There is a growing body of evidence linking the fats that circulate in the blood with atherosclerosis. There are several types of fats in the blood: the so-called "bad" or low-density cholesterol (LDL-C), the protective or "good" HDL-C, and a butter-like substance called triglycerides. Studies that show that the higher cholesterol level, particularly bad cholesterol, the higher the risk of blood vessel damage. Other studies show that feeding animals with cholesterol leads to atherosclerosis.
Saturated fats, such as lard, butter, and other animal fats, appear to have several adverse effects on cholesterol and the development of blood vessel disease. Some studies show that they may increase the uptake of cholesterol from the intestines into the blood. When such fat becomes part of the blood, fatty particles appear to stick better to blood vessel walls, forming deposits and making the arteries narrower. Also, some saturated fats appear to contribute to the accumulation of LDL-cholesterol in the blood.
What are trans-fatty acids?
Trans-fatty acids are formed when vegetable oils undergo a chemical process during commercial processing, called "hydrogenation," to make fats into solids such as margarine and shortening. Trans-fatty acids behave like saturated fats by increasing LDL-cholesterol in blood. They may also reduce HDL-cholesterol.
On average, 3% of the calories we eat come from trans-fatty acids. Major sources are vegetable shortening, hard margarine, and foods that contain these products, such as commercially prepared baked goods. These foods should be eaten in limited quantities.
Treatment of high levels of blood cholesterol with diet or drugs decreases the chances of angina or heart attack, both in people who do not have evidence of heart disease and in those who have survived a heart attack or heart surgery.