Linolenic acid. Computer model of a molecule of linolenic acid, one of the essential fatty acids. The colours represent the constituent atoms: green (carbon), yellow (hydrogen) and red (oxygen). Linolenic acid is also known as cis, cis, cis- 9, 12,15-octadecatrienoic acid, and has a straight chain structure of 18 carbon atoms with three double bonds. Linolenic acid is found in linseed oil, and is used in a variety of food products including margerine, where it is one of the unsaturated fats. Deficiency of essential fatty acids can cause skin problems, weight loss and irregular oestrus.