Albert Einstein once said that “Everything should be kept as simple as possible, but no simpler.” Said in another way, and to quote Sir Isaac Newton, “We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearances. Therefore, to the same natural effects we must, so far as possible, assign the same causes.” That means that the theory that can explain the most facts is the best theory, the most parsimonious theory.
So must it be for the repeated finding of elevated mercury levels in the hair of children with autism. The most recent study, by the incredibly prolific Dr. David Geier and colleagues, found not only elevated hair mercury levels in 18 young autistic children, but that those levels correlated with the severity of autism, to the tune of a relatively high correlation coefficient (R=.58).
However, the authors must not have read Einstein or Newton, as they did not include all the possibilities in their explanation of possibilities, nor did they try to parsimoniously explain their findings. Instead, they stuck to the herd dogma, which is that autistic children must have excessive mercury exposure compared to other children. However, another possibility, one they did not discuss, was that autistic children are exposed to the same amount of mercury as other children, but autistic children have impaired ability to catabolize, or remove, mercury from their body.
Mercury is eliminated in the body by glutathione, an antioxidant that binds it and then transports it to the kidney for elimination.
Schläwicke Engström K, Strömberg U, Lundh T, Johansson I, Vessby B, Hallmans G, Skerfving S, Broberg K. Genetic variation in glutathione-related genes and body burden of methylmercury. Environ Health Perspect. 2008 Jun;116(6):734-9
And what steroid hormone upregulates or increases glutathione? Vitamin D does.
So the possibility Dr. Geier and colleagues overlooked is that autistic children have impaired abilities to remove mercury from their bodies, thus explaining their elevated hair mercury levels, an explanation that is parsimonious with the vitamin D theory of autism.
Dr. Geier was pleased with an R value of .58, but that is nothing compared to the recently discovered R value in the relationship of vitamin D levels to autism rating scale severity (R=-.84) or the R value of anti-neural antibodies to 25(OH)D levels (R=.-86).
The sages said to keep it simple and assign the same cause to a variety of different facts. If you know of a fact that the vitamin D theory of autism cannot explain, let me know. The vitamin D theory remains parsimonious, and thus the vitamin D theory of autism is alive and well, at least according to the writings of Einstein and Newton.