The richest sources of EPA and DHA, however, are cold-water fish, particularly salmon, herring, anchovies, and sardines. Halibut, mackerel, and tuna also have Dmega-3s, however I recommend eating them no more than once a month due to concerns about possible mercury contamination.
I really believe, wild fish are usually better than farm-raised fish since farmed fish are generally fed corn and grains, raising their omega-6 content. Also, instead of living far out to sea, farm-raised fish live near shore and so are more prone to be contaminated with man-made toxins, for example PCBs (harmful compounds found used as insulating and cooling fluids, which are extremely slow to biodegrade), I would recommend limiting intake of farmed fish to no more than once per month. Supplements can be purchased in health-food stores and online in liquid or gel capsule form. The liquid gives a higher concentration per dose, is usually less costly, and now is available flavoured with lemon or orange to lessen the fishy taste. However, I find that most people prefer capsules, which have no taste.

For many people, fish oil (especially in liquid form) triggers unpleasant bouts of belching. To reduce this, take your fish oil with meals. Should the problem persists, buy enteric-coated fish oil capsules-their harder casing keeps the capsule from opening until it reaches the small intestine, preventing the stomach gassiness that creates burping. Fish oil capsules often come in l,000 mg doses but this refers to the weight of the oil, not to the exact amount of DHA and EPA they supply. Examine the label to see how many capsules you have to take daily to get the standard dose of 500 mg to 1,000 mg of combined DHA and EPA. Those with existing arthritis or cardiovascular disease may need up to 3,000 mg of combined EPA and DHA.

It is always good to take vitamin E on the same day as fish oil. It prevents oxidation of vitamin E in the body and fish oil may lower the body’s vitamin E levels.
In a more direct research of fish intake, team 36 scientists who studied mortality data from 36 countries verified that life expectancy is much longer in those countries where people get a lot of fish in their daily diet. Men and women who eat more fish have a lower risk of early death from all types of illnesses, particularly stroke and heart disease.

Essential fatty acids form a group of hormone-like messengers generally known as prostaglandins. The omega-3 fatty acids as found in fish oil-helped along by the EPA and DBA in the fish-tend to reduce inflammation, thin the blood, and balance the Immune system.

In the immune system, EPA is apparently particularly important for its anti-inflammatory effects, so it’s useful to people who suffer from arthritis. DHA is very important for the proper development and function of the brain because your brain cells need it to transmit electrical impulses efficiently. It’s not surprising, therefore, that a DHA deficiency can cause memory, behavior, and learning problems.

Some studies have also revealed that supplementing infant formula with DHA, can enhance children’s IQ. Interestingly, it’s also essential for mood regulation, and research indicates that a deficiency can lead to depression. The DHA present in fish oil also seems to calm down hyperactive children. It’s also needed for proper retina development for infants.