Abstract
Omega-3 polyunsaturated fatty acids is a generic term that encompasses eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are abundant in fish, and α-linolenic acid, which is abundant in perilla oil. These fatty acids became well known following an epidemiological study conducted in Greenland about 50 years ago. EPA formulations, with their putative prophylactic effect against cardiovascular disease, first became clinically available in the 1990s in Japan. There were reports of their association with mental health, especially depression, and from around the year 2000 several epidemiological studies and clinical trials were conducted. This article introduces the epidemiological studies and clinical trials conducted in Japan and the knowledge gained.
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Key Points
This review provides an overview of epidemiological studies and clinical trials conducted in Japan on mental health and omega 3 fats. The research suggested that serotonin and dopamine in the brain are involved in the mechanism of action of omega-3 PUFAs. In an animal study, a diet deficient in omega-3 PUFAs increased 5-HT2 receptor density but decreased dopamine D2 receptor density. In a human study, a positive correlation was found between plasma DHA level and serotonin metabolites in cerebrospinal fluid in healthy individuals. The findings indicate that omega-3 PUFAs likely affect serotonin metabolism, thereby ameliorating depressive symptoms. Other likely mechanisms include the regulation of corticotropin-releasing hormone, inhibition of protein kinase C, modulation of heart rate variability, enhancement of dendritic branching and synapse formation, suppression of neuronal apoptosis, and improvement of cerebral blood flow. Dietary Reference Intakes for Japanese provide the recommended total consumption of omega-3 fatty acids（α-linolenic acid, EPA, DHA, and other omega 3 PUFAs) by age and sex. These are 2.1 g or 1.6 g daily consumption for men and women aged 30-49 years, respectively, and 2.4 g or 2.0 g daily consumption for men and women aged 50-69 years. Omega-3 PUFA consumption is associated with amelioration of depressive symptoms. If nutritional intervention can ameliorate depression even slightly, it will be of great significance in health economics.