Vitamin d and fish oil fail to prevent depression in massive trial
NCT ID NCT01696435
First seen Jun 27, 2026 · Last updated Jun 27, 2026
Summary
This study tested whether taking daily vitamin D or fish oil supplements could prevent depression in over 18,000 adults without significant mood issues at the start. Participants were followed for about 5 years. The results showed that neither supplement reduced the risk of developing depression or improved mood scores compared to a placebo.
What this could mean
Our plain-language read of the trial. This is informational only — not medical advice or a prediction.
Active substance
vitamin D3 (2000 IU daily) and omega-3 fatty acids (fish oil, 1 gram daily)
What this could lead to
If effective, these common supplements could offer a simple, low-cost way to help prevent depression in the general population.
What could go wrong
This large, completed trial found no significant reduction in depression risk or improvement in mood scores with either supplement compared to placebo.
Disclaimer
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This is a summary of
the original study
.
Summaries may miss details or leave out important information. Before applying or accepting participation, make sure you have read and understood the full study. Curemydisease.com takes no responsibility whatsoever for anything missed, misunderstood, or acted upon as a result of our summary — we know it does not capture everything.
This is a summary of the original study . Summaries may miss details or leave out important information. Before applying or accepting participation, make sure you have read and understood the full study. Curemydisease.com takes no responsibility whatsoever for anything missed, misunderstood, or acted upon as a result of our summary — we know it does not capture everything.
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Conditions
The condition(s) this trial relates to.
As listed by the trial registrant
The condition terms exactly as the trial's registrant entered them.
Contacts and locations
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Locations
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Brigham and Women's Hospital
Boston, Massachusetts, 02215, United States