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July Newsletter

Trans Fatty Acids

By David Mendosa

Last Update: September 23, 2001

We thought all along that saturated fat was the worst for us. We switched from butter and all its saturated fat to margarine. Guess what? The trans fatty acids in margarine and many other foods is the worst choice we can make.

The worst are trans fatty acids.

Hot News in Diabetes
Carbohydrates aren't the only culprits. Diabetes is a disease where carbohydrate metabolism doesn't work correctly, but it turns out that some types of fat are also to blame.

The new findings come from the Nurses' Health Study, which relates diet and lifestyle factors to chronic disease incidence in female registered nurses. Jorge Salmerón and six co-authors followed the 84,204 women who had filled out a questionnaire in 1980. During 14 years of follow-up, 2,507 nurses got type 2 diabetes.

Their article, "Dietary fat intake and risk of type 2 diabetes in women" in the June 2001 issue of The American Journal of Clinical Nutrition for the first time shows the relative risk of different types of fat. The results have astounded even the professionals.

We all knew that saturated fat was the worst. To the contrary, the study found that intake of saturated fatty acids were not significantly associated with the risk of diabetes. Neither were monounsaturated fatty acids (such as olive oil) or even total fat intake.

The worst, in fact, are trans fatty acids. Dietary cholesterol is also associated with increased risk of diabetes.

"We speculate that the effects of dietary trans fatty acids and cholesterol are not sufficient to cause diabetes," the study says, "but in the presence of underlying insulin resistance may increase the probability of developing clinical disease."

About 95 percent of trans fatty acids come from partially hydrogenated vegetable oil. They make it when they heat vegetable oils in the presence of metal catalysts and hydrogen.

On the other hand, one type of fat actually reduces the risk of diabetes. "Polyunsaturated fatty acid intake was associated with a substantial reduction in risk," the study found.

Lifestyle Improvement Tip
There's not a word in the new study about the effects of the different types of fat on people who already have diabetes. But there is no reason to believe that those fats associated with the risk of developing diabetes are any better for those of us who already have the disease.

We need to limit our intake of trans fatty acids more than any other type of fat. It is related not only to an increased risk of diabetes but also to coronary heart disease, according to a 1999 report in The New England Journal of Medicine.

Where do you find trans fatty acids? For now, you need to read the "Ingredients" list on the label. But it usually won't say "trans fatty acids." Look for "partially hydrogenated" oils.

The "Nutrition Facts" on the label may soon require that the amount of trans fat be added to the amount of saturated fat. The Food and Drug Administration has proposed that rule.

Trans fat is found in vegetable shortenings, some margarines, crackers, cookies, and many other foods made with or fried in partially hydrogenated fats. The FDA's Web site has a valuable table showing how many grams of trans fat per serving we get from 16 of the most loaded foods.

Worst is pound cake with 4.3 grams per serving. Then, on the basis of the upper level of the range, come vegetable shortening, doughnuts, french fries, and stick margarine.

Related Web Site Reviews
Jorge Salmerón et al. "Dietary fat intake and risk of type 2 diabetes in women," The American Journal of Clinical Nutrition, Vol. 73, No. 6, pp. 1019-1026, June 2001.

An abstract of this article is free on-line at and the full-text is $8.

This study concludes total fat, saturated fat, and monounsaturated fatty acid intakes are not associated with risk of type 2 diabetes in women. But we could substantially reduce the risk of type 2 diabetes if we substituted nonhydrogenated polyunsaturated fatty acids in our diet for trans fatty acids.

Alberto Ascherio et al. "Trans fatty acids and coronary heart disease." The New England Journal of Medicine, Vol. 340, No. 25, pp. 19948, June 24, 1999.

The full text of this article is free on-line at

On a per-gram basis, the adverse effect of trans fatty acids on coronary heart disease appears to be stronger than that of saturated fat. Although changes in labeling are important, the authors believe that they are not enough. That's because many fast foods, which are exempt from labeling regulations, contain high levels of trans fatty acids, and can even be advertised as cholesterol-free and cooked in vegetable oil.

U. S. Food and Drug Administration, "Questions and Answers on Trans Fat Proposed Rule," November 1999, on-line at .

Together with a linked press release and fact sheet, the FDA provides a primer on the known problems with fatty acid even before researchers discovered that it is associated with diabetes. FDA based its proposal on studies that indicate consumption of trans fatty acids contributes to increased blood LDL-cholesterol ("bad" cholesterol) levels, which increase the risk of coronary heart disease.

Trans Fatty Acids in One Serving of Selected Foods

Trans fat is found in vegetable shortenings, some margarines, crackers, cookies and many other foods made with or fried in partially hydrogenated fats. The following information is from a 1995 report from the U.S. Department of Agriculture found on the FDA Web site. This information is the most recent database available on the content of trans fatty acids in foods. 

Food Trans Fatty Acids

Vegetable shortening


Margarine (stick)


Margarine (tub, regular)


Salad dressings (regular)


Vegetable oils


Pound cake




Microwave popcorn (regular)


Chocolate chip cookies


Vanilla wafers


French fries (fast food)


Snack crackers


Snack chips


Chocolate candies


White bread


Ready-to-eat breakfast cereals


This article was originally written for the LXN Corp. Web site.

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