of autism, including the specific populations most affected, are explained by his vitamin D theory. He also explains how common symptoms, including how widely they vary, are covered in his theory. And finally, he explains how most of the other suspected causes of autism, such as mercury contamination or oxidative stress, are also subsumed by his theory. In short, he has come up with a parsimonious theory of autism, a simple explanation that explains all facets of the epidemic.
Important Note to Parents of an Autistic Child: Please read this exchange between Dr. Cannell and a parent of an autistic child, from the VitaminDCouncil Newsletter Archives, Jan 2010. Also see this update from a mother of three autistic children, from the Dec 2010 newsletter. (When you get to the page, click on the December Newsletter, titled More Autism Reports, to open the PDF.)
I'll leave it to you to read his paper if you're interested; it's not all that technical so it's a fairly easy read. My reason for discussing it here is to show any linkages between autism and dyslexia, for if the links are strong then it's also likely that if his theory is eventually proven correct it will strengthen my hypothesis that dyslexia is also a result of a vitamin D deficiency. I'll start first with a comparison of the trends in autism versus dyslexia, drawing on the factual information about autism in Dr. Cannell's paper.
Fact: Autism Cases Have Increased Rapidly Over the Past 20 Years
Dyslexia is generally thought to affect around 10% of the population, more or less, and I know of no study that indicates that it is increasing over time. Perhaps long-term educators in the lower grades have strong feelings on this, but as of now I can't see a linkage between autism and dyslexia in this regard. If a vitamin D deficiency underlies dyslexia, the rate should have been increasing significantly over the past 15 years or so, but I'm unaware of such an increase.
Fact: Autism has Genetic Underpinnings
This one is similar for dyslexia. Just as autism runs in families, so does dylexia and there is plenty of research backing for both. If it turns out that the same gene or combination of genes are involved then it would seem more likely that Dr. Cannell's theory would also apply to dyslexia.
Fact: Autism is a Developmental Disability
Dyslexia too is considered a developmental disability. Many studies have been done showing delays in development across various skills including speech, fine motor, vision, etc. As is the case with autism, there is a wide range of outcomes.
As both conditions appear to be neurological disorders, with many of the same skills affected, it seems likely that if a vitamin D deficiency is causing the neurological problems in an autistic child then it could also be causing similar disorders in a dyslexic child.
Fact: Autism is an Idiopathic Disease
All "idiopathic" means is that there is no known cause. This is true of the majority, though not all, autistic individuals. Similarly, dyslexia is a condition that has gone unexplained, although as with autism, many associations have been found. The issue is whether any of those associations are causal, or if they are also the result of a yet-unexplained common underlying cause.
So here we have two conditions, both neurological disorders of unknown origin. If one is turns out to be caused by a vitamin D deficiency, will the other also?
Fact: Autism Affects Four Times More Boys Than Girls
Teachers refer more than twice as many boys as girls for reading problems though it's unclear whether some of those referrals might be for behavioral issues instead. Studies do show that more boys are dyslexic than girls, but not by a four-to-one ratio.
Nevertheless, if Dr. Cannell is correct in saying that estrogen improves the functioning of vitamin D3 in the system, whereas testosterone has no impact, and if dyslexia is impacted by a vitamin D deficiency as well, you would then expect that more boys would be dyslexic than girls.
Fact: Autistic-like Symptoms are Related to Low Maternal Fish Consumption
From Dr. Cannell's paper: "...low maternal seafood consumption was associated with infants with an increased-risk of lower verbal IQs and poor outcomes for social behaviors, fine motor skills, communication, and social development—outcomes eerily similar to autism." He states that it's not known whether it was due to the vitamin D3 in the fish or the Omega 3's or something else, but there was an association found.
Similarly, studies of poor readers have shown that fish oil or a multi-vitamin are both associated with an increase in word identification ability. Both studies are discussed later in this section.
Fact: Autism is More Common Farther from the Equator
More generally, the less sun a geographic area receives, the higher the incidence of autism. I'm not aware of any similar studies regarding the distribution of dyslexia, so this one is an open question. Are there more dyslexics as one goes north, or into areas that receive diminished sun due to smog or persistent cloud cover?
Fact: African-Americans, Particularly in Northern Latitudes, are More Likely to be Autistic
The higher melanin concentration in dark skin prevents blacks who have moved to more northern climates from absorbing the amount of sunlight they need to create sufficient vitamin D3 stores. The result is that blacks in northern climates are much more likely to be vitamin D3 deficient than are lighter-skinned people. And rates of autism are much higher for blacks than for other races.
Is this also true of dyslexia? I'm not sure. Certainly the school performance of black children in center city schools is subpar on average, but so many variables come into play that it would be nonsense to claim on that basis that a higher percentage of blacks are dyslexic. If your school is so poorly run that most of the children attending have low reading scores, certainly instructional methods and the education environment must play a major role in outcomes.
You can see that dyslexia parallels autism in many respects, but that there are open questions in some areas. I'm hoping that readers who are aware of studies that attempt to answer some of these questions, or even those of you with extensive first-hand experience, will contact me and let me know of those studies, orParallels between autism and dyslexia certainly exist, but open questions remain relate your experiences so that some of these questions can be answered. For example, is dyslexia increasing along with autism? Is dyslexia more prevalent in northern latitudes? Are black children more likely to be dyslexic?
My purpose here was simply to show that there are several parallels between autism and dyslexia. These common aspects add support to my hypothesis that dyslexia and autism both fall on the same spectrum of disease, with dyslexia a milder manifestation of a condition of developmental delay or even maldevelopment. If true, and if Dr. Cannell's vitamin D theory of autism is borne out by future research, it stands to reason that his theory could also apply to the dyslexic population as well.