More Bad News About Trans Fats
Trans fats might be even more dangerous than previously thought. A new finding, published this week in the journal Circulation, showed that people with the highest levels of the fats in their blood had three times the risk of heart disease of those with the lowest levels.
Researchers conducting the Harvard Nurses' Health Study drew blood samples from more than 32,000 women and also surveyed them on their diet and lifestyle habits. The women were followed for six years to see who developed heart attacks. After controlling for such factors as diabetes, body weight, and alcohol consumption, the team saw a clear link: "The higher the intake of trans fats, the higher the blood levels, and the higher the heart disease risk," says study leader Frank Hu, an associate professor of nutrition and epidemiology at Harvard School of Public Health. Trans fats earned their bad rep by raising "bad" LDL cholesterol and lowering "good" HDL cholesterol. The average intake for those with the highest blood levels was about 4 grams of trans fats per day.
Using a complex laboratory technique, the researchers analyzed red blood cells to measure the amount of trans fats forming the structure of the cell membrane; since red blood cells live for months, Hu explains, this was a way to assess the impact of trans fat intake over an extended period. Previous studies, which have looked only at dietary habits in relation to heart disease risk, have estimated an increased risk of about 25 to 35 percent in those who ate the most trans fats. Now, that appears to be an underestimation, Hu says.
Cholesterol screenings and other routine blood tests can't measure the amount of trans fats in a person's blood. But the study adds to the case for strictly limiting intake. The American Heart Association recommends keeping trans fats under 1 percent of your total calories, or a maximum of 2 grams a day in a 2,000-calorie diet. That means avoiding anything with partially hydrogenated oils, such as margarine. Choose monounsaturated fats found in olive oil and canola oil, recommends Robert Eckel, immediate past president of the American Heart Association and a professor of medicine at the University of Colorado at Denver and Health Sciences Center. Butter, lard, and tropical oils like coconut and palm oil are not good substitutes. They're loaded with saturated fat, which, like trans fats, raises LDL cholesterol. "The AHA takes the position," Eckel says, "that these are just as bad as trans fats."