Omega-3 Fatty Acids
Fish and Flax Oil
Fat in the body comes in many varieties. As many of you know by now, we have gotten away from thinking of all fat as bad. There are good fats and bad fats. The fats that are harmful when present in excess in the diet are saturated fats such as butter, cream, and the fats present in many cheeses and meats, and so-called "trans" fat, which is produced primarily when healthier fats are "hydrogenated" in a process that makes them change from their naturally liquid state to a more solid state that makes products such as cookies store better over the long term. "Monosaturated" fats include olive oil and canola oil, and these are generally healthy (although remember that all fats, good or bad, are 120 calories a tablespoon!). And at the other end of the health scale for fats and oils are so-called "omega-3" fatty acids which largely includes fish oil and flax oil.
What have we learned about omega-3 oils?
They are highly beneficial. Many observational studies have shown that a diet higher in fish is associated with better health, and in particular with a lower rate of death from coronary heart disease. More recently a number of carefully carried out controlled trials [Want to know more about controlled trials? Click here.] have confirmed the earlier findings, and have shown that for patients who already have heart disease, taking approximately 1000 mg of omega-3 fatty acids daily produces a one third reduction in death rates, a truly remarkable outcome from a product that is inexpensive, readily available, and safe. It turns out that it doesn't take a lot to produce this effect - the equivalent of two or three salmon meals a week will do it.
Should everyone take fish oil supplements?
Well, I believe that the evidence is sufficient to recommend that anyone who has known coronary heart disease or is at high risk for coronary heart disease (for example by being diabetic or a smoker) should ensure an adequate intake of omega-3 fatty acids, and for the high-risk individual this is perhaps best done with supplements. But I do not believe that everyone should be taking supplements. For healthy people, eating fish a couple of times a week is a reasonable thing to do. But understand that vegan vegetarians - persons who eats no animal products - are at very low risk despite not eating fish because their overall diet is exceedingly healthy.
The fish that have such beneficial oils are largely those that live in cold waters. These include salmon, mackerel, sardines, tuna and herring, among others. For more information and a table giving omega-3 content of various fish click here, and for those who really want more information a good article is at http://circ.ahajournals.org/cgi/content/full/106/21/2747. Be aware that fish that have been extensively processed such as those in a McDonald's fish sandwich are not beneficial, and that farmed fish contain variable amounts of these beneficial oils depending on what they are fed.
If you do take supplements, it is important to know how to read the labels. When you pick up a bottle of fish oil capsules it is likely to say "Fish Body Oil 1000 mg". But this is the weight of the capsule, and not the content of omega-3 fatty acid. On the side of the label you will find a listing of the fatty acid content. To make things more confusing, you need to know that there are two fatty acids in this category: eicosapentaenoic acid (EPA) and docosahexanoic acid (DHA). The content of these two substances is often given separately and then added together. Often you will find that each capsule has 500 mg of omega-3 fatty acid, as is present, for example, in Trader Joe's capsules. But you will also find that some contain only 300 mg and you would then need to take three a day.
Consumer Reports has reviewed fish oil capsules and found that every one they tested contained the amount of omega-3 fatty acid that was listed on the label, and that none contained any toxic products such as mercury.
There is a second use for a omega-3 fatty acids, and this is their value in reducing high blood triglyceride levels. But in contrast to the relatively small amounts of omega-3 fatty acid needed for the cardiac benefit, it takes much larger amounts to lower triglycerides, and we commonly recommend at least a tablespoon of liquid oil daily. A tablespoon of fish oil (I took cod liver oil as a child!) is not necessarily pleasant, and here we switch to flax oil. Flax oil is a vegetarian form of fish oil in that flax oil is 50% omega-3 fatty acid, far higher in such content than the next closest oil, canola oil, which contains approximately 10% omega-3 fatty acid. I can already hear you saying "Why take the liquid? Can't I just take more capsules? Well you can, but the problem is that 1 tablespoon is the equivalent of 12 capsules!
Once you open a bottle of flax oil, it needs to be kept refrigerated or it can spoil. Flax oil has a slight nutty flavor and if it doesn't taste good if may mean it has gone rancid. Of course, the problem with keeping it in the refrigerator is that you have to remember to take it out and use it. The best time to take it is before the evening meal has been eaten as it will slightly blunt your appetite and you won't end up taking in an extra hundred calories.
For a much fuller discussion of triglycerides see the separate article here.