No Hiding Most Trans Fats

The current federal food-labeling law requires that manufacturers identify the major nutrients in processed foods, including total fat. Moreover, the law mandates that the “Nutrition Facts” section of each label separately list nutrients that can pose significant health risks, such as saturated fats. Last week, the Food and Drug Administration announced that beginning in 2006, it will require food processors and dietary-supplement makers to also reveal quantities of another notorious member of that family: trans fats.

Pastries are a major hidden source of trans fats in the modern diet.
A sample food label depicting how the trans fats content of processed food will be displayed. FDA

Some 500,000 people die in the United States each year from coronary heart disease, which is usually caused by heart arteries getting clogged with fatty plaque. A primary risk factor for developing this plaque is elevated blood concentrations of cholesterol carried in low-density-lipoprotein (LDL). LDL cholesterol is known as the bad type because it can invade vessel walls, where it evolves into plaque. Eating saturated fat tends to raise blood concentrations of LDL.

Although people have gotten the message that large quantities of saturated fats are unhealthy, most consumers know relatively little about trans fats. In fact, “trans fats are worse for cholesterol levels than saturated fats,” according to a background paper from the Harvard School of Public Health. Why? Eating trans fats not only elevates LDL cholesterol, but also actually compounds that risk by also lowering blood concentrations of high-density-lipoprotein (HDL) cholesterol, the so-called good type. HDL helps ferry cholesterol out of the bloodstream and to the intestine, where it’s eliminated.

“Detailed research–particularly that done at Harvard–shows that the total amount of fat in the diet, whether high or low, has no real link with disease. Rather, what really matters is the type of fat in the diet,” according to the Harvard background report.

Under the new FDA rules, manufacturers and bakers will have to identify trans fats wherever they occur in amounts of 0.5 gram or more. The rules will permit food processors to make new claims on their labels, such as “low in trans fat” or “low in cholesterol-raising fat.” The rules also change the qualifications for “lean” and “extralean” claims on food packaging. The calculations of fat content for those designations will include trans fats, which FDA hasn’t always required.

If consumers pay attention to these labels and limit their intake of trans fats, FDA estimates that its new rules “will save between $900 million and $1.8 billion each year in medical costs, lost productivity, and pain and suffering.” Indeed, FDA announced it is also considering requiring a footnote to the Nutrition Facts labeling that:

  • recommends people limit not only their daily intake of total fats, but also their intake of saturated and trans fats.
  • discloses the role of certain fats in raising blood cholesterol concentrations and how to use this information to create a heart-healthier diet.

Where to find trans fats

The simplest fats are saturated, which means they’re straight-chain molecules usually containing 8 to 20 segments. Structurally, they resemble centipedes. The backbone of a saturated fat’s structure is a string of carbon atoms, each attached to its neighbors with what are known as single bonds. Also attached to each carbon atom is a pair of hydrogen atoms–one on each side, like the centipede’s legs.

In nature, most fats aren’t made from such strings of single-bonded carbons. The majority has at least one double bond between carbons at positions where two adjacent centipede legs are missing. Wherever these more rigid double bonds develop, the molecule suddenly bends or kinks. Such fats, called unsaturated, are the natural form of most fats in plants.

Because straight-chained, saturated fat molecules lay together more compactly, they’re solid at room temperature. Through a chemical process known as hydrogenation, however, liquid vegetable oils can be partially de-kinked and transformed into trans fat that also stay solid at room temperature. This has made trans fats a convenient and inexpensive surrogate for butter and lard. Indeed, trans fats made vegetable shortenings and stick margarines possible.

Over the past few decades, as health research eroded the reputation of saturated fats, food processors turned increasingly to trans fats as a supposedly healthier alternative.

The recognition that trans fats are at least as bad for a person’s heart as saturated fats are (SN: 8/10/96, p. 87) has fueled the development of soft margarines that carry little or no trans or saturated fats. Although these have become popular with a small subset of health-conscious consumers, their higher cost and poorer performance in cooking and baking explains the reluctance of commercial cooks and food processors to substitute them for trans-fat-based vegetable shortenings and margarines.

Not surprisingly, most trans fats in U.S. diets come from crackers, candies, snack foods, fried foods, baked goods, and other processed foods made with shortening and margarines.

And then there’s CLA

What the Harvard report and most news accounts on the FDA labeling announcement fail to note is that even with trans fats, all are not created equal. There is a family of trans fats, known as conjugated linoleic acids (CLAs), that not only appear to fight heart disease, but also cancer, obesity, and diabetes (SN: 3/3/01, p. 136: The Good Trans Fat).

The double bonds in these trans fats–and thus, their kinks–occur in unusual positions. Some CLAs occur naturally in dairy products, especially milk and butter. Others form as a result of chemical processing or cooking.

The radically different health effects–possible health benefits–associated with these unusual trans fats weren’t lost on the FDA. In its July 11 Federal Register announcement of the trans fats-labeling regulation, it noted that CLAs are “metabolized differently” from other trans fats. “Under FDA’s definition, conjugated linoleic acid would be excluded from the definition of trans fat,” the announcement says.

Janet Raloff is the Editor, Digital of Science News Explores, a daily online magazine for middle school students. She started at Science News in 1977 as the environment and policy writer, specializing in toxicology. To her never-ending surprise, her daughter became a toxicologist.

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