Fatty Acids
Part 1

How fat consumption can influence the course of HD

Saturated vs. Unsaturated Fat

The whole of issue of fat in the diet has become very confusing, mainly because there are so many different types of fat. Essentially, there are two broad categories of fat: saturated fat and unsaturated fat. These two types of fat differ in their chemical structure. Saturated fatty acids (the building blocks of saturated fat) have no double bonds (a particular kind of chemical link between adjoining molecules) and this lack of double bonds means that there are no gaps in the fatty acid chain: it is packed with CH₂ molecules. Unsaturated fatty acids (the building blocks of unsaturated fat), on the other hand, have double bonds and these double bonds break up the string of CH₂´s and create gaps within the fatty acid chain. See figure 1 for a depiction of the difference between saturated and unsaturated fatty acids. We will explore how this difference in chemical structure affects how different types of fat interact with the body below.

Saturated fats (meats, butter, dairy products) are solid at room temperature, whereas unsaturated fats (vegetable oils) are liquid at room temperature. Due to their difference in chemical structure, saturated fats and unsaturated fats exert different effects within the body. Because saturated fatty acid chains have no gaps, they are able to pack together very tightly. When these tightly packed saturated fatty acids enter the bloodstream, they increase levels of "bad" cholesterol known as low-density lipoprotein (LDL) cholesterol and clog arteries. In comparison, unsaturated fats do not increase "bad" cholesterol and, in fact, are able to increase levels of "good" cholesterol known as high-density lipoprotein (HDL) cholesterol. HDL is able to grab LDL and escort it to the liver where it is broken down and eventually removed from the body. Thus, by increasing levels of HDL, unsaturated fats are able to protect against the damage done by saturated fats. Since heart disease is a leading cause of death for people with HD, it is especially important to keep the heart healthy and limit intake of saturated fat. (For more information on the many complications of HD, including heart disease, click here.) And as we will see below, there are even more reasons than heart disease for people with HD to be conscientious about the types of fat that they consume.

Last Modified: 04/12/2007

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