Hydrogenation changes liquid oil to solid. This is done by adding hydrogen. This process is done to make stick margarines in sticks and spreads. That's why margarines in stick form have a lot of trans fats. Rule of thumb: Softer is better. Use healthier canola oil or olive oil for cooking when possible. Look for processed foods that have no partially hydrogenated oils. Choose a margarine that lists liquid vegetable oil as the first ingredient. It should have no more than 2 grams of saturated fat per serving.

Trans fats are in foods made with partially hydrogenated margarine and vegetable shortening. These include pastries and fried foods. Some meat and dairy products have small amounts, too.

The best daily intake is none at all. Trans fats have no health benefits. You should eat a little as possible. Nutrition labels are required by the FDA to state if the food has more than 0.5 grams of trans fats per serving.

Although saturated fats can lead to heart attacks, trans fats are worse. They lower the level of HDL ("good") cholesterol in your body. And they raise the level of LDL ("bad") cholesterol. The Academy of Nutrition and Dietetics advises using margarines that have no trans fat.

Food labels must list the amount of trans fat per serving. They also must list the amount of saturated fat and cholesterol. Keep in mind that a food label can read "0 grams" of trans fat if each serving has less than 0.5 grams. Some foods have partially hydrogenated fats in them, but the small amount per serving means the label can say they have none.

The FDA has taken steps to remove trans fats in processed foods. It now requires that food makers not add partially hydrogenated oils to foods.