Supplementation with 14,000 IU/d resulted in a 32% reduction in new brain lesions detected by MRI compared to placebo.

This is a much higher dose than the Institute of Medicine recommends as the daily upper tolerable intake (10,000 IU per day). People with multiple sclerosis have been shown to have SNPs that affect vitamin D metabolism. It is possible that this was the reason such a high dose was used in the study.