Trans fat, a type of fat found in fried foods and processed foods such as cookies, crackers, and donuts, may be worse for the heart than saturated fats, according to a new study. Because the U.S. Food and Drug Administration (FDA) does not currently require information about trans fats on food labels, many Americans do not know how much trans fat they consume. The study found that trans fat reduces blood vessel function and lowers HDL ("good") cholesterol levels more than saturated fat. According to the Center for Science in the Public Interest (CSPI), providing labeling information on trans fats could prevent between 2,100 and 5,600 heart disease-related deaths each year.

Trans fats (also called trans fatty acids) are created by hydrogenation, a process that converts liquid vegetable oils to solid fats at room temperature. This process helps preserve shelf life of foods such as cookies and crackers. Hydrogenation became popular in the 1960s after experts confirmed that animal-based saturated fats increase the risk of heart disease. Many fast food restaurants even stopped cooking French fries in saturated fat and now use hydrogenated vegetable oil (trans fat) instead. However, recent research shows that trans fats also increase the risk of heart disease.

The latest study on trans fats was conducted by Dr. Nicole M. de Roos and her colleagues from Wageningen University in The Netherlands and published in the July 2001 issue of Arteriosclerosis, Thrombosis, and Vascular Biology. The study consisted of 29 healthy, non-smoking adults who were given a four-week diet containing 9.2% of total calories from trans fat. The trans fat diet was followed by another four-week diet containing 9.2% of total calories from saturated fats. After each diet, Dr. de Roos and her colleagues analyzed the effects on blood vessel function. Poor blood vessel dilation can increase the risk for heart disease.

When the researchers compared the effects of both diets they found that the trans fat diet reduced blood vessel function 29% more than the saturated fat diet while HDL ("good") cholesterol levels were 21% lower with the trans fat diet than with the saturated fat diet. This led Dr. de Roos and her colleagues to conclude that trans fats could raise heart disease risk even more than saturated fats (though saturated fats are still bad for the heart too).

Source: American Heart Association

While similar studies and data from the FDA have also shown that trans fats have a negative effect on the heart, the FDA has still not required food manufacturers to provide information specifically about trans fats on food labels (although trans fats are calculated into the total fat listing). Currently, trans fats are technically classified as polyunsaturated fats, though this is misleading because they are not associated with the positive, cholesterol-lowering effects of other polyunsaturated fats such as corn oil. There have been debates about how trans fats would appear on food labels (i.e., whether they would be grouped together with saturated fats) and whether it would then be illegal to market foods with high trans fat as "low cholesterol" or "no cholesterol" items. Previous research has shown that trans fats can also raise LDL ("bad") cholesterol levels.

Concerned consumers who are at risk for heart disease should consider avoiding the purchase of products that contain significant quantities of partially hydrogenated oils. The American Heart Association recommends that people limit their saturated and trans fat intake to less than 10% of their total calories. For people with coronary artery disease, the intake of saturated and trans fat should be less than 7% of their total calories. Total fat, including polyunsaturated fats and monounsaturated fats, should not exceed 30% of total calories for all individuals.

Additional Resources and References

• The study, "Replacement of Dietary Saturated Fatty Acids by Trans Fatty Acids Lowers Serum HDL Cholesterol and Impairs Endothelial Function in Healthy Men and Women," is published in the July 2001 issue of Arteriosclerosis, Thrombosis, and Vascular Biology. An abstract of the study is available at http://atvb.ahajournals.org/
• The July 12, 2001 Reuters Health report, "Trans Fat Worse for Heart Than Saturated Fat," is available within 30 days of publication at http://www.reutershealth.com
• The Center for Science in the Public Interest, a non-profit organization, provides information on trans fats at http://www.cspinet.org/
• To learn more about heart disease, please visit http://www.imaginis.com/heart-disease/

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