1990 年 8 巻 1 号 p. 75-84
The effects of a dietary intake of gamma-linolenic acid 18:3 n-6 (GLA) on blood lipids and phospholipid fatty acids were studied in 25 healthy men. The study was conducted over 4 one-month periods during which the subjects maintained their usual diet of about 2, 780kcal per day consisting of 54.4% carbohydrates, 13.5% proteins, and 32.1 lipids, the last of which included 13% in the form of vegetable oils (40g) and 328mg of cholesterol. The vegetable oil, the only parameter which was varied during the study, was soybean oil during the 1st and 4th periods, not providing GLA, and rapeseed oil and evening primrose oil in the proportion of 2:1 during the 2nd period, providing 1.1g of GLA per day, and 1:1 during the 3rd period, providing 1.6g of GLA per day. The intake of other fatty acids was maintained as constant as possible throughout the study. The administration of GLA was accompanied by a dose-dependent reduction in LDL cholesterol (-10% with 1.1g of GLA and -25% with 1.6g of GLA) and a significant increase in HDL cholesterol (+7 and +9%, respectively). Triglycerides, phospholipids, and apoprotein B did not vary significantly, while apoprotein AI was markedly increased (+20 and +20%, respectively). In terms of the serum phospholipid fatty acids, the GLA ingestion was also accompanied by dose-dependent decrease in linoleic acid and increases in all its derivatives. Heterogeneous variations were observed in the n-3 derivatives: the 20:5 n-3 was decreased but the 22:5 n-3 and the 22:6 n-3 remained stable. A decrease was observed for the 18:0 and the 24:0, while the 18:1 n-9 was increased. These results indicate that dietary gamma-linolenic acid is more efficient in reducing serum LDL cholesterol than dietary linoleic acid.
