EPA and DHA Deficiency? Risk of Depression

A new study reveals that in the Japanese population those with the lowest concentrations of EPA and DHA in their blood are more prone to depression. Even in a nation with a diet rich in fish, residents can show levels of omega-3 insufficient to prevent mood disorders and need to increase their intake of EPA and DHA.

This was discovered by researchers at the National Center for Geriatrics and Gerontology in Aichi (Japan), published in the journal British Journal of Nutrition.

Depression: Diet Also Plays an Important Role

Depression is a very common mood disorder, especially in Western countries; according to the global Mental Health Survey, about 5% of people report having had at least one episode of depression during their lifetime. It is predicted that by 2030 the disease could become one of the top three causes of years of life lost due to disability or premature death (DALY index). Therefore, managing and preventing depression is becoming increasingly important, especially for middle-aged and elderly people. Depressive symptoms are related to age-related cognitive decline, as well as cognitive decline signs in patients with early dementia, showing they may be a potential risk factor for dementia. The origin of depression is very likely a combination of different factors: genetic, environmental, psychological, and biological. Another study showed that higher fish consumption reduces the risk of developing depression. Diet can also influence the onset of depression. In particular, some studies have found that subjects who consume large amounts of fish have a lower likelihood of becoming depressed compared to those who consume small amounts. Similarly, it has been shown that people with depressive symptoms have low omega-3 blood levels. This link may be explained by the fact that EPA and DHA, the two main omega-3s derived from fish, are essential for maintaining neuron membrane functions, where they regulate fluidity and influence neurotransmitter release. Omega-3s may act against depression and its symptoms through several mechanisms of action: anti-inflammatory, antioxidant, and neuroprotective.

Blood Omega-3 Levels Are Associated with Depression Risk

Compared to previous studies, usually conducted in populations that do not consume much fish, the new research investigated the influence of omega-3s on the pathophysiology of depression in an area characterized by high seafood consumption. During the study, researchers involved 1,050 men and 1,073 women aged over 40 years, living in Japan, who underwent specific analyses. Results showed that subjects with the highest blood concentrations of EPA and DHA had a lower risk of showing depressive symptoms compared to those with lower omega-3 levels. 

The association with depression was not found for other fatty acids analyzed, demonstrating the exclusive role of EPA and DHA in this link. Clinically, 12.5% of Japanese with the lowest omega-3 concentrations showed depressive symptoms, a value in line with data observed in other populations of similar age, such as Americans. However, the omega-3 status of Americans is much lower than that of Japanese. In the latter, average EPA and DHA concentrations in the blood are approximately 75 mg/ml and 170 mg/ml respectively, while in the United States, subjects over 60 years of age show average EPA and DHA concentrations of 14.9 mg/ml and 46.5 mg/ml respectively; that is, about 50% lower for EPA and three times lower for DHA compared to the Japanese. The relationship between omega-3 concentrations and depressive symptoms was therefore identified at EPA and DHA levels rarely reached by Americans or other populations following fish-poor diets.

Results That Need Confirmation by Further Research

According to the researchers who conducted the study, these results suggest that EPA and DHA levels may be insufficient to prevent behavioral disorders, even in populations that on average consume a lot of fish. However, the researchers state that it is not possible to demonstrate a causal relationship between omega-3 levels and depression; it cannot be excluded that the depressive disorder itself leads to lower omega-3 intake due to reduced appetite. Further studies will therefore be necessary to evaluate this relationship.

 Source: Horikawa C, Otsuka R, Kato Y, Nishita Y, Tange C, Kakutani S, Rogi T, Kawashima H, Shibata H, Ando F, Shimokata H. Cross-sectional association between serum concentrations of n-3 long-chain PUFA and depressive symptoms: results in Japanese community elders. 2015 Br J Nutr