Fats are categorised into saturated, monounsaturated and polyunsaturated fatty acids. Fats are essential for our health as it acts as the aids the absorption and act as a carrier for fat-soluble vitamins and provides us with energy. It is recommended to eat them in small amounts and to choose unsaturated oils and spreads when possible1,2**. The polyunsaturated fats include omega-3, omega-6 and omega-9. They are essential fatty acids, meaning we must include a small quantity of them as part of a balanced diet3.
**There is one exception which is trans fatty acids. These structurally are unsaturated fatty acids but behave like saturated fats and it is recommended to limit them in our diets1.
About omega-3 and dietary sources.
Omega-3 is a fatty acid which comes in three different forms: eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) ad alpha-linolenic acid (ALA)4.
We cannot make ALA in our bodies so we must consume it through the diet. ALA comes from plant sources such as flaxseeds, walnuts, and leafy green vegetables. We can however make EPA and DHA from ALA in our bodies however it is more efficient to eat foods rich in them. Oily fish is a particularly good source of EPA and DHA, other sources include other seafood, microalgae (not blue-green algae), grass-fed animals and eggs. EPA and DHA give rise to the production of anti-inflammatory eicosanoids4,5.
The potential health effects of omega-3.
Research shows that omega-3 fatty acids have potential health benefits including reducing the risk of cardiovascular disease, cancer and other chronic disease which may be through the anti-inflammatory effect of the eicosanoids they give rise too5,6. The association is much stronger in EPA and DHA, which has been attributed to the inefficient conversion of ALA to EPA and DHA6.
The European Food Safety Authority has approved several health claims for EPA and DHA which include, “DHA and EPA contribute to the normal function of the heart (0.25g/ day)” and “DHA contributes to maintenance of normal brain function (0.25 g per day)”7. The full list can be found here. Overall, it is recommended to eat 2 portions of fish a week, one of which is oily, and if you don’t eat fish you can consume it through omega-3 rich plant foods8,9.
Considerations with eating fish.
For several reasons one may reduce the amount of fish part of their diet.
• Regarding sustainability, you can look for labels such as the Marine Stewardship Council (MSC) on products. The MSC label is only applied to wild fish and seafood which have been sustainably fished10.
• If you do not eat fish at all, seaweed and microalgae contain some EPA and DHA and some eggs and dairy products are enriched with omega-34,9.
• There are currently no recommendations in the UK for supplementing omega-3. The British Dietetics Association recommend if considering a supplement to check the label to ensure there is approximately 450mg of EPA and DHA in the supplement, this would provide you with the same amount from one to two portions of fish per week11.
• If you follow a vegetarian diet or do not consume risk, recommendation for maximising ALA conversion to EPA and DHA include regular consumption of good dietary sources of ALA, limiting omega-6 fats, limiting alcohol and caffeine intake and consuming a balanced diet4.
About omega-6 and dietary sources.
The most common type of omega-6 is linoleic acid (LA). In our bodies LA is converted to arachidonic acid (AA) which produces pro-inflammatory eicosanoids. LA is found in vegetables oils including sunflower and safflower oil and some nuts3,4.
The potential health effects of omega-6.
AA plays an important role in the functioning of all our cells, especially within the central nervous system, skeletal muscle and immune system12,13. However, when consumed in too higher quantities these pro-inflammatory eicosanoids can lead to chronic inflammation which can increase the risk of metabolic syndrome, heart disease and several other chronic illnesses. This is because the ratio of omega-6 omega-3 compete for the same enzymes, is you have too much omega-6 which promotes inflammation, you reduce the amount of omega-3 which reduces inflammation. It is recommended to have a ratio of between 1: 1 - 2:1 of omega-6: omega-3 fatty acids. Consumption of a typical Western diet often provides much more omega-6 than required1,12,13.
Overall, we need some omega-6, but we do not need too much. Therefore, it may be worth swapping oils with a high omega-6 content such as sunflower oil with ones with a lower omega-6 content such as olive oil or flaxseed oil.
About omega-9 and dietary sources.
A final consideration is given here to omega-9. Oleic acid is a monounsaturated fatty acid and is the most common type of omega-9. The main type of fatty acid found in olive oil is omega-914.
The potential health effects of omega-9.
Oleic acid has been shown to significantly reduce inflammation in mice with sepsis14. Further, consumption of olive oil has been associated with having a wide range of physiological benefits including on autoimmune and inflammatory diseases and some cancers15. Overall, it is suggested to include small amounts of unsaturated fats rich in omega-9 as part of a balanced diet.
1. Create recipes inspired by a dietary pattern rich in unsaturated fats such as the Mediterranean diet.
2. Aim to have 2 portions of fish a week, one of which is oily.
3. Swap oils rich in omega-6 for those which contain less such as flaxseed oil and olive oil.
• British Nutrition Foundation. Fats1.
• Heart UK. Omega 3 fats16.
• Marine conservation society. Good Fish Guide – Your Guide to Sustainable Seafood17.
This blog post was written by Emilia Fish, a Food Science and Nutrition graduate MSc Clinical and Public Health Nutrition student at UCL. She has interned as part of the Nutrition Rocks team, has experience in Food Science labs and enjoys sharing simple, evidence-based nutrition on @nutritionnourishment. Emilia has recently launched a second series of her podcast, The Nutrition Nourishment Podcast: Sharing Our Journeys.
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