While a diet rich in butter, fatty meats, and cheeses may taste great to many, doctors have warned about the potential damage those foods do to the heart for years. Now, a new study contends that health experts have been looking at saturated fats all wrong. A team from the University of Bergen says foods high in saturated fat may not actually lead to heart disease.
Despite the belief that saturated fats block the arteries, the study reveals cholesterol is actually vital for keeping cells healthy.
Researchers say when people remove these foods from their diets, they need to eat more products high in polyunsaturated fats to get the same benefits that come from having a smaller amount of saturated fats. These substitutes include sunflower oil, walnuts, and fish.
The evidence against saturated fat is ‘unconvincing’
The Norwegian team discovered some saturated fats occur naturally in a wide variety of foods, including breast milk. The scientists say people with high cholesterol who suffer cardiovascular disease may actually have low-grade inflammation and insulin resistance. They also question the benefit of lowering blood cholesterol by adding polyunsaturated fatty acids to the diet and not addressing the root causes.
“There is at best weak evidence that a high intake of saturated fat causes heart disease,” study co-author Simon Dankel says in a media release. “The overall data are inconsistent and unconvincing, not to mention the lack of a logical biological and evolutionary explanation. Also, people with metabolic disorders often do not show the expected changes in blood cholesterol when changing their fat intake, suggesting loss of the normal response.”
“Cholesterol is a critically important molecule for all cells in the body,” adds lead author Marit Zinöcke from Bjørknes University College in Oslo.
How do the cells make good use of cholesterol
“A cell is surrounded by a fluid membrane that controls cell function, and the cells depend on the ability to incorporate a certain amount of cholesterol molecules, so that their membranes don’t become too stiff or too fluid. The basis of the model is that when saturated fats replace polyunsaturated fats in the diet, less cholesterol is needed in the cell membranes,” Zinöcke explains.
Zinöcke notes that the opposite is true when people eat more polyunsaturated fatty acids, which include omega-3 and omega-6 fatty acids. When polyunsaturated fats enter the cell membranes, they make them more fluid. Cells can adjust the fluidity of their membranes by pulling in more cholesterol from the bloodstream. The team believes this is why blood cholesterol levels drop when people eat more polyunsaturated fats.
“Cells need to adjust their membrane fluidity according to changes in their environment, such as the access to different types of fat,” Dankel says. “This phenomenon is called homeoviscous adaptation, and has been described in both microorganisms, vertebrates and in human skin cells. We argue that this is a critical principle in human physiology. Our cells are normally capable of adjusting their cholesterol content according to changes in dietary fats.”
“Nutrition research often focuses on what changes in the body, but the question of why something, such as the blood cholesterol, changes, is of equal importance,” researcher Karianne Svendsen from the University of Oslo concludes.
The findings appear in the American Journal of Clinical Nutrition.
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