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Two Types of Diets Improve Blood Vessel Function in Men with High Cholesterol
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What is the problem and what is known about it so far?
High cholesterol levels can lead to blockages in blood vessels, a condition called atherosclerosis. Atherosclerosis can result in heart attacks or strokes when blockages obstruct blood flow to the heart or brain. The endothelium is the lining of blood vessels, and it helps to control their narrowing and expanding. Endothelium that does not function normally plays a role in the development of atherosclerosis. People can lower their cholesterol levels and their chances of developing atherosclerosis by switching from diets high in saturated fats to diets low in saturated fats. However, it is unclear whether these diets have any effect on the endothelium.
Why did the researchers do this particular study?
To find out if a low-fat diet or a diet enriched with monounsaturated fats (a type of unsaturated fat) affects the endothelium. The low-fat diet was the stage 1 diet that the U.S. National Cholesterol Education Program recommends (the NCEP-1 diet). The diet enriched with monounsaturated fats was the type of diet commonly called a “Mediterranean diet.”
Who was studied?
The study included 22 Spanish men 18 to 65 years of age with high cholesterol levels.
How was the study done?
For the first 28 days of the study, the men ate a diet high in saturated fat. Then, half of the men switched to an NCEP-1 diet and the other half switched to a Mediterranean diet for the next 28 days. After this, the men who had been on the NCEP-1 diet switched to the Mediterranean diet and vice versa for the last 28 days of the study. At the end of each of the diets, the researchers collected blood samples to measure cholesterol and other fats in the blood. They also studied the endothelial function of each man using special ultrasound tests of the blood vessels.
What did the researchers find?
Compared with the diet high in saturated fat, both the NCEP-1 and Mediterranean diets resulted in lower levels of cholesterol and other fats in the blood. Endothelial function was generally improved with both the NCEP-1 and Mediterranean diets. However, only the Mediterranean diet resulted in improvements in one type of measure of endothelial function called “flow-mediated vasodilation.” Flow-mediated vasodilation is the amount that blood vessels expand as blood flow increases.
What were the limitations of the study?
This study included only men with high cholesterol, so the results might not apply to women or to people with lower cholesterol levels. It is not known whether the results would be similar in people who stayed on the diets for longer than 28 days.
What are the implications of the study?
Compared with diets high in saturated fat, NCEP-1 and Mediterranean diets improve endothelial function and lower cholesterol in men with high cholesterol levels.
Article and Author Information
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The summary below is from the full report titled “Mediterranean and Low-Fat Diets Improve Endothelial Function in Hypercholesterolemic Men.” It is in the 19 June 2001 issue of Annals of Internal Medicine (volume 134, pages 1115-1119). The authors are F Fuentes, J López-Miranda, E Sánchez, F Sánchez, J Paez, E Paz-Rojas, C Marín, P Gómez, J Jimenez-Perepérez, JM Ordovás, and F Pérez-Jiménez.
- Copyright ©2004 by the American College of Physicians
