"Many researchers now fear that the explosive increase in autism is a result of pregnant mothers having close to no vitamin D in their bodies and then young babies and infants being similarly shielded from the Sun. The Centers for Disease Control (CDC) says that virtually no infants are getting enough vitamin D. The inadequacy figures, even using the CDC's pre-2011 lower recommendations of what they thought the body should have, was that 90 percent of infants are deficient.The full article can be found here.
According to Cannell, the highest autism rates occur in areas that have the most clouds and rain, and hence the lowest blood levels of vitamin D. A Swedish study has strongly linked sunlight deprivation with autism. Moreover, blacks, whose vitamin D levels are half those found in whites living at the same latitudes, have twice the autism rates. Conversely, autism is virtually unknown in places such as sunny Somalia, where most people still spend most of their time outdoors. Yet another piece of anecdotal evidence is that autism is one of the very few afflictions that occur at higher rates among the wealthier and more educated - exactly the people most likely to be diligent about sunscreen and more inclined to keep their children indoors."
The author ensure he states this is anecdotal evidence, and nobody is attempting to present this as peer-reviewed science here, but clearly there is a need to continue to research this to determine if there is any merit. There has been some science which has been published regarding the rates of autism in various geographical areas and how areas with more clouds and rain tend to have higher rates, so perhaps there is something to this.
We obviously won't see scientists running out claiming that a lack of vitamin D causes autism anytime soon, because that isn't how real science works. That said, I would not be surprised to see studies that pursue this hypothesis even further than the existing research that has been published thus far. In fact, I wouldn't be surprised to learn that such studies are already underway.
I do question what the antivaxer response would be to this theory however as it somewhat puts them in a difficult position. Most antivaxers are not only against any and all vaccinations, but they are typically very, very pro-nutritional supplement. Since they commonly promote various supplements as being able to treat and/or cure practically anything that ails the human body, I'm sure some of them would just love to start selling massive new name brand formularies of a common vitamin D supplement. In fact - some of them already have (albeit with a MASSIVE amount of asterisks informing you their claims have not been evaluated by the FDA etc).
I'm not going to suggest taking a vitamin D supplement is a bad thing by any means, but for those who have a climate that allows, it goes without saying that the best way to get vitamin D is through natural sunlight. In colder climates taking a supplement may be necessary in the winter months etc, but when possible it is always better to take advantage of mother nature not only because it is more efficient, but because it is free... and no matter what the economy is doing, free is always a good thing.
As to Mr. Hubbs, he is convinced vaccines cause autism, so he apparently will ignore any such theory which goes against the idea, which suggests in this case he will doubt the power of vitamin D. Of course Mr. Hubbs has tried to blame autism on thimerosal in the past (a theory which has been entirely discredited) and he has attempted to blame autism on the MMR vaccine (another theory which has been entirely discredited), so if we have learned anything about Mr. Hubbs it is that he will ignore science at every turn in order to hold on to a scientifically unsupportable position.
If the growing mountains of evidence are any indication of what the future holds in terms of determining the root cause of autism, the next few years will not be kind to Mr. Hubbs and his fellow antivaxers. That being said, if someone is really concerned about their children being diagnosed with autism they would be a lot better off by giving their child a vitamin D supplement than they would by trying to skip a vaccine or two if for no other reason than we know what a lack of vaccines can result in, and nobody has ever blamed vitamin D for millions of deaths each and every year.