What’s Wrong with Trans Fats
By Sheila Buff

In September the Food and Drug Administration (FDA) announced new food label rules that will make food producers list the amount of trans fats in their products as part of the total fat content listing. What exactly are trans fats? And why does the FDA now want them listed on the food label?

Trans fats, also known as partially hydrogenated vegetable oils, are the fats used in just about every kind of commercial baked goods such as cookies and doughnuts, in snack foods such as chips, in many brands of margarine, and in many prepared and frozen foods. They’re also widely used to prepare deep-fried fast foods such as french fries and chicken nuggets. Why? Because trans fats are very inexpensive, they don’t go rancid, and they hold up well to the high temperatures used in frying. And because trans fats are made from vege- table oil, they contain no cholesterol.

If partially hydrogenated vegetable oils were called what they truly are, partially saturated vegetable oils, it would be much easier to understand why they’re so bad for you and why the FDA is now insisting they be listed on the food label. Trans fats are more saturated than natural vegetable oils such as corn oil or canola oil, although they are less saturated than animal fat or butter. What makes trans fats so very dangerous, however, is that in fact they are even worse for your heart than saturated fats. The scientific evidence shows that trans fats raise your total blood cholesterol even more than saturated fats. Even worse, trans fats don’t just raise your LDL (“bad”) cholesterol, they lower your HDL (“good”) cholesterol. In fact, the combined bad effect of trans fatty acids on your LDL/HDL ratio is twice that of saturated fats. Not only that, trans fats raise the level of triglycerides (TG) in your blood. Recent research has shown that the combination of low HDL and high TG raises your risk of heart disease sharply. In fact, low HDL/high TG is probably the most accurate predictor of all that a heart attack is in your future.

Ever since the 1960s, when trans fats became very common in the American diet, researchers have suspected that they were at least one of the culprits in the rising tide of heart disease. The real proof of this didn’t start to come in until the 1980s, and starting in the 1990s, the scientific evidence against trans fats has become much, much stronger.
Two important studies in 1994 from the Harvard School of Public Health showed that overall, the people who eat the most trans fats are also the most likely to develop heart disease. Specifically, their studies showed a strong and significant positive association between trans fat intake and the risk of a having a heart attack. According to these two experts, about 30,000 premature coronary heart disease deaths annually—and possibly as many as 100,000 deaths—can be blamed on consumption of trans fats.

Two later epidemiological studies showed that people who ate the most trans fats had a markedly higher risk of heart disease when compared to similar people who ate the least trans fats and that the relative risks of heart disease from trans fats were higher than the risks from saturated fats. What makes trans fats raise your blood lipids so much? Researchers still aren’t sure, but the current thinking is that these fats are so unnatural that your body isn’t designed to deal with them. Other researchers believe that trans fats in the cell membrane interfere with other normal cell functions. Trans fats may also affect your body’s use of essential fatty acids by interfering with or blocking some crucial pathways, such as hormone production.

Pretty convincing, isn’t it? The FDA thinks so. Until the new regulations go into effect in couple of years, however, you’re on your own when it comes to finding—and avoiding—the trans fats in foods. Here’s a useful hint for guesstimating based on the food label: Look at the total fat grams listed on the label and subtract the saturated fat grams. What’s left is a good estimate of the amount of trans fats in the food.

Sheila Buff is a freelance writer specializing in medicine, health, and nutrition. She lives in Milan. She is the author of The Good Fat, Bad Fat Counter (St. Martin’s Press, 2002, paperback, $4.99), on which part of this article is based.