Saturated fats: The very bad,the not-so-bad and the benign

Common wisdom in the prevention of heart disease has dictated that we reduce saturated fat in our diets and, when possible, substitute polyunsaturated fats and oils. However, little research has been done to distinguish the different types of saturated fats and their relative harmfulness to cardiovascular health. Hu and workers at the Harvard School of Public Health have found that, although some saturated fats are definitely worse than others, food sources are so intermingled that it is a nonproductive exercise to separate "bad" from "benign" saturated fats in everyday diets.

The research was part of the Nurses' Health Study and tracked instances of fatal heart disease and nonfatal myocardial infarction in 98,462 female nurses over a 14-year period. Special consideration was given to the subjects' consumption of the different types of saturated fatty acids: oleic, myristic, lauric, palmitic, stearic and linoleic, which are distinguished by the length of the carbon chain in their respective chemical formulas. Though one fatty acid (myristic, found in coffee creamer, palm oil, hard cheese and full fat dairy products) was found to raise cholesterol levels more than the others, there was little distinction among these fats on their effects on cardiovascular risk. Further, the most harmful saturated fatty acids are often combined with less harmful ones in the same food sources, for example: red meat, whole milk, hard cheese, cream, butter, ice cream or coffee creamer. Significantly reduced risk was only found when saturated fats as an entire category were replaced by foods containing monounsaturated and/or polyunsaturated fats.

An accompanying editorial by William Connor dashes the hopes of chocolate lovers who had recently been encouraged by research suggesting that stearic acid, the primary fat ingredient in chocolate, was heart protective. He concurs with Hu et al.'s conclusion that the best that can be said for stearic acid is that it is benign, simultaneously raising both HDL ("good") and LDL ("bad") cholesterol levels. It is not worthwhile singling out stearic acid as a "safe" form of saturated fat , and chocolate lovers are better off seeking saturated-fat-free alternatives.

Hu FB et al. Dietary saturated fats and their food sources in relation to the risk of coronary heart disease in women. Am J Clin Nutr 1999; 70:1001-8.