What is omega-3?
Omega-3 is a polyunsaturated fatty acid (PUFA) which is important for good health. The PUFA has three different forms:
- Eicosapentaenoic acid (EPA)
- Docosahexaenoic acid (DHA)
- Alpha-linolenic acid (ALA)
ALA is considered an essential fatty acid, as our bodies cannot create it by itself. We therefore need to obtain the nutrient from our diet.
EPA and DHA can technically be produced in the body by converting ALA when consumed. However this conversion isn’t very efficient and should not be relied on as intake of the nutrient.
What are the links between omega-3 and brain health?
Research shows that a diet rich in omega-3, and PUFAs in general, is linked to a decreased risk of heart disease and intake is also important for brain health.
Omega-3 fatty acids play vital roles in the synthesis of cellular membranes for example ensuring brain cells can communicate effectively, promoting the production of new brain cells, reducing inflammation and enhancing activity of the dopamine (reward) and serotonin (happy) hormone systems.
Perhaps this makes sense as the brain is the most lipid rich organ in the body coming it at 60% lipid (fat; dry weight). This is mainly from the phospholipid composition of cellular membranes.
A 2016 meta-analysis of 26 studies found a 17% lower risk of depression with higher fish intake, in both men and women (1). Another meta-analysis of over 1000 people, conducted in 2019, found that supplementing with omega-3 PUFAs, with 60% or more EPA, had a therapeutic effect on the improvement of depressive symptoms (2).
While omega-3 PUFA levels have been linked to inflammation and depression, evidence of this is mixed from randomised controlled trails which most evidence coming from observational studies. However, Kiecolt–Glaser et al 2011 did find a reduction in anxiety symptoms in student participants that were supplemented with omega-3 compared to a placebo group. The reduction in anxiety symptoms associated with omega-3 supplementation provided great initial evidence that omega-3 may have potential anxiolytic benefits for individuals without an anxiety disorder diagnosis.
The Mediterranean Diet (MD) is a traditional diet rich in polyphenols from fruit and vegetables, fibre, nuts and seeds which has been found to have beneficial effects on mental health (4). It’s thought that the diversity of the MD is the key to its success in supporting mental health. Although there is no single nutrient in isolation that can provide a miracle cure to mental health, omega-3 fatty acids are a significant component of the MD through intake of oily fish, which has been linked to improved mental health outcomes through following a MD. Including reducing psychotic symptom severity and improving positive and negative symptoms of schizophrenia (5).
How much do we need?
Quantities of omega-3 fatty acids required in the body are not as straightforward as they are for vitamins and minerals. Government guidelines recommend that we get a total of 6.5% of our daily calories from PUFAs. Within this 0.2% of daily calories should come from omega-3.
Practical recommendations indicate we should be consuming 2 portions of fish per week, one of which should be oily fish. One portion of cooked fish is roughly 140g.
Eating too much oily fish can have some health risks. This is due to small amounts of pollutants which can build in the body. To avoid this, it is recommended to not exceed 4 portions per week. For women of childbearing age, pregnant or breastfeeding, this should be limited to 2 with a minimum of 1 per week.
Where can we find Omega-3?
Oily fish is quite well known as the major source of omega-3. This is correct, oily fish such as salmon, mackerel, herring, kipper and sardines are a great source of EPA and DHA. EPA and DHA can also be found in shellfish, seaweed (not recommended more than once per week) and fortified products such as eggs and dairy products.
Plant sources of DHA and EPA are limited, individuals following a strict vegan diet should consider a supplement of DHA and EPA from algae oil (450mcg), especially if not consuming large quantities of food containing ALA. Although it is best to try to get omega-3 from foods, Omega-3 supplements may be beneficial for other individuals that have low intake of fish. Always consult your GP, a registered dietitian or nutritionist before taking any new supplements.
ALA is quite abundant in foods such as chia seeds, linseeds, hemp seeds, nuts such as pecans, hazelnuts and walnuts, and oils such as soybean, flaxseed and walnut, soyabeans (and products made from soyabeans such as tofu) and green leafy vegetables.
Omega-3 is an important nutrient for good health, particularly cognitive health relating to the brain. Emerging evidence suggests supplementing with omega-3 can improve mental health outcomes including reduced depressive symptoms. Sticking to recommendations of two portions of fish per week, one of which oily fish is recommended.
- Li et al (2016) https://pubmed.ncbi.nlm.nih.gov/26359502/
- Liao et al (2019) https://www.nature.com/articles/s41398-019-0515-5
- Kiecolt-Glaser et al (2011) https://www.sciencedirect.com/science/article/pii/S0889159111004685?casa_token=10vJvRfKjaoAAAAA:InC0u1ZZhkuyAmHkRBacvn1segf8QEJw_uUXxoTWBBP3TP8wFC0hx1jP2x-LzaGpzpEgAythDkM
- Jacka et al (2017) https://bmcmedicine.biomedcentral.com/articles/10.1186/s12916-017-0791-y?mod=article_inline
- Hsu et al (2020) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7333328/#Abs1title
- NIH omega-3 Fatty Acids fact Sheet https://ods.od.nih.gov/factsheets/Omega3FattyAcids-HealthProfessional/