Omega-3 Fatty Acids and Your Health by Cheryl Winter, M.S., R.D., R.N.Overview:
While you know “omega” as
last letter of Greek alphabet, and meaning, “the end,” it is doubtful that you have heard end about “omega-3 fatty acids.” In fact, you’ll be hearing more and more about this long-chain fatty acid and how important it is to your health, and how American diets should be increased in this nutrient. Isn’t FAT a Four-Letter Word?”
No! Fat is not a bad word! It’s understandable that people have come to believe that all fats are bad for them. For over two decades, dietary guidance has emphasized importance of choosing a diet low in fat, saturated fat, and cholesterol. However, this is wrongly interpreted by consumers to mean that all fat is bad and should be eliminated from diet. In fact, omega-3 fatty acids (and omega-6 fatty acids) are building blocks of every living cell in human body, and are absolutely essential for normal health and development. Since human body is unable to synthesize omega-3 and omega-6 fatty acids, and must obtain them through diet, they are called “Essential Fatty Acids (EFA’s).” Dietary Fats 101: To have a clearer picture in understanding classification of omega-3 fatty acids, let’s review three major categories of dietary fats:
Saturated Fats Monounsaturated Fats Polyunsaturated Fats
As you probably are already aware, these three major categories have various effects on blood cholesterol.
Saturated fats, in general, are shown to elevate LDL-cholesterol (the “bad” cholesterol), type of cholesterol considered to be a major risk factor for heart disease. In contrast, diets higher in monounsaturated and polyunsaturated fats are known to decrease “bad” LDL-cholesterol, without lowering “good” HDL-cholesterol. In addition, when monounsaturated fats are consumed in greater amounts, studies indicate these individuals have lower cholesterol levels.
Within “Polyunsaturated Fats” exists two subclasess of fatty acids (the EFA’s):
Omega-3 Fatty Acids Omega-6 Fatty Acids
Don’t We Already Get Too Much Fat in Diet?
It would appear from our nation’s obesity epidemic that we must be getting too much fat in diet. And, indeed, that is case. However, obesity is not just caused from excess fat, but from a multitude of problems, including excess calories (from all macronutrients, not necessarily just from fat), as well as from inactivity.
No matter what type of fat one consumes, each type has same amount of calories and when eaten excessively without balancing with activity, will contribute to weight gain. However, in addition to being concerned about getting too much fat in diet, one needs to be concerned about ratio of omega-6 fatty acids to omega-3 fatty acids in diet. Beyond Basics: Omega-3 Fatty Acids
The principle omega-3 fatty acid is alpha linolenic acid (ALA). A healthy person will convert ALA into), and then into docosahexaenoic acid (DHA). In other words, ALA is precursor to EPA and DHA, which are omega-3 fatty acids that have significant benefits (see specific foods below).
So, even if we get adequate ALA in our diets from plant sources, such as flax, walnuts, soy, and canola oil, body must still convert it to important EPA and DHA. EPA and DHA, however, are found primarily in fish and fish oils, and when these foods are consumed, body does not have to convert them. The important omega-3 fatty acids, then, for health are:
ALA EPA DHA
Omega-6 Fatty Acids
Linoleic acid is principal omega-6 fatty acid, and it is abundant in most cooking oils, including sunflower, safflower, soybean, and corn oil and processed foods. A healthy person will convert linoleic acid into gamma linolenic acid (GLA), which is then synthesized with EPA from omega-3 fatty acid group, into eicosanoids. Eicosanoids are hormone-like compounds that aid in many body functions, and promote heart health by preventing blood platelets from clotting and sticking to artery walls---effects that are similar to those observed with aspirin. Decreased clotting helps reduce chances of blockages in an artery and thereby decreases risk for heart attack or stroke. Eicosanoids also play a role in reduction of inflammation, significant in heart disease, as well as other diseases like arthritis, lupus, asthma, diabetes.
However, in addition to GLA that is produced from linoleic acid, GLA is also further metabolized to arachidonic acid, which has been shown to have properties of increased inflammation and increased clotting, thereby having potentially negative effects on health. These potentially negative effects, however, are minimized, if omega-6 fatty acids are in proper amounts.
When amounts of linoleic acid (omega-6 fatty acid) are too high, conversion of ALA (omega-3 fatty acids) to EPA (the biologically active form of omega-3 fatty acids), is reduced, and more of GLA is used to make more harmful arachondonic acid, than is used to make more beneficial EPA. As complicated as this sounds, this is a very simplified explanation of process.
To overcome potential negative effects of arachidonic acid, supplementation with GLA-rich foods such as borage oil, black currant seed oil, or evening primrose oil, has become popular. However, this is very controversial, with no scientific evidence to support it, and could be harmful, since GLA is eventually converted to arachidonic acid, thereby, defeating purpose. Therefore, extreme caution should be used with these products.
How Much of Fatty Acids do We Need: Why are our diets too high in omega-6 fatty acids and too low in omega 3-fatty acids?
Human beings evolved consuming a diet that was much lower in saturated fatty acids than is today’s diet. Furthermore, diet contained small and roughly equal amounts of omega-6 and omega-3 fatty acid (ratio of 1-2:1) and much lower amounts of trans fatty acids than does today’s diet. Contrast this to modern American diet in which ratio of omega-6 to omega-3 fatty acids is greater than 10:1, partially due to indiscriminate recommendation to substitute omega-6 fatty acids to lower serum cholesterol concentrations.
