Trans Fats Are Bad, Aren't They? | Science News

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Food for Thought

Janet Raloff
Food for Thought

Trans Fats Are Bad, Aren't They?

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The media have been rife with reports on trans fats since New York City's Board of Health announced it would phase out these fats in restaurants and other food-service establishments. And that's good news for most consumers because trans fats can pose a double whammy for the heart. Not only can they hike a person's bad cholesterol even more than saturated fats can, but they also reduce concentrations of the good cholesterol in blood.

Not surprisingly, these largely synthetic fats—designed to stay solid at room temperature, as saturated fats do, and typically used in fried foods and bakery items—have been linked to ailments ranging from coronary heart disease to diabetes (SN: 11/10/01, p. 300).

So, good riddance. Right?

Well, as with so much in science, there are caveats. And there's a big one with the trans fats. Although the vast majority of these fats are unhealthy, there is a minority that are fine to eat and may even prove beneficial.

Known as conjugated linoleic acids (CLAs), some of these trans fats occur naturally in dairy products and meat, especially milk and butter. Others form as a result of chemical processing or cooking. A growing number of studies have demonstrated that, at least in animals, these unusual fats fight a host of chronic health conditions from heart disease to diabetes to cancer (SN: 3/3/01, p. 136). Most recently, several CLAs have shown promise in moderating the runaway inflammation that underlies arthritis, asthma, and even lupus (see Inflammation-Fighting Fat).

A new line of research now aims at naturally increasing the concentrations of these unusual trans fats in foods such as milk and cheeses. Michael W. Pariza of the University of Wisconsin–Madison, who discovered the beneficial alter ego of CLA trans fats more than 2 decades ago, suspects that one day they may even be added to foods to fortify their healthiness.

At present, however, most people take in minimal amounts of CLAs.

Nevertheless, data on the potential benefits of these unusual trans fats have been so compelling that the Food and Drug Administration exempted them from the new trans-fat labeling law that went into effect this year (see No Hiding Most Trans Fats). That law had been intended to steer people away from bad fats.

Meanwhile, research continues to malign the synthetic trans fats being targeted by New York City and other health departments. For instance, a major review of the health implications of current U.S. consumption patterns of trans fats appeared in the April 13 New England Journal of Medicine. Walter C. Willett of the Harvard School of Public Health, in Boston, and his colleagues reported that some 2 to 3 percent of people's daily calories typically come from the synthetic trans fats.

Willett's team found that largely eliminating bad trans fats in U.S. diets could improve people's blood cholesterol enough to cut heart attacks and other cardiovascular problems by 3 to 6 percent. That would be up to 72,000 fewer such adverse events per year, the team said. Even better, other advantages from such a dietary shift, such as improved immune systems, could eliminate another 150,000 or so adverse heart events per year.

The team's report also briefly addresses CLAs and notes that they aren't the kind of trans fats that researchers are worried about.

There is one more important caveat about CLAs: As fats, they're high in calories. That means that, as with all energy-dense foods, consumption of their food sources should be kept within moderation.

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Further Reading

Gorman, J. 2001. Trans fats. Science News 160(Nov.10):300-301. Available at [Go to].

Ascherio, A., M.J. Stampfer, and W.C. Willett. 2006. Trans Fatty Acids and Coronary Heart Disease. Harvard School of Public Health report (with update). Available at [Go to].

Raloff, J. 2005. Inflammation-fighting fat. Science News Online (Oct. 29). Available at [Go to].

______. 2003. No hiding most trans fats. Science News Online (July 19). Available at [Go to].

______. 2001.The good trans fat. Science News 159(March 3):136-138. Available at [Go to].

______. 1999. Better butter? This one may fight cancer. Science News 156(Dec. 11):375. Available at [Go to].

______. 1997. Why grass makes for better milk. Science News Online (Oct. 11). Available at [Go to].

______. 1997. Genetically engineering a healthier margarine. Science News Online (May 31). Available at [Go to].

______. 1996. Unusual fats lose heart-friendly image. Science News 150(Aug. 10):87. Available at [Go to].

______. 1995. New trans fat studies muddy the waters. Science News 147(Feb. 25):127. Available at [Go to].

______. 1994. Margarine is anything but a marginal fat. Science News 145(May 21):325.

______. 1994. This fat may fight cancer several ways. Science News 145(March 19):182-183.

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