Winter 2000 Issue — The Health Benefits of Omega 3 Fatty Acids

Alison Evennett

Health and Nutrition Manager, Denofa

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Cod liver oil has long been taken as a dietary supplement, traditionally for its vitamin A and D content, but today perhaps more importantly as a course of very long chain omega 3 fatty acids. In many countries the majority of the population do not meet current recommendations for these fatty acids and advice to eat more oil-rich fish such as salmon, mackerel and sardines is difficult to follow. Given the increasingly strong evidence about the health benefits of very long chain omega 3 fatty acids there is clearly a major opportunity to provide acceptable sources such as dietary supplements and good tasting functional foods.

What are omega 3 fatty acids?

There are two families of polyunsaturated fatty acids (PUFAs) — omega 6 and omega 3 fatty acids. The omega 6 group includes the essential fatty acid linoleic acid and its longer chain derivatives e.g. arachidonic acid. The omega 3 group includes alpha linolenic acid and the very long chain fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Alpha linolenic acid is found in foods such as seed oils (e.g. linseed and soya), nuts, ruminant meats, and dark green leafy vegetables. EPA and DHA are found naturally in oil-rich fish and fish liver oils and can also be synthesised in the body from alpha linolenic acid. The capacity of the body to synthesis EPA and DHA is however a current subject of scientific debate. The balance between the level of omega 6 and omega 3 fatty acids in the diet appears to be very important. High intakes of omega 6 fatty acids as found in many western diets today, limits the body's ability to synthesis the very long chain omega 3 PUFAs.

Benefits of very long chain PUFAs

Increasing research is confirming the importance of EPA and DHA and showing that they may have a positive influence on more conditions than previously thought. Potential health benefits of omega 3 fatty acids include their effect on inflammatory conditions such as rheumatoid arthritis, with studies showing that supplementation with fish oil reduced pain and stiffness in sufferers. Interesting new studies have linked increased intakes of very long chain omega 3 fatty acids with improvements in insulin resistance, an early indicator of adult onset diabetes, with mental disorders such as depression and schizophrenia and with the prevention of relapses in multiple sclerosis.

More established though is the evidence that oil-rich fish can substantially reduce the risk of a fatal heart attack. The body of evidence has reached the stage where in the United States the FDA are currently reviewing whether to permit a health claim in this area. The effect of omega 3 fatty acids on risk of coronary heart disease (CHD) has been shown in a considerable number of studies, and the risk of a fatal heart attack has been seen to be lower in those who had even one serving of fish per weeks compared to those who ate none. This protective effect is also achieved with fish oil supplements — in a recent trial, supplements of 850mg of EPA and DHA were given to patients with known heart disease.(1) The results after 3.5 years showed that those taking supplements had a 20% lower total mortality than the control group and that the incidence of sudden cardiac death was reduced by 45%.

These are probably several mechanisms by which oil-rich fish reduces the risk of CHD. It is generally agreed that the very long chain PUFAs are active components and that they have an effect on a number of CHD risk factors: on blood pressure, plasma lipid pattern particularly in reducing triglycerides. blood clotting, arrthymia and inflammation. One route of influence is via EPA in the production of eicosanoids, compounds that influence the constriction of blood vessels, blood clotting, and the immune and inflammatory response. Eicosanoids are synthesised from both omega 6 and omega 3 fatty acids but those derived from the omega 3 family are less active. Shifting the balance to more eicosanoids from omega 3 fatty acids reduces the tendency of the blood clot, and causes less constriction of blood vessels, both of which contribute to lowering the risk of CHD. This favourable change can be produced by increasing omega 3 or reducing omega 6 fatty acid intakes.

Infant development

The importance of omega 3 fatty acids for foetal and infant development is also well established. DHA is a major component of the brain, retina and nervous system and the foetus obtains its supply from the mother, particularly during the period of very rapid growth during the last three months of pregnancy. After birth, breast-feeding infants obtain DHA from milk but infant formula has traditionally not contained DHA. Pre-term babies appear not to have the capacity to synthesise sufficient very long chain fatty acids for optimal growth from alpha-linolenic acid, so most pre-term infant formula milks are now fortified with DHA. The question about whether infant formulas for full-term infants should also be fortified is still under discussion but a recent workshop concluded that all formulas should have both DHA and arachidonic acid (the long chain polyunsaturated fatty acid from the omega 6 family) added.(4)

Recommendations for omega 3 fatty acid intake

Several countries have introduced specific recommendations for intake of the very long chain PUFAs. In the UK the Department of Health recommend intakes of long chain omega 3 PUFA should be at least 1.5g per week, which would mean eating oil-rich fish once to twice a week.2 The British Nutrition Foundation's Task Force on unsaturated fatty acids suggested a desirable population intake of 0.5% energy from very long chain PUFAs which would be equivalent to about 2-3 servings of oil-rich fish per week.(3)

A workshop in America in 1999 convened experts in the field to discuss the "Essentiality and Recommended Dietary Intakes for omega 6 and omega 3 fatty acids". The group concluded that for adults the Adequate Intake for DHA and EPA should be 0.3% energy i.e. 0.65mg per day for a 2000kcal diet. Pregnant and lactating women should ensure that they have at least 300mg DHA per day as recognition of the importance of these fatty acids in infant development. The group also recommended intakes of of 1% energy from alpha linolenic acid, and that omega 6 fatty acids intakes should be decreased i.e. use less plant oils rich in linoleic acid such as sunflower oil.

Changing the diet

In many countries, only a small percentage of the population reach the recommendations for very long chain omega 3 fatty acids. In the UK only a third of people eat oil-rich fish on a regular basis and even these people eat only an average of one small portion each week. Persuading people to change their diet to include more fish is difficult — many people do not find it acceptable — so supplements or foods with added fish oils are potentially an important means of increasing intakes.

Adding fish oil

In practice, fortifying foods with fish oil can be difficult because of the polyunsaturated fatty acids which are readily oxidised. Preventing this oxidation and thereby minimising the development of "fishy" flavours is key to developing acceptable products. Starting with a "good oil" is an important factor — oils with a low content of oxidation products initially tend to have a better taste and are found to be preferred by consumers in taste panels. Starting with very fresh fish raw materials, and using the new "cold pressing" technology which keeps the oil at a low temperature results in a product with lower peroxide and anisidin values, and better stability and taste than oils produced with other processes.

The challenge is still however to use these oils to make appealing products and to educate consumers about the importance of choosing these foods. To achieve this successfully requires partnerships between ingredient suppliers, manufacturers, and retailers for product development. Equally important are a regulatory environment that permits clear messages on products, and good relationships between industry and health professionals to present consistent messages to the consumer about the importance of omega 3 fatty acids for good health.

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