The science behind dietary omega-3 fatty acids
January 15, 2008
Marc Surette is Professor and Canada Research Chair in Cellular Lipid Metabolism, Département de Chimie et Biochimie, Université de Moncton, Moncton, NB
CMAJ • January 15, 2008; 178 (2)
Our diet contains a complex mixture of fats and oils whose basic structural components are fatty acids. We generally consume at least 20 different types of fatty acids, which are classified as saturated, monounsaturated and polyunsaturated. Fatty acids have many fates in the body, including β-oxidation for energy, storage in depot fat or incorporation into phospholipids, which form the major structural components of all cellular membranes. Not all dietary fatty acids are created equally.
Because humans do not have the enzymatic machinery required to synthesize omega-3 fatty acids, they must be obtained from the diet (termed "essential fatty acids"). Even among dietary polyunsaturated fatty acids, there are different families of compounds, and this is at the heart of the difference between omega-3 fatty acids and other dietary lipids. Omega-3 fatty acids generally account for a small fraction of the total daily consumption of fatty acids in Western societies.
Fish such as tuna, trout and salmon are especially rich sources of these fatty acids. Fish-oil supplements are also a rich source, as they typically contain 30%–50% omega-3 fatty acids by weight. Small quantities of omega-3 fatty acids are naturally present in meats like beef, pork and poultry. Despite containing small quantities of omega-3 fatty acids, meats contribute to the overall intake of these fatty acids simply because of the large amounts consumed in Western societies.