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Trans-Fatty Acids - What You Need to Know

Trans-fatty acids have been getting a lot of attention in the media lately, yet not everyone knows what they are, why they should be avoided, and how to avoid them. Here is the low-down:

What are trans-fatty acids?

First, naturally-occurring fats come in 2 forms: saturated and unsaturated. Saturated fats are typically found in animal products, such as meats and dairy products, including milk and butter. Unsaturated fats are found in vegetable sources, and include olive, corn, and canola oil. Saturated fats are solid at room temperature, whereas unsaturated fats are liquid at room temperature.

Saturated fats in the diet are associated with health risks such as high cholesterol, high levels of LDL (bad cholesterol), cardiovascular disease, arteriosclerosis, and obesity. Unsaturated fats, on the other hand, can lower your "bad" cholesterol and possibly raise your "good" HDL cholesterol. Thus, health practitioners advise that people get most of their fat from unsaturated rather than saturated sources.

This is where the confusion sets in. Many commercially-prepared food products are made from hydrogenated or partially-hydrogenated vegetable oils. Thus, they appear to be healthy - they are low in saturated fat, and they contain vegetable oils, a source of unsaturated fat. These products should be healthy, right? Wrong - during the process of hydrogenation, the once heart-friendly vegetable oils are transformed into trans-fatty acids, a type of fat that is now believed to be even worse for your health than saturated fat.

Why should trans-fatty acids be avoided?

Trans-fatty acids have some of the same properties as a saturated fat, and can raise your "bad" LDL cholesterol while also lowering your "good" HDL cholesterol. In fact, the effect of trans fatty acids on your HDL/LDL ratio is nearly double that of saturated fats. In addition, trans fats can raise your triglyceride levels more than saturated fat can. Epidemiological studies have also shown that trans fats can cause an increased risk of coronary heart disease.

Why do food companies use trans-fatty acids?

Unsaturated fats have a shorter shelf-life than saturated fats because they are more easily oxidized - that is, oxygen molecules from the air can attack the fatty acid chain. When this happens, the fat develops an off-flavor and may change color - you may notice this when you use an oil that has been sitting around a while. This is also known as rancidity. Therefore, food companies hydrogenate unsaturated fats, giving them the properties of a saturated fat, namely, a longer shelf-life, and an increased resistance to oxygen molecules that can destroy the fat.

Sources of trans-fats:

The easiest way to determine whether a product contains trans fats is to look at the ingredient label. If it contains hydrogenated or partially-hydrogenated vegetable oil, the product contains trans fats. The closer the ingredient is to the beginning of the ingredient list, the more of that ingredient is contained in the product. Thus, if the trans fat is listed toward the beginning of the list, then it is a major component of that product.

For example, here is a sample ingredient list from a box of Cheese NipsT:

Ingredients: ENRICHED FLOUR (WHEAT FLOUR, NIACIN, REDUCED IRON, THIAMINE MONONITRATE [VITAMIN B1], RIBOFLAVIN [VITAMIN B2], FOLIC ACID), PARTIALLY HYDROGENATED SOYBEAN OIL , CHEDDAR CHEESE (MADE FROM CULTURED MILK, SALT, ENZYMES, AND ANNATTO EXTRACT), SALT, AUTOLYZED YEAST EXTRACT, LEAVENING (BAKING SODA, YEAST), MONOSODIUM GLUTAMATE (FLAVOR ENHANCER), ANNATTO EXTRACT (VEGETABLE COLOR), PAPRIKA, SODIUM CASEINATE (A MILK PROTEIN), LACTIC ACID AND ACETIC ACIDS, SPICES, MALTED BARLEY FLOUR.

In the above example, partially hydrogenated soybean oil is listed toward the top of the list. While the trans fat content is not currently listed on the box, the manufacturer states that this product contains 2g of trans fat per 30g serving (www.kraftfoods.com).

Products that are typically high in trans fats include:

• Stick margarine, and to a lesser extent, tub margarine
• Solid food shortening, such as Crisco ®
• Baked goods, such as cookies, crackers, breads, muffins, doughnuts, cakes (this does not include home-baked goods, unless a vegetable shortening such as Crisco ® was used)
• Fast food, including French fries
• Peanut butter (except many natural peanut butters (ie: Laura Scudders)
• Dairy-free whipped topping, such as Cool-Whip ®

Trans-fats on Nutrition Facts labels:

Beginning in January, 2006, the FDA will require Nutrition Facts labels to include trans-fats. Trans-fats will be listed under Saturated fat in the Total fat category. Here is an example of what the new Nutrition Facts label would look like:

What should I do?

• Until January 2006, look carefully at ingredient labels before buying a product that you suspect contains trans fats.
• Some products now offer non-trans fat versions: there is now a trans-fat free peanut butter on the market, as well as a trans fat-free bread.
• Look for products that advertise themselves as trans fat free
• Use liquid vegetable oils such as olive oil for cooking, instead of margarine.
• If you must use margarine, use a soft margarine - these usually come in tubs. A void using stick margarines.
• Do not be afraid to ask your server if the food you are eating contains trans fats.

 

References:

Ascherio A, Stampfer MJ, and Willett WC. Trans Fatty Acids and Coronary Heart Disease, Harvard School of Public Health, [http://www.hsph.harvard.edu/reviews/transfats.html].Retrieved May 17, 2004.

Insel, P., Turner, R.E., and Ross. D. (2002). Nutrition . Boston : Jones and Bartlett Publishers.