Fish oil may help against depression

Depression is often caused by brain inflammation, and it looks as if high-dosed supplementation with EPA, a type of omega-3 fatty acids found in fish oil, may help as it reduces depression in patients with elevated inflammation markers in the blood. This was shown in a study that is published in The Journal of Clinical Psychiatry.

The study involved 61 adults diagnosed with clinical depression. All participants were overweight and their BMI was above 25. Also, they had elevated blood levels of C-reactive protein (CRP), which is an inflammation marker.
For a period of 12 weeks, the participants were supplemented with EPA (eicosapentaenoic acid), a type of omega-3 fatty acid found in oily fish. Daily doses of one, two, or four grams of EPA were given, and one group got placebo. It turned out that supplementation with four grams of EPA significantly reduced CRP levels in overweight participants. The scientists assume that this dose may mitigate symptoms of depression. The new study is published in The Journal of Clinical Psychiatry and supports earlier research showing that increased intake of oily fish or fish oil supplementation has a positive influence on depression.
For example, Harvard University scientists conducted a study of 155 people with severe depression. For two months, they were given either EPA (1,060 mg/day) or DHA (900 mg/day), or placebo. The study showed that EPA had the greatest anti-inflammatory effect and was therefore best against depression.
A Dutch study published in Psychoneuroendocrinology showed that patients suffering from the most severe type of depression had the lowest levels of omega-3 fatty acids in their blood. And patients suffering from both depression and anxiety had even lower levels of omega-3 fatty acids than patients who only suffered from depression. According to the scientists behind this study, supplementation with omega-3 fatty acids may represent a simple and safe add-on therapy that can correct the underlying causes of depressive symptoms in a natural way.

Inflammation, depression, and brain changes

Several studies suggest that local brain inflammation can disrupt the blood-brain barrier, thereby making is easier for harmful proteins to gain access to the brain. These proteins are able to provoke and overstimulate the immune defense. The brain inflammation can also cause oxidative stress, where free radicals cause damage to neurons and other tissues. Several studies have shown that elevated blood levels of inflammation markers in the brain’s hippocampus and striatum are linked to depression and anxiety.
It has also been seen that depression is more common in patients with rheumatoid arthritis and other autoimmune diseases that are associated with chronic inflammation.
Moreover, anti-depressive medication is unable to correct the brain inflammation, which is often the underlying cause of the depression.

Omega-3 fatty acids and their role in the brain and nervous system

The brain contains rather large quantities of EPA and DHA, for example in the membranes of the neurons. Here, these omega-3 fatty acids are a part of the neuronal synapses that exchange information. Omega-3 fatty acids also contribute to an improved blood flow, which is essential for energy levels and rapid brain activity. Furthermore, omega-3 fatty acids are involved in the formation of neurotransmitters such as dopamine and serotonin that are important for our mood.
Last but not least, omega-3 fatty acids counteract chronic inflammation that is seen with depression and many other chronic disorders. In other words, omega-3 fatty acids have several functions that are important for brain health and mood.

The right balance between omega-3 and omega-6

Omega-3 fatty acids work in an intricate biochemical interplay with omega-6 fatty acids, and it is vital to maintain the right balance. Generally speaking, omega-6 cause inflammation, while omega-3 does the opposite. Getting too little dietary omega-3 therefore increases the risk of chronic inflammation. There is a tendency to get far too much omega-6 from plant oils, margarine, ready meals, junk-food, French fries, and chips and that increases the risk of inflammation. A higher intake of omega-3 and less omega-6 is therefore beneficial, not only when it comes to preventing depression and other lifestyle diseases that are associated with chronic inflammation, but for health in general.

References:

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

Chieh-Hsin Lee et al. The Role of Inflammation in Depression and Fatigue. Frontiers in Immunology 2019

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

Robert M. Carney et al: Baseline Blood Levels of Omega-3 and Depression Remission: A Secondary Analysis of Data From a Placebo-Controlled Trial of Omega-3 Supplements. The Journal of Clinical Psychiatry. 2016