A wide range of functionality in the human body is exhibited by eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are ω-3 fatty acids that are abundant in fish oil, and their metabolites such as eicosanoids and docosanoids. In particular, DHA is known for its deep involvement in brain function, while EPA and its metabolites are deeply involved in circulatory and immune functions. However, because neurons in the human brain are deficient in delta-6-desaturase, DHA is not synthesized in the brain and we must acquire DHA from our diet. Additionally, since it has been reported that the amount of DHA in the brain is lower in the elderly and patients with neuropsychiatric disorders such as Alzheimer's disease, it is speculated that decreased DHA intake is associated with the onset and progression of neuropsychiatric disorders. Recently, it has been reported that there are lower serum EPA and DHA levels in mothers with postpartum depression and those suffering from depression. Despite the necessity of eating fish as shown in such research, total fish consumption in Japan continues to decline every year. This decline is due to reasons such as the westernization of the Japanese diet to a meat-based diet, an increased aversion to fishy odors due to the improvement of the sensory cleanliness of modern people, and the complexity of eating fish in terms of removing bones, etc. Consequently, there are concerns regarding the effects on health of modern people due to the decrease in DHA and EPA intake, especially on the brain function of pregnant women, infants, and the elderly. So, are there any alternatives to fish oil?
Alpha-linolenic acid (ALA), which is abundant in perilla oil and linseed oil, is an essential fatty acid and is the same omega-3 fatty acid as DHA and EPA. Since ALA obtained through diet is converted to EPA and DHA in vivo, it is expected to have a wide range of functionality via EPA and DHA. However, unlike rodents, the conversion rate from ALA to EPA is extremely low at 0.1%to 21%. The same is also trued for DHA, at 0.1% to 9%. In order to establish the functionality of ALA and its intake effect in humans, it is necessary to accumulated further research results targeting humans.
Recently, the researchers conducted a human intervention study in adults and the elderly to clarify the functionality of perilla oil, which is composed of approximately 60% ALA. The following findings were obtained, thus suggesting the possibility of using perilla oil to improve brain function.
- 1. It was suggested that 12 months of perilla oil intake by workers with an average age of 48 years increased ALA and EPA in the erythrocyte membrane, while also decreasing depression and increasing motivation. (Hashimoto M. et al., Foods (2020), 9: 530-44.)
- 2. It was suggested that 12 months of perilla oil intake in healthy home-based elderly individuals with an average age of 71 years increases ALA in the erythrocyte membrane and antioxidant activity (biological) in the body, improves frontal lobe function, and heightens motivation. (Hashimoto M. et al., Foods (2021), 10: 1130-45.)
- 3. It was suggested that 12 months usage of soft capsules containing perilla oil and ponkan peel powder containing nobiletin increases red blood cell membrane ALA and EPA/DHA, as well as neurotrophic factor (BDNF) and in vivo antioxidant activity, while also improving cognitive function. (Currently being submitted for publishing.)
Few results of human intervention studies with ALA have been reported. Our results suggest that ALA intake increases antioxidant activity in the body, enhances the mental state (for example, decreasing depression and heightening motivation), and suppresses cognitive decline in the elderly. It has also been reported that the conversion rate from ALA to DHA is increased by estrogen and flavonoids. Although it is necessary to collect more data in the future, for people who dislike eating fish, it is possible to expect maintained and improved brain function through the more efficient intake of omega-3 fatty acids by heightening the conversion from ALA to DHA while considering dietary content.
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