Effect of dietary elaidic versus vaccenic acid on blood and liver lipids in the hamster

Male hamsters (30 per group) were fed five different semi-purified diets ad libitum. The diets, containing 30% of energy (en%) as fat, differed in the ir dietary fat composition (specified fatty acids exchanged at 10 en%) and were fed for 4 weeks. The five fatty acids compared in mixed triglycerides were elaidic acid (C18:1 9t), vaccenic acid (C18:1 lit), their tis-counterp art oleic acid (C18:1 9t), medium-chain fatty acids (MCFA: C8:0 and C10:0), and palmitic acid (C16:0). Compared with oleic acid, dietary MCFA and palm itic acid tended to increase blood cholesterol levels in the hamsters. The effect of elaidic and vaccenic acid on blood cholesterol did not differ fro m that of oleic acid. When elaidic acid and vaccenic acids were compared di rectly, the ratio of LDL/HDL-cholesterol in plasma was significantly higher in hamsters fed vaccenic acid than in those fed elaidic acid, and elaidic acid was incorporated at low levels, but more efficiently than vaccenic aci d at the sn-2 position of platelet phospholipids. Biological consequences o f this low incorporation are considered unlikely as levels of arachidonic a cid (C20:4 n-6) and docosohexaenoic acid (C22:6 n-3) in the platelet phosph olipids of all dietary groups did not differ. With respect to the effect on the LDL/HDL-cholesterol ratio, elaidic acid may be preferable to vaccenic acid. We conclude that this animal study does not provide evidence for the suggestion, based on epidemiological observations, that elaidic acid would be more detrimental to cardiovascular risk than vaccenic acid. (C) 2001 Els evier Science Ireland Ltd. All rights reserved.