Omega-3s: the oily truth by Suzannah Olivier

Fish oils (omega-3s) have benefits for a huge variety of conditions - boosting brainpower, tempering arthritis, protecting against some cancers, benefiting eczema and sometimes asthma
The long-chain polyunsaturated fatty acids (DHA and EPA) found in oily fish have a particularly flexible chemical structure which allows them to be absorbed in to cell membranes and nervous tissue.

Because of this unique structure they're very important for human health. Their role in curbing inflammation is probably the reason why they can protect against a wide range of advertisement allergies, inflammatory diseases such as arthritis and irritable bowel, some cancers, heart disease and even Alzheimer's disease.

Additionally, EPA has blood-thinning properties, which give further cardiovascular protection. Some researchers believe that we evolved on a diet uniquely high in these fatty acids, which then permitted our brains to develop in such a sophisticated way.

Children in particular may benefit from these fatty acids early in life when they're being incorporated into brain and eye structure. So important are these omega-3s to babies that human breast milk is particularly rich in them. Research is also showing that learning and behavioural conditions, such as dyslexia, dyspraxia and Attention Deficit Hyperactivity Disorder (ADHD), can be significantly improved in some children by supplementing omega-3s.
The best sources of omega-3s:

Fish with high amounts of omega-3 include tuna (fresh), mackerel (fresh or smoked), salmon (fresh or smoked), sardines (fresh or canned), herrings, anchovies, pink trout, kippers, mullet, sprats, sturgeon and eel.

Fish with medium amounts include halibut, smelt, shark, oyster, swordfish and trout.
Fish with low amounts include tuna (canned in any way as it is defatted before canning), bass, bream, cod, coley, prawns, mussels, haddock and of course, fish fingers and fish and chips.
We're advised to eat two portions (150g/6oz) of fish weekly, with one portion being oily fish. Because of problems with pollution in fish higher up the food chain, pregnant women are advised to avoid shark, swordfish and marlin, and limit tuna to one medium steak or two cans per week. Many people prefer to get their omega-3s from fish oil supplements (which are made from fish muscle meat or krill) rather than cod liver oil, as there is more risk of environmental contamination in liver oils. Cod liver oil is high in vitamin A and should be avoided if planning to conceive - too much can adversely affect the developing foetus.

Plant sources Plant sources of omega-3 fatty acids can be turned, in the body, into the same long-chain structures as those found in oily fish, but this process is slow and not necessarily very efficient in some people (most likely those with allergies or learning difficulties).

Although fish remains the best source of these fatty acids, fish consumption has dropped by 50 per cent in the last fifty years.

Interestingly omega-3s are the most abundant fatty acids on the planet - found in all grasses and leaves. The list of plant sources of omega-3 fatty acids is not very long:

enriched eggs
organic milk has two-thirds more omega-3s than ordinary milk
flax oil and linseeds (flax seeds)
canola (rape) oil
pumpkin seeds or oil
walnuts and walnut oil
green, leafy vegetables