Of the various forms of omega fatty acids, it is the families of polyunsaturated fats known as omega-6 and omega-3 that are most essential for health. These types of fat contain numerous sub-types, each of which has different actions and numerous by-products. Maintaining balance between these families is vital for long-term health and excess levels of one family over another is detrimental.
It is well documented that most people following a typically Western diet are deficient in these essential fats and in particular the omega-3 family. Implications of omega-3 deficiency for health are profound and increase susceptibility to health issues throughout life.
Babies born from mothers deficient in omega-3 have insufficient levels to support brain and eye development, while school age deficiency may manifest in attentional or behavioural problems. Through the teenage years, mood is likely to be affected by omega-3 deficiency (with particular risk of depression onset), while adults may be prone to anger and irritability. Older adults with low omega-3 brain levels are at higher risk of stroke, memory problems and early onset dementia. Low omega-3 levels at any age predispose individuals to higher risks for mental health issues such as depression, bipolar disorder and schizophrenia.
Omega-3 fatty acids
There are many different types of omega-3 fatty acids, therefore it is not so simple to say that you have a good intake of omega-3 fatty acids, as they are used very differently in the body and therefore have completely different health outcomes. The main differentiating feature of fatty acids is the ‘chain length’ – put simply, this is the amount of carbon atoms in the molecule. The more carbon atoms, the longer the chain.
Short-chain fatty acids
Short-chain omega-3 fatty acids are those found in plant sources such as linseeds and echium seeds, and are labelled as ‘essential fatty acids’ (EFAs) because they cannot be manufactured by the body, hence we must obtain them from our diet. It is from these short-chain fatty acids that our bodies derive the beneficial long-chain omega-3 fatty acids, requiring the use of enzymes in the body. The majority of short-chain fatty acids are utilised as fuel and therefore only some go on to be metabolised to the long-chain fatty acids.
It is now well-known that these conversions are not very efficient in many people and while the conversion from ALA to EPA and DHA is greater in women compared with men, on average the estimated conversion of ALA to EPA is between 0.2% to 8% and ALA to DHA around 0.05%. [1-4] Diets that are rich in LA (common in Western populations) not only decrease the conversion of ALA by as much as 40%,  but also influence the balance of pro-inflammatory to anti-inflammatory eicosanoids. This is simply because of the competition between ALA and LA for desaturation and elongation enzymes and competition between AA and EPA for COX and LOX enzymes.
Modern lifestyle and diet can have a huge effect on the efficiency of conversion, for example, zinc, vitamin B6 and magnesium are all required for the enzymes to support this process and are classified as ‘co-factors’. Deficiencies in these co-factors are common, however, due to high consumption of refined foods (whose natural micronutrients are stripped during the manufacturing process – for example, with white bread and white pasta) and low intake of nutrient rich foods such as fruit and vegetables, grass-fed meat and eggs from free range hens. Other factors which inhibit normal fatty acid metabolism include viruses, trans fats, alcohol, caffeine and stress.
Long-chain fatty acids
Long-chain fatty acids such as omega-3 EPA and DHA are found in fish and fish oil, seafood and a small amount in grass-fed meat and dairy. DHA plays a vital role in maintaining the structure and fluidity of our cell membranes, whereas the majority of functional health benefits associated with omega-3 fatty acids are due to the effects of the long-chain omega-3 EPA, as hormone-like by-products of EPA called eicosanoids are important anti-inflammatory substances, and are also required for optimal functioning of the brain. The body requires the long-chain omega fatty acids for health, so it is not advisable to rely solely on intake of short-chain plant-sourced fats due to poor conversion rates. Directly consuming long-chain fats in the diet (whether through food or via supplementation with fish oil) effectively by-passes the many enzyme-dependent and difficult steps of fatty acid metabolism. When EPA levels are low, DHA is ‘sacrificed’ from the cell membrane to ‘step in’ for EPA and so low EPA intake directly increases our rate of brain structure loss.
- Burdge GC: Metabolism of alpha-linolenic acid in humans. Prostaglandins, leukotrienes, and essential fatty acids 2006, 75:161-168.
- Burdge GC, Calder PC: Conversion of alpha-linolenic acid to longer-chain polyunsaturated fatty acids in human adults. Reproduction, nutrition, development 2005, 45:581-597.
- Burdge GC, Jones AE, Wootton SA: Eicosapentaenoic and docosapentaenoic acids are the principal products of alpha-linolenic acid metabolism in young men*. Br J Nutr 2002, 88:355-363.
- Burdge GC, Wootton SA: Conversion of alpha-linolenic acid to eicosapentaenoic, docosapentaenoic and docosahexaenoic acids in young women. Br J Nutr 2002, 88:411-420.
- Emken EA, Adlof RO, Gulley RM: Dietary linoleic acid influences desaturation and acylation of deuterium-labeled linoleic and linolenic acids in young adult males. Biochimica et biophysica acta 1994, 1213:277-288.
Omega-6 fatty acids
As with omega-3, the short-chain omega-6 fatty acids are also essential fatty acids as they cannot be made in the body and therefore must come from our diets. Linoleic acid (LA) is the essential short-chain omega-6 fatty acid, which is found predominantly in vegetable and nut oils such as corn, almond and sunflower oil.
The short-chain omega-6 fatty acids must also be converted to longer-chain fatty acids in the body, but the end products can vary and are either inflammatory or anti-inflammatory. This makes omega-6 fatty acids a little confusing. You may have read that omega-6 is anti-inflammatory and beneficial for balancing hormones, though you likely have also read that excess omega-6 can exacerbate inflammatory conditions such as cardiovascular disease and arthritis. Both are true, and to understand our requirements for omega-6, we must look to the ratio between omega-3 and omega-6 – it is the balance of these two omega families which is of most importance for health. More specifically, the ratio between omega-3 EPA and omega-6 arachidonic acid (AA) is the key biomarker for long-term health. Meat from animals fed on grains is the main source of AA in our diets.
To simplify the requirements of omega-6, consider that if omega-6 and omega-3 are balanced in a healthy ratio (for example,2:1), omega-6 is a healthy anti-inflammatory fatty acid, but if omega-6 is consumed in excess, (a ratio of 7:1 or higher), this can produce significant inflammation in the body due to the shift in end products from either family. Omega-6 consumption has certainly increased over the last few decades, partly due to farming techniques now that most animals are fed grains rich in omega-6, as opposed to their natural pasture-based diets, which were higher in beneficial omega-3. The use of refined vegetable oils in processed refined foods has also significantly increased our consumption of omega-6 fatty acids.
To ensure that you are getting a healthy balance of omega-3 and omega-6, as our diets are so much higher in omega-6, ensure that supplements are higher in omega-3 to keep inflammation regulated. The omega-6 gamma linolenic acid (GLA) sourced from evening primrose oil is anti-inflammatory, as long as it is balanced with omega-3 EPA, therefore a supplement containing both omega-3 EPA from fish and omega-6 GLA from evening primrose oil, with a higher dose of EPA, is a great way to get both omega-3 and omega-6 and ensure the by-products from both families are anti-inflammatory.
Omega-7 & 9
We sometimes forget that these other omega fatty acids exist, as there is so much emphasis placed on the wonderful health benefits of omega-3 fatty acids, and omega-6 to an extent, but being able to understand the importance and source of these other fatty acids is of course important.
Omega-7 and omega-9 are not considered to be essential fats as they can be manufactured in the body, though intake of these fats is still beneficial for health and may reduce our risk of cardiovascular disease. Consumption of these fatty acids is high in the ‘Mediterranean’ diet. Rich sources of omega-7 include macadamia nut oil, sea buckthorn oil and coconut oil. Omega-9 can be found in olive oil and rapeseed oil.
The most interesting point to note with the omega-7 and omega-9 fatty acids is that they are more heat stable than the delicate essential omega-3 and omega-6 fatty acids, which means that they make much more suitable oils for cooking with. Cooking omega-3 fats at a high temperature can ruin the fatty acid structure, making it difficult for our bodies to process and therefore no longer offering health benefits. Coconut oil on the other hand, and olive oil and rapeseed oil to a lesser extent, are much more heat-stable and therefore can be used in cooking while still providing benefits for our health.