from "Rust Out" by Dr. Royce Bailey, page 33

In 1990, it was found that when “trans” fats  were substituted for monounsaturated fats (like olive oil) the total cholesterol rose only slightly.  “Trans” fats are artificially manufactured unsaturated fats. Naturally occurring unsaturated bonds are in the “cis” position.  But what’s scary is the bad LDL cholesterol went up and the good HDL cholesterol went down, therefore, increasing substantially the potential for heart disease.  But some critic argued the levels were too high in the original study so the USDA did a similar study with lower levels closer to the American average.  They found even a small amount of “trans” fat in the diet boosted bad LDL by 6% (slightly less than saturated fat did) and dropped good HDL by 3%.  Cardiologists worry about too little heart-protecting HDL and too much clog-causing LDL.  At Harvard, three studies have now found that people who consume more “trans” fats have more heart disease.  Example: Men and women, average age 58, who ate the most “Trans” margarine (more than 2 pats of margarine/day) had a heart attack risk 2 times greater than those who ate the least (less than one pat a day).  

—Remedy  Sept/Oct 1995, p 30