Five years of vitamin D moved a depression score by 0.01 points
In 18,353 adults over 50, five years of 2,000 international units of vitamin D3 a day moved the depression questionnaire 0.01 points, against the half-point set in advance.
What the study found
The mood trials rule out a benefit rather than just miss one
In 18,353 adults over 50, five years of 2,000 international units of vitamin D3 a day moved the PHQ-8 depression questionnaire score by 0.01 points, against the half-point the researchers had set in advance as the smallest change worth noticing. Its interval spans 0.04 either side of zero.
The caveat · Almost nobody started out depressed
Almost nobody in the trial was depressed at the start, so this tests whether vitamin D3 stops depression arriving, not whether it treats depression already present. Participants were not selected for low vitamin D either. Several of the authors declare payments from supplement companies, which the paper states.
What we don't know
Large trials found no mood benefit; the pooled benefit rests on small, short trials, some counted twice. What observational studies still cannot separate is whether low vitamin D brings on depression or depression keeps people indoors.