Fat provides many useful and functional properties, yet fat—especially trans fat—remains a controversial subject.
Fat is an essential nutrient that provides energy (nine calories per gram), Vitamin E and two essential fatty acids: linoleic acid (omega-6) and alpha-linolenic acid (omega-3). In addition, fat helps produce hormones and carry the fat-soluble vitamins A, D, E and K.
In cooking, fat adds texture and flavor. In baking, fat tenderizes, moisturizes, holds air and affects shape and color (browning). Fat also conducts heat, lubricates foods, seals in moisture (e.g., basting) and prevents sauces from curdling.
In 2002, the National Academy of Sciences’ Institute of Medicine advised adults to limit fat intake to 20% to 35% of total daily calories with more unsaturated fats and as little saturated fats and “trans fats” (hydrogenated oils) as possible. Understanding the types of fats and their food sources can help you develop more healthful menus, guide customers’ choices and help them address health concerns.
Types of fats: All fats contain about 120 calories and 14 grams of fat per tablespoon. Fats are classified by the predominant type: saturated, monounsaturated or polyunsaturated. Here’s a summary of their possible health benefits and risks:
Saturated fat raises total and “bad” low-density lipoprotein (LDL) cholesterol to increase risk of heart disease and certain cancers (e.g., breast, colon). Saturated fat, usually solid at room temperature, has a greater effect on LDLs than dietary cholesterol (found only in animal foods). The National Institutes of Health (NIH) advises limiting saturated fat to 7% or less of total daily calories. Examples include butter, lard, solid vegetable shortening, meat, whole milk, coconut, palm and palm kernel oils.
Some recent research suggests palm and coconut oils may not raise blood cholesterol as was once believed. But, more research is needed. Melting butter or stick margarine won’t reduce saturated fat. When cooled, these fats become solid again.
Monounsaturated fat (MUFA), when substituted for saturated fat, reduces total and LDL-cholesterol and may boost “good” (high-density lipoprotein (HDL) cholesterol slightly. MUFA may reduce risk of heart disease and stroke and help treat diabetes and hypertension. Examples include olive oil (highest in MUFA), canola oil (lowest in saturated fat), peanut, rice bran, almond and hazelnut oil, avocado, most nuts and tub margarines.
Olive oil, rich in antioxidants like polyphenols, may also reduce risk of rheumatoid arthritis, Alzheimer’s disease and cancer (e.g., breast, colon). The Food and Drug Administration (FDA) recently approved a food label health claim for olive oil stating that two tablespoons a day (in place of a similar amount of saturated fat) may reduce risk of heart disease due to MUFA.
Monounsaturated oils may be healthier for cooking than polyunsaturated oils which are more susceptible to oxidation (cell damage that can lead to cancer or heart disease), especially when heated to high temperatures (e.g., frying) for prolonged time. Reheating frying oil is harmful, too.
Polyunsaturated fat (PUFA), when substituted for saturated fat, lowers total and LDL-cholesterol more than MUFA does. There are two types: omega-6 and omega-3 fats. The latter may boost immunity and help prevent cancer, Alzheimer’s disease, macular degeneration, inflammation (marker for heart disease) and blood clots. Omega-3s may also relieve rheumatoid arthritis and reduce high blood triglycerides and blood pressure.
Excess omega-6 fats compared to the amount of omega-3s may promote heart disease, cancer and inflammation (e.g., arthritis). Omega-6 fats include safflower and sunflower oils (both also available as MUFA), soybean, sesame, corn, cottonseed and grape seed oils, mayonnaise, margarine and salad dressings. Omega-3 fats are found in fatty fish (oils) like salmon, sardines, tuna, swordfish and mackerel, flaxseed, soybeans, walnuts, wheat germ and their oils, and canola oil (MUFA).
Trans-fats: Trans-fats are PUFA that are chemically altered to become harder (more saturated) for stability and longer shelf life. They have higher melting points and thus are more stable for frying. Trans-fats act like saturated fat by raising total and LDL-cholesterol, but also reduce HDLs. Trans-fats may raise risk for heart disease, diabetes, macular degeneration, cancer and Alzheimer’s disease.
Look for trans-fats as “hydrogenated” or “partially hydrogenated” oils on food labels. By January 1, 2006, manufacturers must start listing trans fat content on food labels. Trans-fats are found in some margarines, butter, meat, dairy, peanut butter, popcorn, candy bars, crackers, chips, fried foods and baked goods (e.g., cookies, donuts).
It’s estimated that trans-fats supply only 2%-4% of our daily calories compared to 12% from saturated fats. But, trans-fat intake may be higher and more detrimental to health than saturated fat. So cook and bake with “trans-free” margarines or liquid vegetable oils low in saturated fat (e.g., canola, olive, soybean, corn or safflower).