The Basics on Trans Fatty Acids and the Heart

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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.

What Are Trans Fatty Acids (Trans Fats)?

Natural foods (that is, unprocessed foods) contain two main types of fatty acids - saturated and unsaturated. Saturated fatty acids - which come from animal fats (meat, lard, dairy products) and tropical oils such as coconut and palm oils - can raise your blood levels of LDL cholesterol.

 Unsaturated fatty acids in general do not increase cholesterol levels, and may reduce them.

Trans fatty acids (trans fats) are a third form of fatty acids. While trans fats do occur in tiny amounts in some foods (particularly foods from animals), almost all the trans fats now in our diets come from an industrial process that partially hydrogenates (adds hydrogen to) unsaturated fatty acids from vegetable oils. This means that in our diets, trans fats are almost exclusively found in the processed foods we eat.

The advantage of trans fats to the food processing industry is that partial hydrogenation solidifies and stabilizes vegetable oils, which otherwise tend to turn rancid relatively quickly. Because they exist in solid form instead of liquid form, trans fats can be used as substitutes for saturated fats in food products that are meant to have a long shelf life.

Trans fats were invented in the 1890s and began entering the food supply in the 1910s.

However, the use of trans fats in food processing really took off in the 1970s and 1980s, when it was saturated fats were deemed to be bad for health.

Because trans fats were derived from vegetable oils, for many years it was assumed that they would be healthy food products.

    What Is Unhealthy About Trans Fats?

    Unfortunately, as it turns out (and as we were relatively slow to learn), trans fats increase total cholesterol levels and LDL cholesterol levels; worse (and in contrast to saturated fats), they reduce HDL cholesterol levels. Trans fats also appear to interfere with the body's usage of omega-3 fatty acids, which are important for heart health.

    In other words, trans fatty acids are bad for cardiovascular health.

    In fact, it now appears quite evident that trans fatty acids are far worse for cardiovascular health than saturated fats. Indeed, the old dogma about whether saturated fats pose a serious risk to cardiovascular health has now been questioned. In any case, the major push by public health experts to substitute trans fats for saturated fats in our diet is now regarded — by virtually everybody — as a major mistake. 

    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 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.


    Chowdhury R, Warnakula S, Kunutsor S, et al. Association of Dietary, Circulating, and Supplement Fatty Acids with Coronary Risk: a Systematic Review and Meta-Analysis. Ann Intern Med 2014; 160:398.

    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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