By Mary Kate Keyes, M.S.
You may have noticed that new products — from yogurts and cheeses to bread and eggs — touting their omega-3 content are popping up on grocery shelves. Omega-3 fatty acids are in the spotlight recently because there is scientific evidence to suggest many of us are not getting enough of these polyunsaturated fatty acids. But contrary to what advertisers will have us believe, omega-3s are not the only fatty acid that is good for us.
Your body needs omega-3, -6 and -9 fatty acids for survival. Fortunately, the body makes omega-9 fatty acids when needed. Omega-3 and -6 cannot be made because humans lack the necessary enzymes. Therefore it is essential that we get these two nutrients from the foods we eat. This is why omega-3 and omega-6 fatty acids are referred to as "essential fats."
Your body needs both omega-3 and omega-6 fatty acids to maintain healthy cell membranes, and to build many important molecules. Omega-3 fatty acids:
These three fatty acids are called polyunsaturated fatty acids. Many (poly) of the carbons that make up the fatty-acid molecule are unsaturated. This means they do not have a hydrogen atom attached to them. The numbers -3, -6 and -9 come from special bonds within the fat molecule.
One of the best reasons to consume polyunsaturated fatty acids is because they replace the "bad" fats — saturated and trans fats — found in butter and stick margarine. Polyunsaturated fats have been shown to decrease LDL cholesterol, or the bad cholesterol, which reduces your risk of developing coronary heart disease.
As important as these fatty acids are in your diet, evidence shows that it is the ratio of omega-6 to omega-3 fatty acids that is most important.
Humans evolved with a diet rich in both omega-6 and omega-3 fatty acids. Our ancestors ate a varied diet that contained almost equal amounts of both fatty acids. Unfortunately, the modern diet is not so well-rounded.
Today in North America, most individuals' diets have an omega-6 to omega-3 ratio of around 10:1. In other words, we get 10-times as much omega-6 as omega-3 fatty acids in our diets. In many cases this ratio is even higher. This is simply because omega-6 fatty acids are in so many of the foods we eat: vegetable oils, poultry, eggs, cereals and bread to name a few. So while we are getting plenty of healthful omega-6 fatty acids, we're often missing the important omega-3 fatty acids.
For most people, eating fish twice a week is the best way to get enough omega-3 fatty acids in the diet. Fish contain omega-3s in the two forms your body can use most readily: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).
If, however, the catch of the day doesn't entice you, there are other ways to get omega-3 fatty acids. Walnuts and flaxseed, for example, contain another form of omega-3 fatty acid called alpha-linolenic acid (ALA). Although ALA is not converted well to the more user-friendly EPA and DHA forms, walnuts and flaxseed are healthful foods nonetheless.
Adults should try to consume about 1/2 to 1 gram of EPA and DHA each day, or 5 to 10 grams of ALA each day.
Mary Kate Keyes, M.S. is a dietetic intern at Brigham and Women's Hospital. She received a B.A. in Biology from Merrimack College and an M.S. in Nutrition Communication from Tufts University Friedman School of Nutrition Science and Policy.