Saturated animal fats have always had a bad reputation for increasing the risk of heart disease. Researchers, however, have recently identified an even more insidious enemy of the cardiac system -- trans fatty acid -- which is used to make margarines (previously touted as a healthier alternative to butter). But why is trans fat so bad?

What is trans fat?

Trans fat is a type of fat which is formed when food manufacturers change liquid oils to more stable semisolid fats, for example, when they make shortening or hard margarine.

Trans fat is bad news for heart, because it has two unhealthy effects on our cholesterol levels: It not only raises LDL cholesterol (the "bad" kind of cholesterol), but also reduces HDL cholesterol (the "good" cholesterol) levels in the body. In fact, it is believed to be even worse for our heart than saturated fat.

How much trans fat should we consume?

Currently, there isn't a recommended daily limit for trans fat intake, but you should consume as little as possible.

What can I do to reduce trans fat in my diet?

For starters, limit your consumption of margarines, commercially-baked and deep-fried foods and products including pastries, cakes, crackers, cookies and biscuits, since these are the main sources of trans fat in our diet.

When shopping, make it a habit to read and compare food labels for the content of trans fats in food products, and choose the brand with the lowest amount of trans fatty acid. Check the ingredient list and watch out for words such as vegetable shortening and hydrogenated or partially hydrogenated oils -- these mean the food contains trans fat. Better yet, choose fresh produce such as fruits and vegetables over processed foods.