We require two groups of essential fatty acids (EFAs) in our diet: the Omega-3 and Omega-6 families. The body requires both, but modern Western diets tend to provide excessive amounts of Omega-6 essential fatty acids, while intakes of Omega-3 essential fatty acids are generally low.
Significant levels of Omega-6 are found in seed oils (e.g. sunflower and corn oil) and of Omega-3 in oily fish, such as sardines, salmon and mackerel. The latter contain two types of Omega-3, EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). A major role of EPA is to support the heart and artery health, while DHA is indispensable in the structure of cell membranes throughout the body, and particularly those of the brain and the retina of the eye.
The Scientific Advisory Committee on Nutrition/Committee on Toxicity recommends an intake of 450mg EPA + DHA per day, but intakes in Western countries are much lower than this. See Figure 1. In contrast, we typically eat too much Omega-6.
A key action of Omega-3 is to ‘dampen down’ the inflammatory response in the body and maintain it within tolerable limits. Conversely, excessive intakes of Omega-6 essential fatty acids can cause excessive inflammation, damaging body tissues. It is important to keep a balance between our intake of Omega-3 and how much Omega-6 we eat because although inflammation is a necessary part of the body’s immune defences, it is becoming increasingly recognised as an important contributor to many chronic diseases, including cancer, heart disease  and diabetes. The maintenance of an appropriate inflammatory response is critical to disease prevention, and can be largely achieved by ensuring a healthy, balanced ratio of Omega-6 and Omega-3 essential fatty acids in all cells. Evidence for the health protective effects of ensuring a correct balance of intakes of these two essential fatty acids is still emerging, but it is thought that a healthy ratio is 50% Omega-3 going up to an optimum level of 70% Omega-3.
Since Omega-3 essential fatty acids are potent anti-inflammatory agents, they can be expected to be helpful for a wide range of inflammatory conditions.
* There is substantial evidence of benefit of them for treatment of rheumatoid arthritis,
* Based on evidence of reduced heart disease risk, many health agencies worldwide now recommend an increased intake of Omega-3 essential fatty acids,,
* The National Institute for Clinical Excellence (NICE) also recommends Omega-3 supplementation to those who have already had a heart attack
* Those with diabetes are at particular risk of heart disease, and have found benefit from Omega-3 supplementation, which improves insulin action , aids weight loss, and reduces blood triglyceride levels 
* Inflammation is also associated with several degenerative diseases of the brain, including Alzheimer’s and Parkinson’s
* That the brain can be subject to inflammation is a relatively new concept, and animal studies suggest that other brain-related disorders, including depression, anxiety and ADHD may also involve inflammation, indicating potential benefit from Omega-3 supplementation. Indeed, low blood levels of Omega-3 essential fatty acids are found to occur with depression, and fish oil supplementation has been shown to have anti-depressant effects. Furthermore, although low Omega-3 essential fatty acid status commonly occurs in Attention Deficit Hyperactivity Disorder (ADHD) with both adults and children, a definitive clinical study of supplementation is still awaited. However, pilot studies of Omega-3 essential fatty acids supplementation for children with learning difficulties have shown promising efficacy,(18, 19), and further clinical research in this area is underway.
An improved essential fatty acid balance can be achieved by reducing Omega-6 intake and increasing Omega-3 intake but it is helpful to know how much of each is in the body before starting so that optimum levels can be reached. Dietary ways of improving the balance include replacing seed oils in the diet with olive oil (which has a low Omega-6 content) and increasing intakes of Omega-3 essential fatty acids by eating oily fish and/or taking fish oil supplements.
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 Adam O et al. 2003. Anti-inflammatory effects of a low arachidonic acid diet and fish oil in patients with rheumatoid arthritis. Rheumatol Int23:27-36
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 De Caterina R et al. 2007. n-3 fatty acids in the treatment of diabetic patients: biological rationale and clinical data. Diabetes Care30:1012-26
 Mori TA et al. 1999. Dietary fish as a major component of a weight-loss diet: effect on serum lipids, glucose and insulin metabolism in overweight hypertensive subjects. Am J Clin Nutr70:817-25
 Nettleton JA & Katz R. 2005. n-3 long-chain polyunsaturated fatty acids in type 2 diabetes: a review. J Am Diet Assoc105:428-40
 Reynolds A et al. 2007. Oxidative stress and the pathogenesis of neurodegenerative disorders. IntRev Neurobiol82:297-325
 Parker G. 2006. Omega-3 fatty acids and mood disorders. Am J Psychiatry163, 969-978
 Young GS et al. 2004. Blood phospholipid fatty acid analysis of adults with and without attention deficit/hyperactivity disorder. Lipids39:117-23
 Burgess JR et al. 2000. Long-chain polyunsaturated fatty acids in children with attention-deficit hyperactivity disorder. Am J Clin Nutr71(1 Suppl):327S-30S
 Richardson AJ & Puri BK. 2002. A randomized double-blind, placebo-controlled study of the effects of supplementation with highly unsaturated fatty acids on ADHD-related symptoms in children with specific learning difficulties. Prog Neuropsychopharmacol Biol Psychiatry.26:233-9
 Sinn N & Bryan J. 2007. Effect of supplementation with polyunsaturated fatty acids and micronutrients on learning and behaviour problems associated with child ADHD. J Dev BehavPediatr.28:82-91
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