A Primer on Fats & Omega-3

You might be surprised to learn that fat plays an important role in keeping our bodies healthy. In fact, you can't live without fat! Fat provides energy, or calories, to help your body function properly. Certain fats are considered to be essential for proper growth, development and functioning of your body. Fat also helps you absorb fat-soluble vitamins like A, D, E, K and carotenoids, serves as a building block for cell membranes, and plays a role in many different essential biological functions in the body1.

While some fat is needed in a healthy diet, both the amount and type of fat you eat matters. According to the latest Dietary Guidelines for Americans, the total amount of fat recommended for adults is between 20 and 35 percent of your daily calorie intake1. The term "total fat" encompasses four different categories: saturated fat, trans fat, polyunsaturated fat, and monounsaturated fat.

Of the total amount of fat that you eat, the majority should come from polyunsaturated and monounsaturated food sources, such as fish, nuts, and vegetable oils1. Less than 10 percent of your calories should come from saturated fat, and trans fat intake should be as low as possible.

Saturated Fat

Saturated fat is found mainly in animal foods like meat, poultry skin, whole milk and whole milk products (such as cheese) and butter. Saturated fat is also in tropical oils, such as coconut, palm and palm kernel oils.

Including too much saturated fat in your diet is a concern, because it may increase "bad" LDL cholesterol levels in the blood. High LDL cholesterol is a recognized risk factor for heart disease.

The Dietary Guidelines for Americans recommend that less than 10 percent of your daily calories come from saturated fat1. So if you eat 2,000 calories a day, your saturated fat intake should be no more than 20 grams (about 23 of an ounce). If you have high LDL cholesterol levels, you should limit saturated fat to no more than seven percent of calories - about 15 grams in a 2,000 calorie/day diet.

Trans Fat

Trans fats are made during a process called "hydrogenation." Hydrogen molecules are added to liquid vegetable oil to help make them more solid and stable at room temperature. Hydrogenating fat helps increase the shelf life and improves the taste and texture of foods containing these fats.

You may find trans fat in some brands of vegetable shortening, margarine, crackers, cookies, snack foods, and commercially fried foods. Like saturated fat, trans fat is a concern because it raises "bad" (LDL) cholesterol levels, which may increase the risk for heart disease. Additionally, however, research suggests that trans fat may also decrease "good" (HDL) cholesterol levels.

The Dietary Guidelines for Americans recommend keeping trans fat intake as low as possible in your diet1.

Monounsaturated Fats (MUFA)

The American Heart Association calls monounsaturated fat one of the "better fats" because when eaten in moderation and used to replace saturated fats or trans fats in the diet, they may help lower "bad" LDL cholesterol levels in your blood, which may reduce your risk for heart disease and stroke2,3.

Foods high in monounsaturated fats include certain vegetable oils, such as olive, sesame, canola, peanut, and sunflower oils, as well as foods like avocados, peanut butter, nuts and seeds2,3.

The Dietary Guidelines for Americans recommend that the majority of your total fat intake come from foods containing monounsaturated and polyunsaturated fats.

Polyunsaturated Fats (PUFA)

The American Heart Association calls polyunsaturated fat one of the "better fats" because when eaten in moderation and used to replace saturated fats or trans fats in the diet, they may help reduce the risk for heart disease3.

Corn, soybean, sunflower, safflower and sesame oils are high in polyunsaturated fats. Fish, flaxseed and nuts are also rich in polyunsaturated fats3.

The Dietary Guidelines for Americans recommend that the majority of your total fat intake come from foods containing polyunsaturated and monounsaturated fats.

Within the polyunsaturated fats family are two types of fat that are important for good health: omega-6 fatty acids and omega-3 fatty acids. Both of these are essential fats that your body needs, but cannot produce on its own, so you have to get them through the foods you eat. Essential fats play a crucial role in brain function and in the normal growth and development of your body.

Omega-6s

The primary omega-6 fatty acid in the U.S. diet is linoleic acid (LA). Consuming adequate amounts of linoleic acid is essential for life and health. Omega-6s have also been shown to help reduce "bad" LDL cholesterol especially when replacing saturated fat as part of a healthy diet. Food sources high in omega-6 PUFAs include corn, soybean, sunflower, safflower and sesame oils.

Omega-3s (EPA, DHA and ALA)

Omega-3 fatty acids are polyunsaturated fatty acids that include EPA (eicosapentaenoic acid), DHA (docosahexaenoic acid) and ALA (alpha-linolenic acid).

EPA and DHA Omega-3

EPA and DHA are found in fish, particularly cold-water, fatty types of fish, such as salmon, sardines, herring, tuna, and lake trout. Research suggests that EPA and DHA may benefit heart health in the following ways4:

  • Decrease the risk of heart arrhythmias (which can lead to sudden cardiac death)
  • Decrease blood triglyceride levels
  • Slow the rate of harmful plaque from forming in your arteries
  • Slightly lower blood pressure

The 2005 Dietary Guidelines for Americans1, as well as the American Heart Association5 recommend eating at least two servings of fish each week, particularly fatty fish varieties rich in EPA and DHA, to improve heart health.

Additionally, the Food and Drug Administration (FDA) has a qualified health claim supporting the heart health benefits of including up to 3 grams (3000 mg) per day of omega-3 EPA and DHA in the diet6. The claim states, "Supportive but not conclusive research shows that consumption of EPA and DHA omega-3 fatty acids may reduce the risk of coronary heart disease. One serving of [name of food] provides [x] grams of EPA and DHA omega-3 fatty acids." [See nutrition information for total fat, saturated fat and cholesterol content.]

EPA and DHA Content of Select Fish

Fish EPA (g) (mg) DHA (g) (mg)
Herring, Atlantic .77/770 .94/940
Salmon, Atlantic, farmed .59/590 1.24/1240
Salmon, Coho, wild .34/340 .56/560
Tuna, Bluefin .31/310 .97/970
Trout, mixed species .22/220 .58/580
Shrimp .15/150 .12/120
Tuna, canned in water, light, solids only .04/40 .19/190
Cod, Atlantic 0/0 .13/130

ALA Omega-3

Another type of omega-3 fatty acid is alpha-linolenic acid or ALA. ALA is necessary for normal growth and development and is an essential fatty acid, meaning that you must get ALA from the foods you eat because your body cannot make it. ALA is found in plants, not fish. Significant sources of ALA include canola and soybean oils, flaxseed, walnuts, pumpkin seeds, and leafy greens such as kale4.

The Institute of Medicine has set an Adequate Intake level for ALA of 1.6 grams (1600 mg) per day for men and 1.1 grams (1100 mg) per day for women (7). The American Heart Association states that a total intake of 1.5-3 grams of ALA (1500 to 3000 mg) per day appears to be beneficial5.

ALA content of select foods

Food ALA (g) (mg)
Walnuts, English (1ounce) 2.57/2570
Flaxseeds, ground (1Tbsp) 1.60/1600
Canola oil (1 Tbsp) 1.23/1230
Soybean oil (1 Tbsp) 0.92/920
Tofu, firm (12 cup) 0.73/730
Kale, raw, chopped (1cup) 0.12/120
Olive oil (1 Tbsp) 0.10/100
Pumpkin seeds (1 ounce) 0.05/50

In order for your body to use ALA it must convert it into EPA and DHA. Unfortunately, the conversion rate of ALA to EPA and then from EPA to DHA is very low (8). Therefore, to receive the potential heart health benefits of EPA and DHA, nutritionists recommend including at least two servings (~8 ounces) of fish per week in your diet.

Overall Recommendations

Most people consume too much saturated and trans fats in their diets, compared to the "better" unsaturated fats. In terms of fat intake, the best dietary advice is to keep the overall amount you eat moderate, between 20 and 35 percent of your total calories.

To benefit heart health, choose foods containing polyunsaturated and monounsaturated fats over those high in saturated fat and trans fat, whenever possible. Keep saturated fat intake to less than 10 percent of the calories you eat, and trans fat as low as possible in your diet.

To increase EPA and DHA omega-3 intake, eat at least two servings (~8 ounces) of fatty fish per week. To get the essential fatty acids ALA omega-3 and LA omega-6, include in your diet nuts, seeds and vegetable oils such as soybean, sunflower and corn.

Sources:

  1. Dietary Guidelines for Americans, 2005. http://www.health.gov/dietaryguidelines/dga2005/document/html/chapter6.htm
  2. American Heart Association. Monounsaturated fats. http://www.americanheart.org/presenter.jhtml?identifier=3045795
  3. American Heart Association. Consumer FAQ - "Better" Fats (Monounsaturated and Polyunsaturated Fats). http://www.americanheart.org/presenter.jhtml?identifier=3046644#def_omega6
  4. Gebauer SK, Psota TL, Harris WS, Kris-Etherton PK n-3 Fatty acid dietary recommendations and food sources to achieve essentiality and cardiovascular benefits. Am J Clin Nutr 83(6): S1526-1535S. http://www.ajcn.org/cgi/content/full/83/6/S1526
  5. American Heart Association. Fish and omega-3 fatty acids. http://www.americanheart.org/presenter.jhtml?identifier=4632
  6. FDA. Qualified Health Claim for Omega-3 Fatty Acids, Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA). http://www.cfsan.fda.gov/~dms/labo3qa.html
  7. Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein and Amino Acids. The National Academies Press, 2005.
  8. Position of the American Dietetic Association and Dietitians of Canada: Dietary Fatty Acids. J Am Diet Assoc. 2007; 107: 1599-1611.

* Contains 960 mg of ALA per serving, which is 60% of the 1.6g daily value for ALA. ALA is a fatty acid found in walnuts. For information about ALA's relationship to other Omega-3 fatty acids
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