We talk generally about saturated fats and poly or mono unsaturated fats. But there is a lot more to the fat story than this.
Let’s deal with the polyunsaturated essential fatty acids: Omega-6 and Omega-3,
What are they?
Essential fatty acids are just that: essential fats that are required in the body for normal growth and development to occur. However, they are not produced by our bodies (1). For this reason, we need to get them through our diet (or supplementation).
The two essential fatty acids are called Omega-6 (linoleic acid -LA) and Omega-3 (alpha-linolenic acid ALA) (1).
These are found in nuts and in the seeds of plants and oils made from the seeds. Good sources of Omega-6 include oils such as corn, sunflower, soybean, and safflower.
Omega-6 fats make up most of polyunsaturated fats in a typical Western diet and are required for the synthesis of hormones and for growth(2).
The story is not so straight forward for Omega-3. This is because ALA (Alpha-linolenic acid) needs to be converted into long-chain fats in our body called EPA (eicosapentaenoic acid) and (DHA) docosahexaenoic acid)(3).
These long-chain fats are required for:
- maintaining membranes
- the development of our brain and eyes
- regulation of our metabolism
- anti-inflammatory activity
- regulating our blood pressure and cholesterol(3)
These Omega-3 fats may also protect against cardiovascular diseases and alleviate the symptoms of rheumatoid arthritis based on current research in this field(3).
The best source of Omega-3 is fish, especially oily fish (see detailed note on this below). If you don’t eat fish, other sources include walnuts, flaxseed/linseed oils, chia seeds, tofu, soybeans, and canola oil(3). A variety of these sources should be consumed to increase your Omega-3 intake(3).
The Omega-3 and Omega-6 relationships
It was thought in the past that too much Omega-6 fatty acid may decrease the conversion of ALA into DHA and EPA in the body. However, the rule of thumb presently is to increase the amount of long chain Omega-3 in the diet rather than restrict the Omega-6(2).
Fish as a source of Omega-3
The best source of Omega-3 in our diets is fish, particularly oily fish. Due to this, it’s recommended we eat 2 servings (150g) of fish per week, with one of these serves being an oily fish(4). Rich sources of Omega-3 include mackerel, tuna, salmon, crab, whitebait, swordfish, sardines, herring, and trout. White fish also contain Omega-3, so eating varieties of this such as gurnard and hoki is recommended also.
Safety of consuming fish
Fish and shellfish are a great source of protein, low in saturated fat and are the best source of Omega-3 in our diets. However, the muscle and tissue of fish and shellfish can contain differing levels of the toxin methylmercury(5). Mercury can negatively affect the nervous system with the developing nervous system of unborn babies being particularly sensitive to mercury toxicity(5). Fish that live longer or are predatory fish have much higher levels of mercury than others. These fish should be limited in your diet, especially during pregnancy and for young children (below 6 years old)(5).
The fish that contain higher levels of mercury in New Zealand and should be eaten only once per week by the general population include(5):
- shark (flake)
- Orange Roughy
For more information about mercury in fish and recommendations for children and pregnant women, go to the New Zealand Food Standards website.
Omega-3 supplement advice: It can be hard to consume adequate amounts of Omega-3 through the diet if you don’t eat fish. Taking a supplement may be desirable but expert advice should be sought on this front.
1. Dietitians Association of Australia. Omega-3 Fatty Acids and Vegetarian Diets. 2014 –[cited 12 July 2017]. Available from: http://www.pennutrition.com.ezproxy.auckland.ac.nz/docviewer.aspx?id=11713
2. Rose Carr. Science update: Omega-3 and Omega-6 fats. Healthy Food Guide. 2017 –[cited 14 July 2017]. Available from: https://www.healthyfood.co.nz/articles/2011/june/science-update-omega-3-and-omega-6-fats
3. British Dietetic Association. Food Fact Sheet- Omega-3. 2014 –[cited 12 July 2017]. Available from: https://www.bda.uk.com/foodfacts/omega3.pdf
4. Ministry of Health. Eating and Activity Guidelines for New Zealand Adults.
5. Food Standards Australia and New Zealand. Mercury in Fish. 2011 –[cited 14 July 2017]. Available from: http://www.foodstandards.govt.nz/consumer/chemicals/mercury/Pages/default.aspx