Fats are chemicals made up of long chains of carbon atoms surrounded by hydrogen atoms. When a carbon chain is attached to the maximum number of hydrogen molecules that it can hold, it is called a saturated fat.

When one or more carbon atoms are joined by double bonds, the fat is unsaturated. These double bonds allow the molecules to be easily broken down and used for a variety of essential body functions.

Omega-3 fatty acids are a group of polyunsaturated fats that have three double bonds between different carbon atoms, and that bond is represented by the Greek letter omega.

Fish oils are lipids found in cold water fish and other marine life such as phytoplankton. FIsh oils (DHA and EPA) are rich sources of long chain polyunsaturated fatty acids of the omega 3 type.

Docosahexaenoic acid contains 22 carbon atoms and six double bonds (DHA; C22:6n-3)
Eicosopentaenoic acid contains 20 carbon atoms and five double bonds (EPA; C20:5n-3)

EPA and DHA have several actions in a number of body systems. EPA is the precursor to series-3 prostaglandins (PG), the series-5 leukotrienes (LT) and the series-3  thromboxanes (TX). These compounds (eicosanoids) have anti-inflammatory and anti-atherogenic properties.

Cell membrane fluidity is essential for proper cell functioning. DHA is a vital component of cell membranes especially thoses in the brain, retina and heart.

Alpha-linolenic acid is also a source of omega 3.
This intermediate chain polyunsaturated fatty acid contains
18 carbon atoms and three double bonds (ALA; C18;3n3).

Flaxseed oil is a potent source of alpha-linolenic acid. The Mediterranean diet, high in ALA appears to lower the risk of coronary artery disease and certain types of cancer. ALA is metabolized to eicosopentaenoic acid (EPA). As such, flaxseed oil also generates anti-inflammatory, anti-thrombotic and anti-proliferative activities.

While Omega 3 is grouped together like a family, the structural formulas of omega 3 are different. DHA, EPA and ALA each have unique cellular and molecular effects on the body. DHA most specifically helps prevent atrial and ventricular arrhythmia. EPA and ALA help to inhibit inflammation and blood clot formation.

Sources:
Physician Desk Reference for Nutritional Medicine 2004
www.pdrhealth.com

American Journal of Clinical Nutrition 2000;71;171S-5S
William E. Connor