Recent studies have suggested that trans fatty acids have a deleterious effect on cholesterol levels and the risk of heart disease, and point out that we're eating far more of these evil fats than we should, and far more than we used to. (Click here for a quick review of
cholesterol.)
What are trans fatty acids, and where do they come from?
We're used to hearing about saturated and unsaturated fatty acids. Saturated fatty acids - which come from animal fats (meat, lard, dairy products) as well as tropical oils such as coconut and palm oils - raise the levels of LDL cholesterol. Unsaturated fats - which come from vegetable oils - in general, do not increase cholesterol levels, and may reduce them.
Because saturated fatty acids were found to be bad for you a couple decades ago, the food industry wanted to switch to using unsaturated fatty acids. Unfortunately, unsaturated fatty acids become rancid relatively quickly. To combat the instability of unsaturated fatty acids, manufacturers began to "hydrogenate" them, a process that makes them more stable. The result was a more solid and longer lasting form of vegetable oil, called "partially hydrogenated" oil.
Unfortunately, when unsaturated vegetable fats are subjected to the process of hydrogenation, a new type of fatty acid is formed. This new type of fatty acid is called trans fatty acid. So when manufacturers began substituting partially hydrogenated vegetable oils for saturated fats in processed foods, they began adding - for the first time - relatively large amounts of trans fatty acids to the typical diet.
So what's the problem with trans fatty acids?
Trans fatty acids turn out to increase total cholesterol levels and LDL cholesterol levels, and to reduce HDL cholesterol levels. In other words, trans fatty acids are detrimental to cardiac health.
Which is worse - saturated fatty acids or trans unsaturated fatty acids?
Both saturated fats and trans fatty acids are bad for you. Saturated fats are almost always found in foods that also contain cholesterol, so saturated fats offer a "one-two" punch to heart health. On the other hand, trans fatty acids not only increase LDL cholesterol, they also decrease HDL cholesterol. So while nobody can say yet definitively which is worse, it does appear that both are bad.
What is the FDA doing about trans fatty acids?
The U.S. Food and Drug Administration now recognizes the health risk of trans fatty acids, and has mandated new food labeling standards that require the trans fatty acid content to be included on the label. The FDA has not indicated a "safe level" of trans fatty acids, as their scientific panel decided that any amountof trans fatty acids is bad. The new labeling requires food companies to list the amount of trans fatty acids (as well as saturated fats) in all processed foods.
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