The dose of vitamin D3 used in this study was 300 IU vitamin D3/kg body weight/day, not to exceed 5,000 IU/day. I published a paper on how vitamin D regulates serotonin and how this may be relevant for autism since serotonin acts as a brain morphogen during early brain development shaping the structure and wiring of the brain. You can read more about the mechanism that I propose in my publication here: https://www.ncbi.nlm.nih.gov/pubmed/24558199