Depression and Fish Oil Supplementation 

Evidence suggests caution is required, says Consultant Dietician Dr Lynn Harbottle. 

Last year, 25 year old Megan came to see me with digestive problems. During our consultation, she mentioned she also suffered from depression. A few months later, during a follow-up, she described how she had improved her diet. She was eating more regularly, drinking more water and had reduced her intake of sugary food, refined wheat products, hydrogenated fats, caffeine and alcohol. In addition, she had started taking a multivitamin and mineral, fishoil capsules and a supplement to facilitate digestion.

Megan said “I didn’t do everything at once, but in stages. Although my digestive issues cleared up, I still felt depressed. Then I started taking the fishoils and my depression lifted unusually quickly. I also noticed my mood after the depression was better than after previous episodes. I believe that this was in part due to the fishoils.”

Megan’s experience is by no means unusual in clinical practice. It is widely known that mental well-being is affected by what we consume and that our brain can only function efficiently if we provide it with the nutrients it requires. Those eating diets lacking in essential fatty acids EPA and DHA, amino acids, vitamins and minerals, or those who have a higher requirement for such nutrients, are at higher risk of developing depressive conditions.

Consultant Dietitian, Dr Lynn Harbottle, has recently reviewed the evidence linking aspects of our diet to depression on behalf of the British Dietetic Association. She explains that the evidence indicates a link between low intakes of fish and high levels of depression and suicide across countries. “Studies of those with depression suggest they have lower levels of omega 3 fatty acids in their blood. Some studies also suggest that improvements in depressive symptoms may be possible when pure EPA is given together with an antidepressant. Interestingly, in these studies a 1 gram dose was shown to give the best result – giving more was not found to be helpful.”

However, Dr Harbottle warns that fishoils should not be seen as a miracle cure for depression or any other condition for which it is marketed. Studies in genetics show that although fishoils have an anti-inflammatory effect for some, for others the effect is to increase the inflammatory effect, and getting the wrong dose can upset the body’s equilibrium. Cod liver oil is high in vitamin A, which is toxic in high doses and can increase the risk of osteoporosis by affecting calcium balance. Many commercial fishoils are also contaminated with marine pollutants. For these reasons caution is advised. Dr Harbottle says “This is a highly complex subject and further research is needed into the optimal ratio of essential fatty acids, micronutrient intake and other factors that might improve mental health.”