Essential fatty acids are classified into two basic groups which are omega-3 and omega-6 fatty acids. Most of us have heard that we should try to stay away from omega-6 fatty acids. In principle omega-6 fatty acids are just as essential as omega-3 fatty acids. It’s just that the omega-6 variety is very plentiful in our modern diet, and it is not only the presence of these molecules in our diet what matters, but the ratio in which they are present. The optimal ratio of omega-6 to omega-3 fatty acid has been estimated to be 1:1 or 3:1, but the actual ratio we tend to consume is closer to 15:1. In other words, we are getting too much omega-6 and not enough omega-3 fatty acids.
So we agree that we need to consume more omega-3 fatty acids. Where do these fatty acids come from? Is it true we can get them from vegetable sources like flax seed? The two omega-3 fatty acids that are considered essential for humans are EPA (eicosapentaenoic acid), with 20 carbon atoms and DHA (docosahexaenoic acid), which has 22 carbon atoms. Both are polyunsaturated, meaning that they have several double bonds in the carbon backbone. EPA has five double bonds while DHA has six. Flax seed and leafy green vegetables contain an omega-3 fatty acid, but it is neither EPA nor DHA. Its name is ALA (alpha linolenic acid), and it has only 18 carbon atoms.
In principle it is possible to convert ALA to EPA and DHA in the human body, but the efficiency of this process is very limited, especially for DHA. Other animals, like cows and chickens, are much more efficient at converting ALA to EPA and DHA (birds, in general, are better at it than mammals), so they are given a source of ALA and then humans eat them to obtain a food source enriched in omega-3 fatty acids. It’s fine for a food has both omega-6 and omega-3 fatty acids as long as they are present in the proper ratio. Chickens fed flax seed produce eggs that are greatly enriched in DHA. Grass-fed cattle produce beef with a much more optimal essential fatty acid ratio than corn-fed cattle.
The best animal source of omega-3 essential fatty acids is fish and fish oil like krill oil. Like land animals, fish cannot really make their own. They obtain theirs from microalgae in plankton, which do have the ability to manufacture these fatty acids. The microalgae are consumed by the smallest fish and by the larvae of corals and shellfish that also live in the plankton layer. These are eaten by larger fish, and so forth, until we consume the essential fatty acids not only in large fish like tuna and cod fish, but also smaller ones like sardines. Fatty fish that live in cold water tend to have the highest concentrations of omega-3 fatty acids in their own fatty tissue and in their livers.
Our choices for obtaining omega-3 fatty acids thus range from fish to grass-fed beef to organic chicken and eggs. We can also buy nutritional supplements. Cod liver oil has both EPA and DHA fatty acids, and also contains fat-soluble vitamins. Fish oil has the fatty acids, but no vitamins. Microalgal oil is derived from microscopic, single-celled microalgae like Schizochytrium, and is especially rich in DHA. We can take flax seed oil, but keep in mind that the conversion rate is inefficient, and becomes even less efficient as we get older. By paying attention to the fats in our diets and making smart decisions about the sources of our food (grass-fed vs corn-fed), we can optimize our ratio of essential fatty acids.