Food rich in unhealthy trans fats, like those found in fast food restaurants, are even more dangerous to women than previously believed, according to new research. That study finds that women who regularly consume these heart-hurting fats have three times the risk of heart disease as those with the lowest intake.

"This study just reinforces the idea that trans fat is bad—worse than saturated fat—and we need to make a concerted effort to reduce trans fats," says Dr. Frank Hu, senior author of the study and an associate professor of nutrition and epidemiology at the Harvard School of Public Health in Boston.

The Impact

Trans fats, also called hydrogenated fats, are man-made compounds made from processed liquid oils. These harmful fats will raise bad cholesterol and could lower a person's good cholesterol levels. Because these fats are so thick and stiff, they can also clog up arteries and blood vessels, which can lead to heart attack or stroke.

These fats are commonly found in processed foods such as potato chips, cookies, doughnuts, cakes and many fast foods.

Previous research had already implicated dietary trans fat as a major player in the development of heart disease. However, past research had been done using self-reported dietary information.

The Study

Hu's new study includes an objective measure of trans fat intake—levels found in red blood cells. He notes that because red blood cells live for six months or more, trans fat levels in those cells are a good indicator of average trans fat intake.

His Harvard team examined blood samples collected from almost 33,000 women participating in the ongoing Nurse's Health Study. During the six-year study period, 166 women developed heart disease. The researchers then pulled information on 327 healthy women to serve as controls. Men were not studied.

The women were grouped into four different quartiles based on the levels of trans fats in their blood.

Results: Those with the highest trans fat levels had three times the risk of heart disease when compared with women with the lowest levels. Women in the second and third quartiles had a 60% greater risk of heart disease than those eating the least amount of trans fat.

What Is Too Much?

Hu and his colleagues also estimated the average daily trans fat intake from the trans fat blood levels. Women in the lowest quartile were estimated to consume an average daily trans fat intake of 25 grams, while women in the highest quartile were estimated to take in 3.6 grams per day of trans fats.

These are rough estimates, but the US Food and Drug Administration (FDA) estimates that the average American diet contains about 5.8 grams of trans fat daily. The American Heart Association advises that trans fat should make up no more than 1% of your daily caloric intake.

Trimming The Trans

"Trans fats are a dangerous and unnecessary component of our diet. When you look at data like this, it's scary," says Dr. Nieca Goldberg, medical director of the Women's Health Program at New York University Medical Center and author of The Women's Healthy Heart Program: Lifesaving Strategies for Preventing and Healing Heart Disease in Women. "Just a small change gives you a great increase in risk."

In January 2006, the FDA required labeling changes to list trans fat content. This makes it easier for people to know what's in packaged foods, but it's still difficult to know what's in restaurant or fast foods.

When buying packaged goods, look for foods that have no trans fat. However, under current rules, products with 05 grams or less trans fat can label their products as having zero grams of trans fat. That means if you have four foods with 0.5 grams of trans fat each, you've unwittingly eaten 2 grams.

Given that this study found that averaging just one extra gram daily can significantly increase your heart disease risk, Hu says the labeling is probably "something we should consider."

In the meantime, if a product is labeled zero grams of trans fat, but the ingredient list includes "partially hydrogenated vegetable oil," the food does contain some trans fat, he notes.

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