Widespread deficiencies of vitamin D and omega-3 fatty acids increase the risk of depression

Depression affects more and more people and causes symptoms such as chronic low mood, fatigue, and sleep disturbances. The risk increases during the winter months, and untreated depression is one of the leading causes of suicide. Since many people experience side effects from antidepressant medication, researchers have begun to focus a lot more on the role of diet. According to a review published in Clinical Nutrition, widespread deficiencies of vitamin D and omega-3 fatty acids increase the risk of depression. In the review, the researchers explain how vitamin D and omega-3 fatty acids affect the nervous system and mood. In addition, both nutrients counteract chronic inflammation in the brain, which in itself increases the risk of depression and other neurological disorders.

Mood swings have always been a natural part of life, whereas depression is a medical condition characterized by persistent sadness. Other typical symptoms include extreme fatigue, hopelessness, low self-esteem, irritability, anxiety, sleep disturbances, altered appetite, and social withdrawal. Even bright memories from the past can be overshadowed by dark mental clouds. In severe cases of depression, talk therapy is combined with antidepressant medication such as SSRIs, and electroconvulsive therapy is used in the most severe cases. Unfortunately, many people seek treatment too late, and antidepressant medication is often associated with limited effectiveness and serious side effects.
Since depression remains one of the leading causes of suicide, much more should be done to address the complex underlying factors, including nutritional deficiencies that may negatively affect mental health. In the new review article, the authors examined the influence of vitamin D and omega-3 fatty acids on the formation of neurotransmitters and on the regulation of inflammation and hormonal imbalances – both of which are key factors for mood and overall health.
Using databases such as PubMed, Scopus, Web of Science, and PsycINFO, and search terms including depression, vitamin D, omega-3, nutritional psychiatry, and mental health, the authors identified a number of relevant controlled studies and meta-analyses. The new review found the following:

The role of vitamin D in the nervous system and mood

• Most brain cells and regions have vitamin D receptors (VDR)
• Regulates the activity of neurotransmitters
• Reduces inflammation, including neuroinflammation, which damages nerve cells
• Affects neuroplasticity - the brain’s ability to change in response to experiences, activities, and stimuli
• Improves cognitive functions and mood regulation.

The role of omega-3 fatty acids in the nervous system and mood

• The brain contains significant amounts of the omega-3 fatty acids DHA and EPA
• DHA is a structural component of nerve cell membranes, where it regulates nerve impulses, communication between nerve cells, and other metabolic activities
• EPA reduces inflammation through other mechanisms, including neuroinflammation
• DHA and EPA optimize the formation of the neurotransmitter serotonin, which affects mood, sleep, and appetite

The authors therefore conclude that supplementation with vitamin D and omega-3 fatty acids may be a promising strategy as part of the treatment of depression. Adequate vitamin D and omega-3 intake is also important for preventing depression and other neurological disorders.

How much vitamin D and omega-3 do we actually need?

Strong summer sunlight is the most important source of vitamin D, as we produce it in the skin from UVB rays and a cholesterol precursor. However, during winter at northern latitudes, the sun is too low in the sky to enable the synthesis of vitamin D, which is a major reason for the increasing prevalence of winter depression.
In addition, older people, individuals with dark skin, those who are overweight, and people with diabetes have more difficulty producing or activating the vitamin. Official daily recommendations for vitamin D are 5-20 micrograms, but there is no guarantee that these amounts will optimize blood levels, which should ideally be above 75 nmol/L throughout life. If vitamin D deficiency is identified in connection with depression, stronger daily supplements are recommended. According to the Danish Veterinary and Food Administration, referring to the EU, the upper safe limit is 100 micrograms daily for adults and children over 11 years.
Fatty fish and fish oil supplements are the best sources of the omega-3 fatty acids EPA and DHA. According to the Danish Veterinary and Food Administration, we should eat at least 300 grams of fish per week, of which 200 grams should come from fatty types such as anchovies, herring, and mackerel. Farmed fish, such as salmon, contain much less omega-3 than wild fish.
If depression is rooted in neuroinflammation, higher doses of omega-3 fatty acids are needed (1,000 -1,200 mg of EPA per day.) This amount can easily be obtained by taking a high-quality fish oil supplement and reading the label carefully. It is also important to note that it takes about a month to achieve the optimal effect, and the effect diminishes correspondingly within a month after stopping supplementation.

References:

Muhammad Liaquat Raza et al. Nutritional interventions in depression: The role of vitamin D and omega-3 fatty acids in neuropsychiatric health. Clinical Nutrition 2025

Tuomas Mikola, et al. The effect of vitamin D supplementation on depressive symptoms in adults: A systematic review and meta‐analysis of randomized controlled trials. Critical Reviews in Food Science and Nutrition, 2022.

David Mischoulon et al. Omega-3 Fatty Acids for Major Depressive Disorder with High Inflammation: A Randomized Dose-Finding Clinical Trial. The Journal of Clinical Psychiatry. 2022

Carisha S. Thesing et al. Omega-3 and omega-6 fatty acid levels in depressive and anxiety disorders. Psychoneuroendocrinology. 2018