Sunflower oil favorably alters low cholesterol

Nutrition Research Newsletter, August, 2005

The relationship between diets high in saturated fat with elevations of plasma cholesterol and risk of coronary heart disease has resulted in nutrition recommendations to decrease dietary fat intake to no more than 25% to 35% of energy, with saturated fat replaced by dietary carbohydrate or unsaturated fat. It is now increasingly recognized that substitution of carbohydrate with monounsaturated fat is an alternative approach and may be more desirable. One prospective, randomized controlled trial indicates that the Mediterranean-style diet prevents myocardial infarction. One characteristic of this diet is the use of monounsaturated fat rather than saturated fat, although other properties of the diet, such as increased amounts of n-3 fatty acids, may be responsible for the observed clinical effects. The aim of this study was to replace saturated fat with monounsaturated fat and measure dietary-induced changes in factor VIIc, fibrinogen, PAI-1, cholesterol, triglycerides, and apolipoproteins A-1 and B. Previous studies demonstrating changes in these variables have generally used olive oil and canola oil as the sources of monounsaturated fat. This study uses high-oleicacid sunflower oil as the source of monounsaturated fat. This was to determine whether some favorable properties are restricted to olive oil and to avoid the a-linolenic acid content of canola oil that may have its own effects on triglyceride levels and hemostatic factors.

Subjects were randomly allocated to two groups. The study design was an ABB/BAA extra-period crossover. One group consumed a diet rich in saturated fatty acid (SFA) with fat making up 20.8% of total energy, for 5 weeks and then one rich in monounsaturated fatty acid (MUFA), with fat making up 20.3% of total energy for 10 weeks. The other group consumed the MUFA diet for 5 weeks followed by the SFAdiet for 10 weeks. Men and women aged 35 years to 69 years, who were nonsmokers with no chronic illness and not on any medication were recruited to participate. Eighteen subjects were recruited and 15 (5 men, 10 women) completed the community-based study. Blood was sampled at the beginning and end point of each 5-week diet period for analysis of coagulation and fibrinolysis factors and blood lipids. Subjects kept 3-day food diaries twice during each of the three diet periods and were weighed on each visit for blood collection. Analysis of plasma fatty acids was used to indicate dietary compliance.

The subjects selected a diet lower in fat than that in which they had been educated. However, the percentage energy from protein, carbohydrate, and fat and the total dietary fiber intake were the same on both diets. The lower fat intake was consistent throughout the three diet periods and a differential between the monounsaturated fat intake on the two diets of 10.7% of total energy intake was achieved. Cholesterol intake was higher on the SFA-rich diet because the butter and stearine contributed cholesterol and the high-oleic-acid sunflower oil has none.

Triglyceride concentrations were lower on the MUFA-rich diet. It is recognized that using monounsaturated fat rather than carbohydrate to replace the energy from saturated fat, results in a lowering of triglycerides. A growing number of studies confirm that substituting saturated fat with a variety of monounsaturated fats, including olive oil, peanut oil, peanuts and peanut butter, and macadamia and pecan nuts will lower plasma triglycerides. The reduction of 14% in this study with high-oleic-acid sunflower oil concurs well with the 13% reduction observed with olive oil as the source of monounsaturated fat. A number of mechanisms have been proposed for the observed effect of high MUFA diets on triglyceride concentrations, including changes in the composition of very-LDL cholesterol and in the processing and catabolism of very-LDL cholesterol. Substituting foods rich in saturated fat with foods rich in high-oleicacid sunflower oil and margarine with a high content of monounsaturated fat has favorable outcomes on blood lipid profiles and factor VIIc. Although it did not result in a lowering of PAI-1 activity, as previously reported with olive oil, high-oleic-acid sunflower oil presents another useful source of monounsaturated fat. Factor VIIc was lower on the MUFA diet, but fibrinogen and insulin concentrations and plasminogen activator inhibitor-1 activity did not differ between diets. Low-density lipoprotein cholesterol and triglyceride levels were lower on the MUFA diet compared with the SFA diet. A significant increase in both plasma phospholipid and neutral lipid oleic acid occurred on the MUFA diet.

Substitution of foods rich in saturated fat with foods rich in high-oleic-acid sunflower oil and margarine has favorable outcomes on blood lipids and factor VIIc. This oil presents another useful source of MUFA for diets aimed at prevention of heart disease.

Allman-Farinclli M. A., Gomes K., Favaloro E. J., Petocz R A Diet Rich in High-Oleic-Acid Sunflower Oil Favorably Alters Low-Density Lipoprotein Cholesterol, Triglycerides, and Factor VII Coagulant Activity. JADA; 105(7): 1071-1079 (July 2005). [Correspondence: Emmanuel J. Favaloro, PhD, Department of Haematology, Institute of Clinical Pathology and Medical Research, WSAHS, Westmead, NSW 2145 Australia]