After Adipose tissue, the central nervous system has the highest concentration of fatty acids, making up 50-60% of the brain’s total dry weight. A type of fatty acid called polyunsaturated fatty acid, exists in high proportions in the brain’s cellular membranes. We are starting to understand there is an association between various neuropsychiatric disorders such as anxiety and depression, with people existing with these disorders showing reduced amounts of a particular type of polyunsaturated fatty acid known as omega 3.
Inflammation, in particular neuroinflammation, is one of the mechanistic factors contributing to the pathogenesis of anxiety and depression. Other neurobiological factors involving neurotransmitters, such as serotonin, are key players in regulating our mood. We are also expanding our understanding of the gut microbiome and it's now known link with the etiology of these mood disorders.
Types of Omega-3 Fatty acids
When we discuss the topic of omega 3 and mood, we are particularly looking at longer chain fatty acids such as eicosapentanoic acid and docosahexaenoic acid. We can refer to these fatty acids as EPA and DHA to make things a little easier. These fatty acids are commonly found in fatty fish, such as mackeral, sardines and salmon. Interestingly, the pink pigment in salmon is called astaxanthin and is actually a protective antioxidant of the omega 3’s found in the fish. Further to this, astaxanthin is also shown to have neuroprotective properties.
DHA and the brain
DHA can come in quite diverse forms in terms of its chemical structure. A particular form of DHA, known as lysophosphatidylcholine- conjugated DHA uses active transport between the blood brain barrier which contrasts with other forms of DHA using passive transport via a biological process called diffusion. Active transport is evidently more efficient on an inflamed brain with a known compromised blood brain barrier. Sources of this type of DHA are found in fish roe and krill oil. We can also obtain another type of fatty acid, called alpha linolenic acid from things such as nuts and seeds which can then (at lower levels) be converted to DHA and EPA.
Should I take an omega-3 supplement?
A 2023 meta-analysis on this topic showed that a supplemental dose between 1.1g-2.1 g of EPA (with a ratio at 60% EPA to DHA) is beneficial in reducing the severity of depression and anxiety related symptoms. A supplement is likely more beneficial if you cannot consume oily fish regularly (at least 2, ideally 3 serves per week). If you are considering supplemental omega 3, please remember that there are contraindications with supplements, and it would be worth while discussing the safe use of this first with your doctor or dietitian.
Christos F. Kelaiditis, E.Leigh Gibson, Simon C. Dyall, Effects of long-chain omega-3 polyunsaturated fatty acids on reducing anxiety and/or depression in adults; A systematic review and meta-analysis of randomised controlled trials, Prostaglandins, Leukotrienes and Essential Fatty Acids, Volume 192, 2023, 102572, ISSN 0952-3278, https://doi.org/10.1016/j.plefa.2023.102572, (https://www.sciencedirect.com/science/article/pii/S0952327823000418)