Oil from the liver of a cod, in its natural form, and concentrated fish oil are rather different re purity and amount of important components. Cod fish oil is basically from the liver of fish. Standard grade oils are extracted from the fish itself.

Let's talk about natural fish oil first. Standard grade generally contains low levels of omega-3 trans-acids like DHA and EPA. Cod fish oil comes from the liver of fish, that's why it's also known as cod liver oil.

This oil does contains a high amount of DHA and EPA just like concentrated oil. The fish used to get cod liver oil is generally caught in soiled, polluted waters, which can contain exaggerated levels of pollutants.

Concentrated or ultra refined oil, just like cod liver oil, has raised levels of DHA and EPA. It does not contain vitamins An and D, which eliminates the chance of vitamin overdose.

So you wish to make sure to buy pure cod liver oil when your looking to buy your next fish oil supplement