Study was in an elderly cohort with cognitive impairment. This is a cohort more likely to have nutrition and diet problems and spend all of their time indoors. I haven’t found the full study but the results look marginal for a narrow group.
Then there’s this important note in the highlights:
Higher daily Vitamin D intake may impact cognition in persons with sleep disturbance and MCI.
More is not better with Vitamin D. Correcting deficiencies is good but the mega dosing trend is not.
Top comment it pertinent.