TUESDAY, Aug. 8, 2006 (HealthDay News) -- Need more proof that a diet high in saturated fats is bad for your heart?
Australian researchers found that eating just one piece of carrot cake high in saturated fat and drinking a milkshake can reduce the body's ability to protect itself against heart disease.
The saturated fat in the cake and the milkshake hampered the ability of the volunteers' "good" cholesterol -- high-density lipoprotein (HDL) -- to do its job. That job is to protect the inner lining of the arteries from inflammatory agents that promote plaque, which clogs the vessels. And the carrot cake and milkshake also reduced the arteries' ability to expand and carry enough blood to organs and tissues, the researchers found.
The take-home message? "Saturated fat meals might predispose to inflammation of and plaque build up in the vessels," said Dr. David Celermajer, Scandrett professor of cardiology at the Heart Research Institute, and Department of Cardiology, Royal Prince Alfred Hospital, University of Sydney.
Celermajer was a co-author of the study that was expected to be published in the Aug. 15 issue of the Journal of the American College of Cardiology.
In the study, Celermajer and his colleagues fed 14 healthy volunteers, ages 18 to 40, two meals eaten a month apart. The volunteers gave blood samples before eating, three hours after eating, and again three hours after that.
They didn't know if they were eating high saturated-fat foods or not. The meals were the same, except one was made with highly saturated coconut oil, and the other with polyunsaturated safflower oil. Each meal featured a slice of carrot cake and a milkshake.
The fat content was high -- about one gram of fat for every 2.2 pounds of body weight. But the meal with safflower oil had about 9 percent saturated fat, while the high saturated-fat meal contained nearly 90 percent saturated fat.
Saturated fat is the main dietary cause of high blood cholesterol, according to the American Heart Association, which recommends limiting saturated fat intake to 7 percent of total calories a day.
The amount of fat in the high-fat meal was equivalent to a 150-pound person eating a double cheeseburger, a large order of fries, and drinking a large milkshake, totaling about 68 grams of fat, the researchers said.
After three hours, the meal high in saturated fat had reduced the ability of the arteries to expand to increase blood flow. The polyunsaturated fat meal reduced this ability slightly as well, but the results weren't statistically significant.
When the researchers sampled the participants' blood six hours after eating, they found that the good (HDL) cholesterol's anti-inflammatory properties had decreased after the saturated fat meal but improved after the polyunsaturated fat meal.
"Our group has measured the anti-inflammatory properties of HDL in this way for years," said Celermajer. "But this is the first time we have studied the effects of any meals on how the HDL might behave."
Alice H. Lichtenstein, senior scientist and director of the Cardiovascular Nutrition Laboratory at Tufts University in Boston, said the study results are "consistent with the current recommendation to restrict saturated fats. They give additional support [for following a diet with healthy fats]. The effects [seen in the study] are transitory," she added, "and there is not enough information on how this would impact cardiovascular risk" in the long run.
Celermajer acknowledged that the effects recorded in the study may be temporary. But, he added, people should be concerned "because it might happen every time they eat a fatty meal -- and thus not be fleeting at all."
Saturated fats aren't the only culprits weighing on America's health. A new review of data from 30 studies conducted over the past four decades identifies increased consumption of sugary drinks as a leading cause of obesity.
According to the study, published in the current issue of the American Journal of Clinical Nutrition, adding just one extra can of soda per day to the diet results in a 15-pound weight gain over the course of a year. Researchers at the Harvard School of Public Health also noted that about a third of all carbohydrate calories in the American diet now come from added sweeteners, with beverages accounting for about half of that amount.
The Harvard team said the evidence strongly supports efforts to discourage consumption of soft drinks and other sugary beverages, especially among children.
In a prepared statement, the American Beverage Association -- which represents the industry -- dismissed the findings. "Blaming one specific product or ingredient as the root cause of obesity defies common sense. Instead, there are many contributing factors, including [lack of] physical activity," the group said.
Meanwhile, another new study reports that diet alone isn't enough to shrink fat cells in the abdomen and reduce the threat of heart disease and diabetes. Exercise must be added to the mix, too, according to preliminary results from a five-year study by Wake Forest University Baptist Medical Center researchers.
"The message is very clear," said Tongjian You, an instructor in geriatric medicine and lead author of the report. "Exercise is important to reducing the size of these cells and may one day be part of a prescription for treating the health complications associated with abdominal fat."
The finding was reported in the August issue of the International Journal of Obesity.
To learn more about fats, visit the American Heart Association.