Overall , high-walnut-enriched diets significantly decreased total and LDL cholesterol for the duration of the short-term trials .
BACKGROUND Consumption of nuts has been associated with a decreased risk of  cardiovascular disease events  and death .
Walnuts in particular have a unique profile : they are rich in polyunsaturated fatty acids , which may improve blood lipids and other cardiovascular disease risk factors .
OBJECTIVES We aim ed to conduct a literature review and a meta- analysis to combine the results from several trials and to estimate the effect of walnuts on blood lipids .
Effects of walnuts on serum lipid levels and blood pressure in normal men.
BACKGROUND In a recent six-year follow-up study , we found that frequent consumption of nuts was associated with a reduced risk of ischemic heart disease .  To explore possible explanations for this finding , we studied the effects of nut consumption on serum lipids and blood pressure . METHODS We r and omly placed 18 healthy men on two mixed natural diets  , each diet to be followed for four weeks . Both diets conformed to the National Cholesterol Education Program Step 1 diet and contained identical foods and macronutrients , except that 20 percent of the calories of one diet ( the walnut diet ) were derived from walnuts ( offset by lesser amounts of fatty foods , meat , and visible fat [ oils , margarine , and butter ] ) . RESULTS With the reference diet , the mean ( + /- SD ) serum values for total , low-density lipoprotein ( LDL ) , and high-density lipoprotein ( HDL ) cholesterol were , respectively , 182 + /- 23 , 112 + /- 16 , and 47 + /- 11 mg per deciliter ( 4.71 + /- 0.59 , 2.90 + /- 0.41 , and 1.22 + /- 0.28 mmol per liter ) . With the walnut diet , the mean total cholesterol level was 22.4 mg per deciliter ( 0.58 mmol per liter ) lower than the mean level with the reference diet ( 95 percent confidence interval , 28 to 17 mg per deciliter [ 0.72 to 0.44 mmol per liter ] ) ; the LDL and HDL cholesterol levels were , respectively , 18.2 mg per deciliter ( 0.47 mmol per liter ) ( P < 0.001 ) and 2.3 mg per deciliter ( 0.06 mmol per liter ) ( P = 0.01 ) lower . These lower values represented reductions of 12.4 , 16.3 , and 4.9 percent in the levels of total , LDL , and HDL cholesterol , respectively . The ratio of LDL cholesterol to HDL cholesterol was also lowered ( P < 0.001 ) by the walnut diet .  Mean blood-pressure values did not change during either dietary period . CONCLUSIONS Incorporating moderate quantities of walnuts into the recommended cholesterol-lowering diet while maintaining the intake of total dietary fat and calories decreases serum levels of total cholesterol and favorably modifies the lipoprotein profile in normal men . The long-term effects of walnut consumption and the extension of this finding to other population groups deserve further study
Overall , high-walnut-enriched diets significantly decreased total and LDL cholesterol for the duration of the short-term trials .
BACKGROUND Consumption of nuts has been associated with a decreased risk of  cardiovascular disease events  and death .
Walnuts in particular have a unique profile : they are rich in polyunsaturated fatty acids , which may improve blood lipids and other cardiovascular disease risk factors .
OBJECTIVES We aim ed to conduct a literature review and a meta- analysis to combine the results from several trials and to estimate the effect of walnuts on blood lipids .