4. OMEGA-3 ESSENTIAL FATTY ACIDS

Omega-3 (you may sometimes see it written as n-3 or w-3) is the name given to a family of polyunsaturated fatty acids. The parent omega-3 - alpha-linolenic acid (ALA) - is described as 'essential' as, like vitamins, it must be obtained from diet. It is polyunsaturated and has 18 carbon atoms and 3 double bonds (18:3). However, from the point of view of human nutrition, the long-chain omega-3 fatty acids eicosapentaenoic acid (20:5)and docosahexaenoic acid (22:6) - EPA and DHA - are considered much more valuable as these are the forms the body requires. In theory, humans are able to synthesise EPA and DHA from dietary ALA, but in practice this process is inefficient. Scientists have therefore concluded that EPA and DHA should be obtained from diet. Oil-rich fish and supplements such as fish oil and cod liver oil, are the richest and most readily available sources. Other sources such as krill and fortified everyday foods like bread and fruit juices are in production in a minor way in various parts of the world.

 Like all fats, EFAs provide energy. Their calorific value is similar to other fats and oils but, unlike saturated fats, they have important health roles. In fact, as their name suggest, they are essential and must be consumed regularly as the body has limited storage for them.

Both of the important EFA families - omega-6 and omega-3 - are components of nerve cells and cellular membranes. They are converted by the body into eicosanoids, leukotrienes and prostaglandins - all of which are needed on a second-by-second basis by most tissue activities in the body.

 EFAs are involved in normal physiology, including:

 • regulating pressure in the eye, joints, and blood vessels, and mediating immune response

• regulating bodily secretions and their viscosity

• dilating or constricting blood vessels

• regulating collateral circulation

 • directing endocrine hormones to their target cells

• regulating smooth muscles and autonomic reflexes

 • being primary constituents of cell membranes

 • regulating the rate of cell division

 • maintaining the fluidity and rigidity of cellular membranes

 • regulating the inflow and outflow of substances to and from cells

 • transporting oxygen from red blood cells to the tissues

• maintaining proper kidney function and fluid balance

 • keeping saturated fats mobile in the blood stream

 • preventing blood cells from clumping together (blood clots that can be a cause of heart attack and stroke)

• mediating the release of inflammatory substances from cells that may trigger allergic conditions

• regulating nerve transmission and communication

 If the diet is deficient in either omega-6 or omega-3 long-term degenerative illnesses will result.

The human diet today is vastly different from that of our ancestors. For early mankind, hunting, fishing and food gathering were a survival imperative and as a consequence human beings evolved on 'natural' foods supplying a diet that was low in total fat and saturated fat, but contained a balance of omega-6 and omega-3 essential fatty acids. For most of the time humans have been on earth we have eaten foods containing omega-6s and omega-3s in a ratio of about 2:1. In recent centuries, the emphasis gradually moved away from hunting/gathering towards cultivating the land, but the greatest diet changes have occurred in the past 50 or so years. As a result of our increasing reliance on cereals, processed foods and, most significantly, vegetable oils and spreads, compounded by a decreased consumption of oily fish and grass-fed meat, today this ratio is about 10-20:1. Modern Western diets are therefore deficient in omega-3 fatty acids compared with the diet on which humans evolved and their genetic patterns were established. In simple terms, the best and richest sources of the omega-3 fatty acids are oil-rich fish and fish or cod liver oil supplements. This is because they supply the preferred omega-3's eicosapentaenoic acid and docosahexaenoic acid (EPA and DHA) that the body can use most readily.