There are a number of epidemiological studies that suggest a clear relationship between levels of vitamin D in the body and mental well being, but to date there has not been a large scale randomised controlled trial that proves that vitamin D supplementation (serum 25-hydroxyvitamin D levels) can improve mental health.

An Australian research team have conducted a double-blind, placebo controlled trial of older women (aged 70 or over) to assess the impact of a single large oral dose of vitamin D3 (cholecalciferol) once a year on their mental well-being.

Participants were randomly assigned to receive treatment every autumn/winter for 3-5 consecutive years:

• 500,000 IU vitamin D(3) (cholecalciferol), or
• Placebo

Health outcomes were measured using a number of well respected tools, but they did not use an instrument that focused specifically on depression in older people:

• General Health Questionnaire
• 12-item Short Form Health Survey
• Patient Global Impression-Improvement scale
• WHO Well-Being Index

Serum 25-hydroxyvitamin D levels were measured in a subset of 102 participants.

The results found:

• No significant differences between the vitamin D and placebo groups when measuring mental health outcomes
• Serum 25-hydroxyvitamin D levels in the vitamin D group were 41% higher than the placebo group 12 months following their annual dose. Despite this difference, scores from the questionnaires did not differ
• Furthermore, there was no interaction between those on antidepressant/anxiety medication at baseline and the treatment groups.

The researchers concluded:

The lack of improvement in indices of mental well-being in the vitamin D group does not support the hypothesis that an annual high dose of vitamin D(3) is a practical intervention to prevent depressive symptoms in older community-dwelling women.

So what does this tell us about vitamin D and mental health? Is an annual dose of vitamin D the best way to optimise levels in the body, or would more regular supplementation work better? We await publication of high quality trials in this field with interest.

Sanders KM, Stuart AL, Williamson EJ, Jacka FN, Dodd S, Nicholson G, Berk M. Annual high-dose vitamin D3 and mental well-being: randomised controlled trial. Br J Psychiatry. 2011 May;198(5):357-64. [PubMed abstract]