Submitted to: The American Journal of Clinical Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/9/1998
Publication Date: N/A
Interpretive Summary: Highly unsaturated liquid vegetable oils are used in the manufacture of foods such as margarines, frying oils, and shortenings where melting points and other physical properties similar to saturated fats are desired. A hardening process called hydrogenation is used to convert unsaturated chemical bonds to saturated chemical bonds. For most food usage, partial hydrogenation of the unsaturated bonds in the fatty acids that make up the oil, is adequate. However, during partial hydrogenation, some unsaturated bonds remain unsaturated but undergo chemical change or spacial rearrangement around the bond producing a configuration referred to as "trans" unsaturation. This contrasts to the cis configuration in the natural state of the oil. Over the past 7 years, considerable evidence has accumulated that trans fatty acids are cholesterol raising to a degree similar to that of saturated fatty acids, and may therefore increase the risk of cardiovascular disease. Alternatives to the use of partially hydrogenated vegetable oils as hardening agents in margarines are needed. In this investigation, we demonstrated that margarines hardened by addition of completely hydrogenated vegetable oil, i.e., with no fatty acids in the trans configuration, are more effective in lowering blood lipids than are those made with even small amounts of partially hydrogenated fats (low levels of trans fatty acids). Both types of margarines, however, were better than butter, which contains more saturated fatty acids, with regard to effects on plasma lipids. This information is of interest to edible oil producers, manufacturers of foods containing vegetable oils, and to nutritionists and health professionals interested in dietary strategies for reducing blood cholesterol.
Technical Abstract: In a controlled diet study with 46 adult subjects (23 men and 23 women) blood lipid and lipoprotein modifying effects of butter versus two types of margarine were compared. Each table spread, added to a common basal diet, provided 8.3 energy percent (en%) fat from the spread. Including the spread, diets averaged 34.6 en% fat and 15.5 en% protein and each diet was fed for 5 weeks in a 3X3 Latin square design. One margarine (TFA-M), prepared with partially hydrogenated vegetable oil, was formulated to approximate the average trans monoene content of all forms of trans-contain other margarine (PUFA-M) was free of trans unsaturated fatty acids and contained approximately twice the polyunsaturated fatty acid content of TFA-M (49% versus 27% total PUFA, dry weight). The margarines had similar physical properties at ambient temperature. Fasting blood lipids and lipoproteins were determined on two samples taken from the subjects on different days during the 5th week of each dietary treatment. Compared to butter, total cholesterol was 3.5% lower (p=0.008) after consumption of TFA-M and 5.4% (p<0.001) lower after consumption of PUFA-M. Similarly, LDL-cholesterol was 4.7% lower (p=0.005) and 6.7% lower (p<0.001) after consumption of TFA-M and PUFA-M, respectively. There was no effect for either of the margarines versus butter on HDL-cholesterol or triglycerides. Thus, consumption of either TFA-M or PUFA-M improved blood lipid profiles associated with cardiovascular risk when compared to butter, with a greater improvement with PUFA-M relative to TFA-M.