Alfa-linolenic acid is an omega-3 fatty acid which is found in large amounts in vegetable oils, especially linseed oil and to some extent rape seed oil. It is assumed to have health promoting effects but more studies are required to certify those effects. In this project enzymes are used to prepare alfa-linolenic acid containing lipids starting from natural raw materials. The physiological effects of those lipids will be evaluated in animals and humans. The aim is to make a lipid in which the health promoting effect of alfa-linolenic acid is optimized. Because of the sensitivity of alfa-linolenic acid to oxidation, proper protection with antioxidants will also be of importance. So far, combinations between butter oil and a vegetable oil, linseed or rape seed oil, have been made by enzymatic transesterification. Analysis has shown the formation of several new combinations of fatty acids in the triglycerides.