The review also observed a direct relationship between the polyunsaturated fatty acids (PUFAs) dosage and the effect size on depression, with eicosapentaenoic acid (EPA) demonstrating a greater effect over docosahexaenoic acid (DHA).
Regarding the ‘British Journal of Nutrition’ published findings, the Chinese researchers conclude: “Omega-3 PUFAs supplementation could be considered as an effective therapeutic adjuvant approach in relieving depression symptoms.”
Omegas and the mind
Depression is a highly common condition of the modern world, affecting an array of areas such as sleep quality, energy levels, and appetite. The World Health Organization has previously predicted that it may affect 280 million people globally, with levels ever-increasing following the Covid-19 pandemic.
Research has shown that factors such as nutrition, genetics, environment, and hormones play major roles in the pathogenesis of depression, with alterations noted in the levels of serotonin, dopamine, and gamma -aminobutyric acid (GABA).
Following long-term concerns around the effectiveness and adversities associated with the use of anti-depressants, there has been significant interest in investigating further causes of depression and more natural treatment methods. It is known that long-chain fatty acids (n-3 PUFAs), specifically EPA and DHA, have significant benefits such as anti-inflammatory and subsequent neuro-inflammatory inhibitory activities.
Whilst previous meta-analyses have investigated the association between omega-3 FAs and depression, there has been a lack of a reached conclusive outcomes. Thus, the researchers conducted an umbrella review of such meta-analyses to further establish a definite conclusion.
The researchers searched the databases of PubMed, Scopus, Embase, Web of Science, and Cochrane Central Library to collate meta-analyses investigating the effects of n-3 PUFAs on depressive symptoms. Twenty-two meta-analyses were included following the search.
The findings revealed a significant improvement effect on depressive symptoms in the majority of included studies, with 16 effect sizes displaying this association.
Supplement dosages displaying significant effects ranged from 0.09-3.4g of DHA and 0.009-6.2 g of EPA.
The association was observed to be more pronounced in those with major depressive disorder (MDD), when compared to those with mild or normal depressive symptoms. Furthermore, there was a direct relationship between the dosages of omega-3 PUFAs and the effect size on depression, with EPA demonstrating a greater effect over DHA.
Based on the findings, the report concluded that omega-3 supplements may present an efficacious add-on therapeutic approach in relieving depression symptoms.
Explaining the mechanism of action, the researchers said: “Omega-3 PUFAs have been proven to influence the activity and structure of brain through affecting adult neurogenesis and synaptogenesis by increasing the signalling factors involved in neurogenesis, such as brain-derived neurotrophic factor (BDNF), cAMP response element-binding protein (CREB), or calcium/calmodulin-dependent protein kinase II (CaMKII).
“In one pathway, omega-3 PUFAs might increase the expression of dopamine receptor; whereby increase dopamine activity as a neurotransmiter in restoring the mood (81). As well, omega-3 PUFAs were effective in balancing the low level of BDNF (brain-derived neurotrophic factor) among depressed patients. BDNF could boost the action of antidepressant agents,” they added.
Yet, the report emphasised the need for further research to account for significant between-study heterogeneity and a lack of insight into factors such as dose, duration of supplementation and gender.
Source: British Journal of Nutrition
“Clinical impacts of omega-3 fatty acids supplementation on depression symptoms: An umbrella review of meta-analyses”
Yi Lu, Dongdong Qiao and Guolin Mi