Much of chocolate’s smoothness comes from cocoa butter, which is the naturally occurring fat in chocolate. Milk chocolate will also contain a small amount of fat from milk ingredients.
Cocoa butter is not a dairy product; it is pressed out of the cocoa bean itself. (See what cocoa butter is, then see how it’s made.) Cocoa butter contains a mixture of saturated and monounsaturated fats.
Stearic acid is the primary saturated fat in cocoa butter, accounting for about one-third of cocoa butter's total fat and more than half of its saturated fat. The remaining saturated fat is primarily palmitic acid. Oleic acid is the primary monounsaturated fat in cocoa butter.
Stearic acid does not raise LDL cholesterol levels like other saturated fats and trans fats do. For this reason, the 2010 Dietary Guidelines Advisory Committee Report recommends that stearic acid not be categorized with known “cholesterol-raising” fats, including other saturated fats and trans fats. Because of cocoa butter’s rich stearic acid content, more than half of the saturated fat in chocolate does not raise blood cholesterol levels.
A recent review of epidemiologic and clinical studies looked at what happened to blood LDL cholesterol when stearic acid was substituted for other types of fats, including trans fats. Results indicate that compared to other saturated fats, stearic acid lowered LDL cholesterol levels, was neutral with respect to HDL cholesterol, and lowered the ratio of total-to-HDL cholesterol.
The review also concluded that replacing trans fats with stearic acid, compared to other saturated fats in foods that require solid fats, showed a decrease or no effect on LDL cholesterol levels.
For more on chocolate and stearic acid, see Taking Chocolate to Heart: For Pleasure and Health from the National Confectioners Association.
As with many things, moderation is key. Yet these studies suggest that modest consumption of chocolate, when balanced with total calories and fat eaten, can be part of a healthy diet.