Fish Oil - In terms of biochemistry, what are fish oils?

Fat is a molecule used to store energy, build cell membranes, and many other functions. The molecules that make up fat are mostly fatty acids, which are long chains of carbon atoms with a carboxyl group on the end. The fatty acids are divided into two groups, saturated and unsaturated fats. If the carbon atoms are connected by single bonds, the bonds are "saturated" with carbon atoms. This is the kind of fat found in butter, red meat, and pork. Unsaturated fatty acids have double bonds between some of the carbon atoms. Many of these unsaturated fatty acids are not synthesized by humans, and are required in the diet for good health. Humans do not metabolize unsaturated fats very well, and most polyunsaturated fatty acids (with more than one carbon carbon double bond) are not digested completely by humans. They taste good, but do not make a person fat, thus the preference for vegetable oils that contain polyunsaturates.

Omega Fatty Acids - Omega fatty acids have double bonds. The carbon atom farthest from the carboxylic acid end is called the omega carbon, the last one. So omega 3 fatty acids have a double bond starting in 3 carbons from the end, and omega 6 fatty acids have the double bond in 6 carbons from the end. Omega 6 fatty acids [like arachidonic acid] produce pro-inflammatory eicosanoids including prostaglandin E2, thromboxane A2, and leukotriene B4, which cause inflammation, which has been connected with heart disease. Omega 3 fatty acids, particularly EPA [eicosapentaenoic acid] and DHA [docoshexaenoic acid], which are found in fish oil tablets and fish, produce antiinflammatory products.Standard fish oil tablets contain 180 mg EPA and 120 mg DHA.

Note that other omega-3 oils from plant sources such as flaxseed are shorter. Fish get DHA and EPA from blue-green algae. Shorter omega-3 fatty acids not specifically from blue-green algae or fish are not effectively made into EPA and DHA by humans. So it is hazardous to rely on flaxseed for the omega-3 fatty acids needed for your brain. If you are a vegetarian, get a blue-green algae supplement that specifies the EPA and DHA content, because those are the critical fats we need.