Understanding Fats

Sorting out the fats

Eating low fat food doesn’t mean we should give up fat entirely, but we do need to educate ourselves about which fats should ideally be avoided and which ones are more heart-healthy. Let’s be clear: we need fat in our diet. As the most concentrated source of calories (nine calories per gram of fat compared with four calories per gram for protein and carbohydrates), it helps supply energy. Fat provides linoleic acid, an essential fatty acid for growth, healthy skin and metabolism. It also helps absorb fat-soluble vitamins (A,D,E and K). And, face it, fat adds flavor and is satisfying, making us feel fuller, keeping hunger at bay.

Although all fats have the same amount of calories, some are more harmful than others: saturated fats and trans fats in particular.

Saturated fats

These fats are derived from animal products such as meat, dairy and eggs. But they are also found in some plant-based sources such as coconut, palm and palm kernel oils. These fats are solid at room temperature. Saturated fats directly raise total and LDL (bad) cholesterol levels. Conventional advice says to Avoid them as much as possible. More recently, some have questioned this, as there are different kinds of saturated fats, some of which have at least a neutral effect on cholesterol.

Trans Fats or Hydrogenated Fats

Trans fats are actually unsaturated fats, but they can raise total and LDL (bad) cholesterol levels while also lowering HDL (good) cholesterol levels. Trans fats are used to extend the shelf life of processed foods, typically cookies, cakes, fries and donuts. Any item that contains “hydrogenated oil” or “partially hydrogenated oil” likely contains trans fats. Hydrogenation is the chemical process that changes liquid oils into solid fats. The tide is turning against trans fats. Since January 2006, all food manufacturers are required to list trans fat content on food labels.

Unsaturated fats

Monounsaturated fats and polyunsaturated fats are two types of unsaturated fatty acids. They are derived from vegetables and plants.

• Monounsaturated fats are liquid at room temperature but begin to solidify at cold temperatures. This type of fat is preferable to other types of fat and can be found in olives, olive oil, nuts, peanut oil, canola oil and avocados. Some studies have shown that these kinds of fats can actually lower LDL (bad) cholesterol and maintain HDL (good) cholesterol.
• Polyunsaturated fats are also liquid at room temperature. These are found in safflower, sesame, corn, cottonseed and soybean oils. This type of fat has also been shown to reduce levels of LDL cholesterol, but too much can also lower your HDL cholesterol.

Omega-3 fatty acids

These include an “essential” fatty acid, which means it's critical for our health but cannot be manufactured by our bodies. Good sources of omega-3 fatty acids include cold-water fish, flax seed, soy, and walnuts. These fatty acids may reduce the risk of coronary heart disease and also boost our immune systems.

By Fiona Haynes, About.com Guide