THURSDAY, Feb. 12, 2015 (HealthDay News) -- People who follow a heart-healthy diet won't see much change in their eating habits if, as reported, this year's U.S. Dietary Guidelines report rescinds previous warnings against eating certain cholesterol-rich foods, dietitians say.
That's because people still need to limit their consumption of saturated fats and trans fats, which are the two leading dietary contributors to high blood cholesterol.
The proposed change in the guidelines "doesn't give you free license to eat as much high-cholesterol food as you want, because those foods most often are high in saturated fat as well," said Connie Diekman, a registered dietitian and director of university nutrition at Washington University in St. Louis.
Only a handful of common foods are high in cholesterol but low in saturated fat -- eggs, shellfish and liver, mainly, Diekman said.
People looking to eat a heart-healthy diet will still have to avoid foods such as fatty cuts of meat, and cheese or ice cream made from whole milk, because those are high in saturated fat. Same goes for bacon, fried chicken, hot dogs and cheeseburgers.
They also will have to avoid processed foods high in trans fats due to ingredients like partially hydrogenated vegetable oils -- think packaged cookies and cakes. Trans fats have been shown to simultaneously increase levels of "bad" LDL cholesterol in the blood and decrease levels of "good" HDL cholesterol, experts say.
Much confusion has arisen from published reports Tuesday that a U.S. Department of Agriculture panel is preparing to bow to new research that has undermined the role that dietary cholesterol plays in a person's heart health.
The Dietary Guidelines Advisory Committee plans to drop limits on dietary cholesterol intake when it issues its 2015 update of the USDA Dietary Guidelines, according to news reports.
Cholesterol is an organic molecule naturally produced by humans and animals. A waxy substance, cholesterol is used by the body to create hormones, produce bile acids for digestion, make vitamin D and maintain healthy cell walls, according to the U.S. National Institutes of Health.
Healthy human bodies control the amount of cholesterol in the bloodstream, and can detect and adjust its natural cholesterol production if dietary cholesterol (cholesterol consumed in foods) increases or decreases, Diekman said.
"If we've consumed more cholesterol than we need, we just make less," Diekman said. "We have a self-regulating mechanism for cholesterol."
The body also can excrete unneeded dietary cholesterol, particularly if the person is eating a fiber-rich diet, said Lona Sandon, an assistant professor of clinical nutrition at the University of Texas Southwestern Medical Center at Dallas. Fiber -- found in foods such as fruits, vegetables, nuts, oatmeal and whole grains -- binds to dietary cholesterol in the digestive tract and keeps it from being absorbed into the bloodstream.
But when folks eat saturated fats, they do an end-run around the body's self-regulating system for maintaining healthy cholesterol levels, the nutritionists said.
During digestion, saturated fats are absorbed into the bloodstream and transported to the liver, where they are converted into "bad" LDL cholesterol, said Sonya Angelone, a registered dietitian nutritionist in San Francisco and a spokeswoman for the Academy of Nutrition and Dietetics.
Taking in too much saturated fat, therefore, can lead to overproduction of LDL cholesterol, and unhealthy levels of blood cholesterol. "The more fat you have available to make cholesterol, you're going to make more cholesterol than you need," Sandon said.
Saturated fats are found primarily in animal-based foods like meat, poultry, swine and dairy products. They are solid at room temperature -- for example, the fat around the edge of a steak, a stick of butter, or a can of lard.
High levels of "bad" LDL cholesterol in a person's blood have long been linked to the formation of arterial plaques that can impede the flow of blood and contribute to heart attacks or strokes, according to the American Heart Association.
The reported USDA action reflects a continuing evolution of thought regarding the role of fats in a heart-healthy diet, said Dr. Steve Nissen, a renowned cardiologist and chairman of cardiovascular medicine at the Cleveland Clinic.
For his part, Nissen recommends to his heart patients the only diet that has been tested using a randomized clinical trial -- the Mediterranean diet.
A Mediterranean diet is not low-fat, but emphasizes intake of unsaturated fats from olive oil and nuts, along with lots of vegetables, lean poultry and fish, while avoiding red and processed meats and butter. Unsaturated fats come from plants, and are liquid at room temperature -- for example, olive oil and vegetable oil.
The body converts unsaturated fats into "good" HDL cholesterol, which actually lowers blood cholesterol levels by scavenging free cholesterol from the bloodstream and artery walls, and then ferrying it back to the liver for disposal.
The Mediterranean diet showed a 30 percent reduced risk of heart disease compared to the low-fat diet currently promoted by the American Heart Association, according to clinical trial results published in the New England Journal of Medicine in 2013, Nissen said.
"That's what I think people should use," Nissen said. "We need to rethink all of our dietetic guidelines. Fat is not the problem."
For more on cholesterol, visit the U.S. National Institutes of Health.