Objective      To study the effect of different dietary fatty acid compositions on blood lipid metabolism of rats.       Methods      Female SD rats were fed diets containing 15% fat in the experimental period. At age of 48 d

the rats were randomly assigned into 6 groups respectively fed 6 different diets

respectively containing following fatty acids: saturated fatty acid (SFA)

monounsaturated fatty acid (MUFA)

n-6 polyunsaturated fatty acid (PUFA)

n-3 PUFA

1∶1 n-6/n-3 for 18 weeks. The weight was observed every week

and the concentration of blood lipids was measured at end of 8

18 weeks.       Results      Except the obstacle of weight growth in n-3 PUFA group since the 6th week

there was no significant difference among the other groups. As compared with control group at the end of 8 weeks

the serum levels of triglycerol (TG)

total cholesterol (TC)

and low density lipoprotein cholesterol (LDL-C)

TC/HDL-C

LDL-C/HDL-C in n-3 PUFA and 1∶1 n-6/n-3 groups decreased significantly (P0.05)

and high density lipoprotein cholesterol (HDL-C) increased obviously (P0.05); the serum levels of TG

LDL-C

TC/HDL-C in n-6 PUFA group decreased obviously (P0.05); the serum levels of LDL-C in SFA group increased obviously (P0.05). At the end of 18 weeks

the serum levels of TG

TC

and LDL-C

TC/HDL-C

LDL-C/HDL-C in MUFA

n-6 PUFA

n-3 PUFA and 1∶1 n-6/n-3 groups decreased obviously (P0.05)

and HDL-C increased obviously (P0.05)

while the serum levels of these parameters in SFA group increased except increased HDL-C. As compared with 1∶1 n-6/n-3 group

the ratio of LDL-C/HDL-C in MUFA and n-6 PUFA groups decreased obviously (P0.05).        Conclusion      The composition ratio of 1∶1 for n-6/n-3 was the most efficient in decreasing the levels of blood lipids and beneficial to preventing cardiovascular diseases.