Recently, New York City banned trans-fats and is giving city restaurants a year to remove trans-fats from the food they serve. Just this week, the restaurant chain Denny’s announced plans to remove trans-fats from the food they serve as early as the first half of 2007.

There seems to be a great deal of press about trans-fats lately, so I thought I might discuss what all the concern is about.Fat is an interesting subject. The common fats that are commonly discussed in nutrition are saturated fats and unsaturated fats. Saturated fats are typically animal fats and are found in meat, chicken, butter, and dairy products. The few plant sources of saturated fat include tropical oils like palm and coconut oils. Saturated fats in our diet tend to increase bad cholesterol

Unsaturated fats are a large group that includes both beneficial fats like the omega-3 polyunsaturated fats which are commonly found in both fish oil and flax seed and also dangerous synthetic fats like trans-fats. Some unsaturated fats like omega-3 polyunsaturated fats are required for proper nutrition; the body cannot create these fats required for proper cell and immune functioning from raw materials and thus must obtain these fats through dietary sources. Other polyunsaturated fats can be found in corn oil, sunflower oil, and soybean oil. Also within the group of unsaturated fats are monounsaturated fats which can be found in canola oil, olive oil, and peanut oil. Likewise, both polyunsaturated and monounsaturated natural fats do not contain any trans-fats.

Trans-fats are unsaturated fats that have hydrogen atoms added to them via a process called hydrogenation. Hydrogenation is done in a factory; hydrogenation is a form of processing that produces a synthetic fat. Most natural polyunsaturated fats are plant-based and oily in consistency. Typically, to make a solid like margarine or shortening, a natural, unsaturated fat like corn oil or soybean oil is hydrogenated, or partially hydrogenated. Solid refers to the state of the fat at room temperature; solid fats can, of course, can be melted with heat. These solid trans-fat products are then commonly used for deep-frying or in helping food items (like cookies, crackers, or cakes) remain moist. The benefit of these hydrogenated trans-fats to restaurants and food producers are that these fats keep longer and can be stable at higher temperatures. Using hydrogenated oils gives products longer shelf times, creates foods moistness without being oily, and allows deep-fryers to operate at higher temperatures for a longer time without having to change the oil.

The reason these hydrogenated fats last longer is due to a particular chemical bond. In chemistry, the bond that arises with hydrogenation is called a “trans” bond. This “trans” refers to the configuration of the fat molecule. Therefore, a hydrogenated oil or fat is usually called a “trans” fat. Trans-fats do occur in nature, but they are not common in most fruits or vegetables. Most of the naturally occurring trans-fats can be found in meat, milk, and dairy products. These natural trans-fats make up only 15 to 20% of the trans-fats in a typical American diet. Also, these natural trans-fats have not been shown to have the harmful properties of the hydrogenated (synthetic) trans-fats. Most of the trans-fats in our diets are synthetic hydrogenated and partially-hydrogenated oils in fried foods or processed food items.

The most important concept when thinking about all the different types of fats is understanding how the body deals with each type of fat and the effect of cholesterol. Remember, LDL is the bad cholesterol that tends to be deposited into blood vessel walls leading to atherosclerosis, clogged arteries, heart attacks, and strokes. HDL is the good cholesterol that actually carries excess cholesterol to the liver for removal from the body. The greatest risk of atherosclerotic heart disease and stroke occurs with high LDL levels and low HDL levels. Here is how each type of fat affects cholesterol levels in the body:

Saturated Fat:
Raises LDL (bad cholesterol) and raises HDL (good cholesterol).
Natural Polyunsaturated Fat:
Lowers LDL, raises HDL
Monounsaturated Fat:
Lowers LDL, raises HDL
Trans Fats (Polyunsaturated fats that have been hydrogenated):
Raises LDL and lowers HDL (Highest Risk Fat)

By lowering HDL and raising LDL, trans-fats are a double whammy for heart disease and stroke risk. So, read the labels on the foods you are eating. Avoid margarine, shortening, and hydrogenated or partially-hydrogenated oils in your diet. And now that you know the lingo, you can avoid being confused, because while soy is a superfood, partially-hydrogenated soybean oil is definitely not. And, be aware, many items and foods that say “no trans fats” still have hydrogenated oils listed on their label. So use your new background in trans-fats to be smart about what you eat.