Researchers have found that oral cholecalciferol in doses of 100,000 IU every two weeks significantly reduced disease activity in clinically isolated syndrome and early relapsing‑remitting multiple sclerosis. Multiple sclerosis typically starts with an acute episode involving the central nervous system, such as inflammation of the optic nerve, the spinal cord, or brainstem syndromes. This combination of initial signs is termed a clinically isolated syndrome (CIS), although CIS does not always convert to MS. In the D‑Lay MS randomized clinical trial, investigators conducted a parallel, double‑blind, placebo‑controlled study comparing high‑dose cholecalciferol versus placebo in untreated CIS. Eligibility criteria included adults aged...