Hand holding up Vitamin D3 pill in sunlight

Returning now to the hypothesis I stated in Diet and Dyslexia regarding a possible relationship between dyslexia and a vitamin D deficit:

Hypothesis: ADHD, dyslexia, Asperger's and autism are all associated conditions that have in common a failure of a child to develop normal childhood skills on schedule. What distinguishes them is the severity of the deficit in development, with the ADHD child eventually developing into a more or less normal adult while the autistic child might never develop the skills needed to be considered a fully functioning adult. Dyslexia and Asperger's fall between those two extremes. These delays in development are due to genetic tendencies that are triggered by a vitamin D deficiency. Another such trigger could be a deficiency in Omega-3's.

Could a Vitamin D Deficiency Cause Dyslexia?

Let me explain how I arrived at the point where it occurred to me to ask the above question. In 2008, I was already familiar with vitamin D3 as I was taking it myself and had been tested to ensure that I was getting what I feel is the right amount for our Wisconsin winters. Over the course of a year or so I read a lot about the effects of vitamin D3 on health. Then one day I read a brief note linking a vitamin D deficiency to autism. This led me to Dr. John Cannell's paper titled Vitamin D Theory of Autism, a paper I'll discuss in some detail later. I should also emphasize out that Dr. Cannell was publishing a theory, not a research finding.

Extending a vitamin D theory of autism to include dyslexia

ADHD, dyslexia, Asperger's, and autism are all conditions that are diagnosed from symptoms lists. Those symptoms lists have considerable overlap and most of them concern maldevelopment or delayed development in various areas, both physical and mental. It seems reasonable, then, to consider each of these conditions to be part of a spectrum of delayed or arrested development. As the symptoms become more severe, the diagnosis moves up the scale from ADHD all the way to autism.

Once I decided that Dr. Cannell's hypothesis linking a vitamin D deficiency to autism was probably correct, it was logical to wonder if dyslexia was also a condition linked to that same vitamin D deficiency. My reasons for wondering that include:

  • Dyslexia tends to run in families, as does autism.
  • Dyslexic children often exhibit developmental delays in motor skills as do autistic children.
  • Many of the symptoms of dyslexia overlap the symptoms of ADHD, Asperger's and autism.
  • Children diagnosed with ADHD, Asperger's and autism often also struggle with reading
  • Increased consumption of fish has been shown to help both autism and reading ability.
  • Dyslexia and autism both affect more boys than girls.

That said, a decade after Dr. Cannell proposed a link between autism and a vitamin D deficiency, much has come out in support of his theory. But in the decade or more since I speculated that a similar link between dyslexia and vitamin D might exist, virtually nothing has come out in direct support of my hypothesis that vitamin D is linked also to dyslexia.

So, What's a Parent of a Dyslexic Child to Do?

Based on what I've said above, it's hard to make a solid case that vitamin D3 supplementation (either by sun exposure or with supplements) will address dyslexia. All I've done over that time is to keep an open mind on a link between dyslexia and a vitamin D deficiency. So far I've seen no direct refutation of the idea and I remain hopeful that it's at least part of the answer.

Even if dyslexia is not related to a vitamin D deficiency, parents should consider the other potential health benefits of vitamin D3

Nevertheless, whether dyslexia is affected or not by vitamin D3, so many other health issues have been related to a vitamin D deficiency that a parent would be foolish not to at least consider getting the entire family's D3 levels into the range recommended by the many researchers into the topic, that being a level of 40-60 ng/ml. Some want an even higher level to be reached, but they all agree on maintaining at least 40 ng/ml and they tend to also agree that 60 ng/ml is not too high.

I find it encouraging that Dr Cannell's theory appears to be being confirmed by studies indicating a possible link between autism and a vitamin D deficiency. After all, addressing such a deficiency is both easy to do and inexpensive. I also suspect that I'm correct in linking dyslexia and autism as diseases along a spectrum of delayed or arrested development.

Treatment Effect or Preventative Effect or Both?

Dr. Cannell's theory is aimed at prevention of autism, in that he hypothesizes that maintaining sufficient levels of vitamin D3 in both the mother during pregnancy and the child following birth and thereafter would prevent the onset of autism. He is less certain of a treatment effect. That is, he is less certain, but quite curious, whether a child already diagnosed with autism can be successfully treated with vitamin D3. He's certainly not willing to rule out the possibility.

In the case of dyslexia, I too am theorizing a preventative effect although, frankly, I doubt that will ever be adequately researched partly because dyslexia is just too poorly defined. I also share Dr. Cannell's optimism about a treatment effect, only in my case, a treatment of dyslexia rather than autism.

Reading is a learned activity so it's completely unrealistic to expect vitamin D3 to turn a poor reader into a good one, but it could make learning easier by removing obstacles

For now, I hope that we eventually find that some dyslexia symptoms are reduced or even eliminated, at least in younger children, when vitamin D3 levels are increased to sufficient levels. Of course, since reading is a learned activity it's completely unrealistic to expect vitamin D3 to turn a poor reader into a good one. What it could do, however, is remove some of the blocks that are making it difficult for your child to learn to read. Regardless, the message I've tried to convey here is that you should consider maintaining adequate vitamin D3 levels for much broader health reasons, even if my theory relating dyslexia and a vitamin D deficiency never proves out.

Should you decide to investigate Vitamin D further, Vitamin D3 Questions, has some useful information.