The practice of giving cod liver oil began when the smoke-filled skies of nineteenth-century England deprived youngsters of exposure to the sun. Without sun, their bodies couldn't make vitamin D, and they developed rickets. Because cod liver oil contains large amounts of vitamin D, it cured rickets and made a great contribution to public health. Today, however, other constituents of cod liver and other fish oils have become of interest: the omega-3 fatty acids. Subsequent investigation found that the omega-3 fatty acids found in fish oil can lower blood triglyceride levels, thin the blood, and also decrease inflammation in various parts of the body. These effects, as well as others, may explain many of fish oil's apparent benefits.

Typical dosages of fish oil are 3 to 9gm daily, but this is not the upper limit. In one study, participants ingested 60gm daily. Often there is a digestive disturbance that prevents some people from using fish oils. There are preparations which are coated to overcome this difficulty.

The most important omega-3 fatty acids found in fish oil are called EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). In order to match the dosage used in several major studies, one should probably take enough fish oil to supply about 1,800mg of EPA and 900mg of DHA daily. Certain conditions require a predominance of EPA while others require DHA. Since they compete with each other, careful attention must be paid to their ratio in those conditions which are discussed elsewhere.

Some manufacturers add vitamin E to fish oil capsules to keep the oil from becoming rancid. Another method is to remove all the oxygen from the capsule.

Cod liver oil preparations are much easier to take these days than when we were growing up. They come in flavors such as lemon and orange, making them very easy to take. However, buying a bottle of cod liver oil would seem to be much less expensive than taking fish oil capsules. A tablespoon of flavored cod liver oil may have 500mg of EPA and 350 of DHA. There may be 23 servings in a 12 ounce bottle of cod liver oil. Capsules vary in their EPA / DHA content but may average only 1/4 or 1/5th of the amount in a tablespoon of cod liver oil. Keeping this in mind may help determine if one form turns out to be better priced than the other.

For example, if a bottle of cod liver oil is $12.00, then it would take at least 100 plus capsules to provide the same amount of EPA and DHA. If the capsules cost more than $12.00, then the bottle of cod liver oil would be a better buy. You will need to make your own caculations based upon the amount of EPA and DHA in the capsules you are considering.

Krill oil is another very good source of EPA and DHA and is becoming more readily available as a valuable source of these Omega-3 fatty acids. It is also high in protective phospholipids and potent antioxidants, which make it an ideal source of Omega-3 essential fatty acids, which are subject to rancidity. Fish oil and flax are weak in antioxidant content. Further, the phospholipids found in krill oil aid in the absorption of the essential fatty acids which are present. So, fish oil is good, but krill oil is even better, though more expensive.