The Truth about Fats and Oils and Health

The fusion of flavors in stir-fried vegetables. The creaminess of ice cream. The smooth freshness of sliced avocado. The flake in a croissant. These are the benefits of fats and oils from the consumer’s perspective. Enjoying these food experiences is often seen as a guilty pleasure, but there is actually a role for fat in the diet.

Indeed, for every gram of fat, we consume more than twice the calories than we get from an equal weight of carbohydrate or protein (1 g fat yields 9 calories; 1 g protein yields 4 calories; 1 g carbohydrate yields 4 calories). Since food is made up of varying proportions of fat, protein, and carbohydrate, reducing fat in the diet was for many years presumed to be the most efficient way to cut calories without eating less. However, consumers, health professionals, and scientists have learned that aiming to eliminate fat from the diet as a means of weight loss may not be the best solution without attention to overall caloric intake.

First of all, research comparing the effects of diets with equal amounts of calories but varying proportions of fat, carbohydrate, and protein has revealed that there are no differences in weight loss. Calorie reduction matters most, meaning that replacing fats with carbohydrates or proteins may not improve weight loss efforts if calories are held constant, or if the carbohydrate or protein substitution actually increases calories.

Second, fat is satisfying—providing a desired mouth-feel and feeling of fullness. People who do not feel satiated by the food they’ve eaten, either because the flavor was missing or the food was not filling, may be more likely to continue eating in search of those sensations, likely offsetting any caloric deficit created by removing fats from foods.

Beyond the enjoyment and satisfaction that fat adds to foods, it is a critical player in human health. The essential functions of fat in the body are not breaking news, but at times they have been forgotten. Fats—and components of or products of metabolism of fats—are found in the wall of each cell in the human body, and are particularly critical components of the brain and nervous tissue. Fats are used to make hormones that affect such bodily functions as blood pressure, blood clotting, immune function, and smooth muscle contraction. Fat-soluble nutrients, such as vitamins A, D, E, and K and the carotenoids, rely on fat for proper absorption. Protective insulation is provided by subcutaneous fat, and protective cushioning by the thin layer of fat that covers internal organs. It is no surprise, then, that 55 percent of the calories in breast milk come from fats, critical for the developing human body.

Consistent with the 2005 Dietary Guidelines for Americans, the 2010 Dietary Guidelines Advisory Committee concluded that most dietary fats should be polyunsaturated and monounsaturated (i.e., fats that are liquid at room temperature), rather than saturated or trans (i.e., solid at room temperature). This conclusion signals an emerging consensus around the particular benefits of certain types of fats, rather than the amount of total fat consumed within calorie needs. While it has long been known that linoleic acid (LA) and alpha-linolenic acid (ALA) are essential fatty acids which must be obtained from the diet, the story is richer than once thought. For example, while very long chain omega-3 polyunsaturated fats (docosahexaenoic acid (DHA)and eicosapentaenoic acid (EPA), (found in fatty fish and certain algae) are the most protective against sudden cardiac death, ALA, the precursor to EPA and DHA that is found in the oil portion of flaxseed, soybeans, walnuts, and other plants, may be heart-protective. While saturated fat in excess increases heart disease risk, stearic acid is one type of saturated fat that has no effect on blood cholesterol levels when substituted for saturated or trans fats. Finally, moderate dietary cholesterol intake is recognized as having little effect on heart disease risk in healthy individuals (although risk may increase in people with diabetes).   Plant stanols and sterols are thought to play a role in the reduction of heart disease risk among those who consume a plant-based diet.

Have the reins been loosened on fat so much that “splurge” is the new health trend? No, calories from all sources count. As scientific evidence regarding the benefits and risks of particular fatty acids continues to evolve, the current consensus is that moderation applies to dietary fat as much as other nutrient and lifestyle choices. Importantly, fat is not to be feared; it is a critical component of a healthful diet. The Institute of Medicine notes the acceptable range for fat consumption among adults is 20 to 35 percent of total calories.  For an adult consuming a 2,000-calorie diet, the range would be between 45 and 78 grams of fat per day.

Balancing Fats for Health

Unsaturated Fats:  When consumed regularly, as part of a sensible, balanced diet, unsaturated fats may help lower LDL cholesterol (the kind you want less of) and raise HDL cholesterol (the “good” kind).  Unsaturated fat is liquid at room temperature.  There are two types of unsaturated fat: monounsaturated fat and polyunsaturated fat—and these are the fats that should replace saturated fat in your diet whenever possible. The International Food Information Council Foundation’s 2010 Food and Health Survey found that less than half of consumers said they were trying to eat more unsaturated fats; evidence that many people don’t understand the role or benefits of these dietary fats.

Sources include avocado, fish (albacore tuna, herring, lake trout, mackerel, salmon, and sardines), flax, olives, peanuts, tree nuts, seeds, and canola, corn, peanut, safflower, soybean, and sunflower seed oils. 

Saturated Fats:  These fats are found in meats, fish, poultry, dairy products, most chips, and packaged cookies, cakes and pastries. Saturated fats should be consumed less often since they can raise your LDL cholesterol.

Sources include fatty cuts of meat, poultry skin, stick butter or margarine, full-fat dairy foods (such as regular cheese), tropical oils (coconut oil, palm oil, palm kernel oil, cocoa butter), vegetable shortening, partially hydrogenated vegetable oils, tallow, lard, and some candies and desserts.

Trans-Fatty Acids:  Trans fats are made when liquid oil has hydrogen added.  The process makes a more solid fat that is more versatile than liquid oils, aids in preserving the freshness of products, and, in commercially prepared foods, provides a taste and texture similar to regular fat.  Despite these desirable characteristics, research has found trans fats are not heart-healthy fats, so in the past few years many food manufacturers have successfully removed or reduced trans fats in their food products.

Sources of trans fats include some fried foods, stick margarine, many packaged cookies, cakes, pastries and snack food.

Dietary Fats Research on the Cutting Edge

  • Omega-3 fatty acids were once close to being dismissed as ineffective for heart disease risk reduction because of a lack of full understanding of their effects on blood cholesterol levels, but increasingly, scientific research demonstrates protection for the heart and brain.
  • Replacing saturated fat with monounsaturated or polyunsaturated fat may improve glycemic and inflammatory markers in individuals with type 2 diabetes.
  • Stearic acid is one type of saturated fat that may be blood cholesterol-neutral.
  • Study of the relationships between genetics, health, and lifestyle is progressing rapidly with respect to fats and cardiovascular and other chronic diseases, illuminating options for more effectively targeted prevention and treatment options.