EPA and DHA deficiency? At risk for 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 that boasts a diet rich in fish, therefore, residents may show insufficient levels of omega-3 to prevent mood disorders and need to increase consumption of EPA and DHA.

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

Depression, nutrition also plays an important role

Depression is a widespread mood disorder especially in Western countries; according to the World Mental Health Survey about 5 percent of people report having had at least one episode of depression during their lifetime. According to predictions, by 2030 the disease may become one of the top three causes of years of life lost due to disability or premature death (DALY index). Therefore, the management and prevention of depression is becoming increasingly important, especially for middle-aged and elderly people. In this regard, depressive symptoms correlate with age-related cognitive impairment, as well as with signs of cognitive decline in patients with early dementia, showing how they may be a potential risk factor for dementia. At the origin of depression are most likely a combination of several factors: genetic, environmental, and psychological and biological. Another study had shown that higher fish consumption reduces the likelihood of getting depression. Nutrition can also influence the onset of depression. In particular, studies have found that individuals who consume high amounts of fish show a lower likelihood of falling into depression than those who consume it in small doses. Similarly, it has been shown that those who experience depressive symptoms have poor blood levels of omega-3s. This link may be bent by the fact that EPA and DHA, the two main omega-3s derived from fish, are essential for maintaining membrane function in neurons, where they act by regulating their fluidity and influencing neurotransmitter release. Omega-3s can act against depression and its symptoms through several different mechanisms of action: anti-inflammatory, antioxidant, and neuroprotective.

Blood omega-3 level is associated with the risk of depression

Compared with previous studies usually conducted in populations that do not consume a lot of 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, the researchers involved 1,050 men and 1,073 women over the age of 40 who were residents of Japan and underwent specific tests. The results showed that subjects with the highest concentration of EPA and DHA in their blood ran a lower risk of experiencing symptoms of depression, compared with those showing the lowest 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 percent of Japanese with the lowest omega-3 concentrations manifested 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 far lower than that of the Japanese. In the latter, the average concentrations of EPA and DHA in the blood are about 75 mg/ml and 170 mg/ml, respectively, while in the U.S., individuals 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 percent lower for EPA, and 3 times lower for DHA, than the Japanese. The relationship between omega-3 concentrations and depressive symptoms was thus found to be for levels of EPA and DHA rarely achieved by Americans or other populations on fish-poor diets.

Results to be confirmed by other 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. According to the same researchers, however, it is not possible to prove a causal relationship between omega-3 levels and depression; in fact, it cannot be ruled out that it is the depressive disorder itself that results in lower omega-3 intake due to decreased appetite. Further studies will therefore be needed 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