Trans Fats Increase Small Dense LDLs

The evidence continues to mount that the trans fatty acids produced when vegetable oils are partially hydrogenated are the most dangerous fats in the American diet. It is now well established that these trans fatty acids raise LDL levels in the body nearly as much as do saturated fatty acids. Elevated LDL has been shown to be the single best predictor of the growth of atherosclerotic plaques over a prolonged time period. It is also well established that trans fatty acids lower the “good,” or HDL, cholesterol as well. HDL is involved in removing cholesterol deposited in the artery wall and low HDL levels are also clearly associated with an increased risk of coronary heart disease. Research has also shown that small dense LDL particles are more atherogenic than are larger LDL particles. However, there has been little research regarding the impact of trans fatty acids on LDL particle size.

A recent double-blind, randomized clinical trial of 36 older (57-73 years) men and women sought to compare the impact of partially hydrogenated oil with varying amounts of trans fatty acids to butter (rich in saturated fat) on LDL particle size. All food was prepared for the subjects and served to them for 35 days. Blood lipids were checked on the 35th day. As expected, total and LDL levels were higher when the subjects consumed butter than when they consumed even the most hydrogenated vegetable oil. However, HDL levels tended to be lower when the subjects were given the hydrogenated oils than when they consumed the butter. In addition, serum triglyceride levels also trended higher with increasing trans fatty acid content of the diet. Lower HDLs and higher triglycerides are associated with increased cardiovascular disease. Finally the average LDL particle size also shrank with increasing hydrogenation of the vegetable oil. These data demonstrate yet another reason trans fatty acids should be minimized in the diet.1Bottom Line: Foods like doughnuts, fried chicken, cakes, cookies, chips and French fries as well as stick margarine and vegetable shortenings can contain dangerously high levels of trans fatty acids. Those at risk for CVD should avoid such foods.By James J. Kenney, PhD, RD, FACN.1. Am J Clin Nutr 2003;78:370-5.