Dietary Fats

For all its bad press, dietary fat is not onlyuseful, it's essential for good health. It's one of the three nutrientsthat supply energy (along with carbs and protein), providing essentialfatty acids. Dietary fat is a concentrated energy source in foods. Itcarries the fat-soluble vitamins A, D, E, and K, assisting in theirabsorption. It provides the raw material for making needed products inthe body. Fat contributes to the taste and smell of foods and makesfoods tender, such as certain cuts of beef. It also stimulates theappetite and contributes to feelings of fullness, staying longer in thedigestive system.

Saturated vs. Unsaturated Fats

Dietaryfat can be classified as either saturated or unsaturated. The moreunsaturated the fat, the more liquid it is at room temperature. Let'sstart first with saturated fats. They are called saturated because theycarry all the hydrogen atoms they can hold and they come mainly fromanimal sources. Saturated fats are considered unhealthy because theyraise blood cholesterol and increase the risk of heart disease, theyshould be limited to less than 7% of total calories according to theAmerican Heart Association. They are found in three vegetable oils:coconut, palm, and palm kernel and are the primary fats in butter,whole milk, whole milk cheese, and meats.

Unsaturated fats,referred to as unsaturated because they do not hold all the hydrogenatoms they can carry, include monounsaturated if missing one pair ofhydrogen atoms and polyunsaturated if missing two pairs or more ofhydrogen atoms. They come primarily from plants and fish and areconsidered heart-healthy fats because they don't raise bloodcholesterol and may, in fact, lower LDL (bad cholesterol). Unsaturatedfats should be most of the 20 - 35% of total calories allowed for fats,according to the American Heart Association. They are found in oilssuch as canola, olive, peanut, safflower, flaxseed, corn, and soybeanas well as in nuts, flaxseed, soy beans, avocado, salmon, and otherfatty fish. While these fats are good for us, it's important to keep inmind that portion control is required because all fats are higher incalories than the other two nutrients that provide energy (9 caloriesper gram for fats vs. 4 for carbohydrates and protein each). To keep these two fats straight, remember that saturated fats saturate your arteries - not a good thing!

Understanding Trans Fats

Transfats are formed when hydrogen is added to liquid vegetable oil tocreate a more solid form by a process called "hydrogenation." Transfats are highest in stick margarines, baked goods such as cookies,commercially fried foods like French fries, and crackers. Foodmanufacturers have replaced saturated fats with partially hydrogenatedoils to make margarines and spreads solid at room temperature and toextend the shelf life of foods. Trans fats delay rancidity while makingfoods moist, flaky, and flavorful.

Like saturated fats, transfats raise the risk of heart disease by increasing "bad" low-densitylipoprotein (LDL) cholesterol levels. It is believed that trans fatsalso lower "good" high-density lipoprotein (HDL) cholesterol, whichsaturated fats do not. This makes trans fats at least as bad assaturated fats and possibly worse.

In addition, trans fats havenegative health effects beyond heart disease, having been linked toAlzheimer's disease, macular degeneration, and gallstone disease andinflammation. Although trans fats are found in animal products likedairy foods and meat, this naturally occurring form is different fromthose that result from hydrogenation and do not cause the same negativehealth effects.

As of July 2006, the American Heart Associationadvises keeping saturated fats consumed to less than 7% of calories perday and trans fat consumption to less than 1% per day. This meanssomeone eating 2,000 calories would be able to consume up to 16 gramsof saturated fat and 2 grams of trans fat. The Institute of Medicinerecommends keeping trans fat consumption "as low as possible" while the2005 Dietary Guidelines recommend a trans fat intake of less that 1% ofcalories, 2 grams for an 1,800 calorie diet. This is the amounttypically occurring naturally from dairy and meat products.

Whilefood manufacturers are required to list trans fats on food labels, thiscan be misleading. Foods that have less than 0.5 grams of trans fat perserving may be listed as having "0" trans fats (and can be labeled as"trans free"). However, such a food could actually possess as much as0.4 grams of trans fat per serving, which can add up if multipleservings are consumed. To minimize the chance of consuming hiddentrans fats, check the ingredient list for partially hydrogenated oils.If any are listed, some trans fats are present, so don't eat more thanone serving, if you have any at all.