As a dietitian, I am sometimes asked if there are foods that I avoid. I think most questioners expect me to curse excess sugar/salt/fat/carbohydrates or to give a long-winded commentary about how everything should be in moderation. They are usually surprised when I say that I always check for trans fats. So, imagine the way my ears perked up when I heard a news story yesterday about how the FDA is proposing to remove all trans fats from the food supply.
So, what are trans fats and why are they so bad? You may have already heard of unsaturated and saturated fats. Basically, this is referring to whether the long carbon chains that make up fatty acids (which are the building blocks for fats) are “kinked” or not, based on how many hydrogen atoms are attached to the carbons. Looking at the graphic below, you can see that the first structure is just a bunch of carbon atoms together in a straight line; this is because it is fully hydrogenated. Compare that to the last structure, which is an unsaturated fatty acid, where there are two hydrogen atoms missing from two of the carbon atoms, leading to a double bond (anyone getting organic chemistry flashbacks?) and causing a “kink” in the chain. The middle structure is also missing two hydrogen atoms, but there’s no “kink” because the missing hydrogens are on opposite sides (trans configuration) of the carbon atoms whereas cis-configured unsaturated fatty acids have their hydrogen atoms missing from the same side, effectively kinking the fatty acid.
Why does this matter? Well, due to the “kink” in the carbon tail of unsaturated fats, they can’t pack very closely together, which is why unsaturated fats like olive or canola oils are liquid at room temperature. Saturated fats, because their carbon tails are straight, can squeeze together, so they are solid at room temperature, like butter. Trans fats are unsaturated, but because there are no kinks, they can also pack closely together, resulting in things like margarine and Crisco.
While trans fats are found in nature in some meat and dairy products, they are mostly the product of food processing (hydrogenation – forcing hydrogen atoms onto unsaturated fatty acids); the vast majority of trans fats consumed by humans are man-made. Trans fats are shelf-stable and more inexpensive than other fats, which makes them appealing to the food industry. Consumption has been linked to heart disease, especially coronary artery disease, where plaques can build up in the arteries. The CDC estimates that “avoiding artificial trans fat could prevent 10,000-20,000 heart attacks and 3,000-7,000 coronary heart disease deaths each year in the U.S.”
So, until we finally hear about whether the FDA will prevail or not, what can you as a consumer do?
Currently, the FDA permits a product to be labeled as having 0 grams of trans fats if there is less than 0.5g trans fat/serving. This is so misleading because this loophole allows producers to declare “0 grams trans fat” when the product actually contains it, and it is based on serving size, which most people don’t pay attention to.
Therefore, if, say, a serving of cookies is 2, and each serving has 0.4g trans fat, then if you eat 4 cookies (you must be a better person than me) you’ve consumed 0.8g trans fat. The American Heart Association recommends “limiting the amount of trans fats you eat to less than 1 percent of your total daily calories. That means if you need 2,000 calories a day, no more than 20 of those calories should come from trans fats. That’s less than 2 grams of trans fats a day.” Now, consider everything else you might be eating throughout the day and how that may affect your trans fat intake.
Due to the labeling loophole, the best way to tell whether your favorite processed food contains trans fat is to look at the ingredient list (dietitian pro-tip: always check out the ingredient list!). If “partially hydrogenated cottonseed/soybean/palm/coconut/anything oil” is on the list (like below), put it back on the shelf and slowly back away (go check out the produce aisle!). This FDA page has really great information meant for consumers.
There you have it. I am a proponent of moderation (sorry, had to slide that in here) so you’ll find me eating all sorts of foods, but if I’m going to eat any processed foods, I always check for the presence of trans fats. If they’re there, they’re out.