The Basics on Trans Fatty Acids

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It is now known that trans fatty acids have a deleterious effect on cholesterol levels and cardiac risk. It is important for us to attempt to eliminate food containing trans fatty acids from our diets.

For decades we all have heard 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 judged to be bad for heart health, both public health experts and the food industry were anxious to find ways of eliminating them from processed foods. However, the "good" unsaturated fatty acids become rancid relatively quickly and are unsuitable for products having a long shelf life. 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, or trans fatty acids.

The Problem With Trans Fatty Acids

It turns out that trans fatty acids turn total cholesterol levels and LDL cholesterol levels, and reduce HDL cholesterol levels. They also appear to increase inflammation.

In other words, trans fatty acids are quite detrimental to cardiac health - far more detrimental (it is now generally agreed) than the saturated fat they were designed to replace.

What Is Being Done 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 any "safe level" of trans fatty acids, as their scientific panel decided that any amount of 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.

The goal, clearly, is to eliminate trans fatty acids from processed foods altogether.

Which Foods Contain Trans Fatty Acids?

Fortunately, it is pretty easy to identify foods that contain relatively large amounts of trans fatty acids: margarines (the more solid the margarine, the more the trans fatty acids; stick margarines contain the most, tub margarines contain less, and semi-liquid margarines contain the least;) high-fat baked goods (especially doughnuts, cookies and cakes;) and any product for which the label says "partially hydrogenated vegetable oils."

All of these should be avoided in a heart healthy diet. Furthermore, keep in mind that processed foods, especially baked goods, must include some type of shortening in order to have a reasonable shelf life.

These foods no longer contain saturated fats (long since hounded out of use), and now presumably they contain no (or few) trans fatty acids.

So, what do they contain? The fact is, this is unknown. Presumably they contain some sort of processed vegetable oil that has the structural properties of saturated fats. (Otherwise, they would be of no use as shortening.) How safe these new, unknown products may be is not known.

This is another very good reason to avoid eating processed foods, as much as you possibly can.


Oomen CM, Ocké MC, Feskens EJ, et al. Association between trans fatty acid intake and 10-year risk of coronary heart disease in the Zutphen Elderly Study: a prospective population-based study. Lancet 2001; 357:746.

Mozaffarian D, Katan MB, Ascherio A, et al. Trans fatty acids and cardiovascular disease. N Engl J Med 2006; 354:1601.


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