The 18 carbon α-linolenic acid has not been shown to have the same cardiovascular benefits as DHA or EPA.[13] Currently there are many products on the market which claim to contain health promoting 'omega 3', but contain only α-linolenic acid (ALA), not EPA or DHA. These products contain mainly higher plant oils and must be converted by the body to create DHA and therefore considered less efficient. DHA and EPA are made by microalgae that live in seawater. These are then consumed by fish and accumulate to high levels in their internal organs. If a person has ethical concerns about killing fish, or is concerned about mercury and oceanborne contaminants in fish, DHA can be produced directly from microalgae as a vegetarian source. People with certain circulatory problems, such as varicose veins, benefit from such supplements containing EPA and DHA which stimulate blood circulation, increase the breakdown of fibrin, a compound involved in clot and scar formation, and additionally have been shown to reduce blood pressure.[14][15] There is strong scientific evidence that n−3 fatty acids reduce blood triglyceride levels[16][17][18][19] and regular intake reduces the risk of secondary and primary heart attack
