Title: The Effect of Walnuts Compared to Fish on Lipids and Fatty Acids in Blood
This study was a carefully controlled feeding study that spanned the course of 14 weeks. It was completed with 25 participants between the ages of 20 and 65. All participants were randomly assigned to one of three groups: the control group, the walnut-rich group, or the fish group. The study diets closely followed the recommendations of the American Dietetic Association Food Guide pyramid. Those in the fish diet group and walnut-rich group consumed the same diet as that of the control group with minor modification. The fish group received an omega-3 rich fish as a substitute for the meat in the control diet for two days a week. The walnut-rich diet group consumed approximately 1.5 grams of walnuts each day in addition to their control diet, which was adjusted accordingly. All diets maintained the same caloric levels and nutrient proportions and were tailored appropriately to meet each participant’s nutritional requirements as determined via anthropometric measurements and activity levels. Participants remained in their designated group for 4 weeks at that end of which time blood and urine samples were collected following a 12-hour fast. The groups then switched to one of the other two remaining diets and the process began again until each participant completed all three diets phases.
When compared to the control and fish diets, the walnut diet significantly reduced total cholesterol by 10.8 mg/dL and 18.1 mg/dl and LDL cholesterol by 10.9 Mg/dL and 16.5 mg/dL, respectively. The fish diet significantly increased plasma total and LDL cholesterol compared to the control and walnut diets. The fish diet significantly increased HDL cholesterol and decreased triglyceride compared to both the control and walnut diets. The ratios of total cholesterol: HDL, LDL:HDL and apo B:apo A-1 were all significantly lower after the walnut diet compared to the control and fish diets. The apo B levels decreased after the walnut diet compared to the other two diets, while no differences were observed for apo A-1.
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