The Certificate of Analysis or COA is an evaluation conducted by an independent laboratory to check for contaminants, oxidation and omega3 content. If all manufacturers posted the result of that analysis on their websites, it would be easy to compare. But, most manufacturers fear what you would learn.

Mercury, dioxins and PCBs are some of the things that they don't want you to know about. Oxidized or rancid oils are another.

Oxidation or spoilage begins as soon as the fish are pulled out of the water. If they are not properly stored or if they are left on the dock to rot in the sun, the level of oxidation becomes extremely high. Oxidation is responsible for those fishy tasting burps that you get. The best fish oil supplements don't cause them. The manufacturer guarantees it.

Some manufacturers believe that a little bit of heavy metals like mercury and cancer-causing dioxins won't hurt you. But, in the purest oils, there are no detectable levels of those contaminants. The COA proves it.

When it comes to the omega3 content, the COA will show how much total omega3s are present in each capsule, as well as individual amounts of DHA, EPA and DPA. DHA is essential for the growth and functional development of the human brain. It is required for maintenance of normal brain function in adults. Its absence in the diet leads to learning deficits and depression.

DHA deficiencies are also associated with Attention Deficit Disorder, cystic fibrosis, aggressive behavior, cognitive decline and Alzheimer's. It has a positive effect on high blood pressure, arthritis, type II diabetes and some types of cancer. So, obviously, the best fish oil supplements contain large amounts of DHA.

EPA has proven benefits in heart disease and inflammatory disorders. DPA is believed to contribute to overall cardiovascular health. Research is currently ongoing concerning these other two essential fatty acids. But, the benefits of DHA have been well understood for quite some time.

The best fish oil supplements provide at least 280mg of DHA per capsule, at least 120mg of EPA and at least 50mg of DPA. The total omega 3 content in 1000mg of oil is 500mg. Some manufacturers do not list the omega 3 content and most do not break it down into individual omega3s. Of those that do, only a few have an independent COA to back up their statements.

The benefits to your health will be numerous if you select an excellent supplement. One of the first things that you should notice is an improved ability to concentrate. If you've been feeling a little depressed, you should notice an improvement in your mood. If your joints feel a little achy, you should notice greater flexibility.

Those are just some of the things that people have noticed when they buy and take the best fish oil supplements. Now, you know how to find yours.