Stearic Acid : Does It Raise Blood Cholesterol Like a Saturated Fat?

Partially hydrogenated vegetable oils, the primary source of trans fatty acids, provide a stable medium for frying applications and a solid, functional fat for spread and baking applications. The reformulation of food products to remove trans fatty acids is a major issue facing food and restaurant industries. Reformulation of spread and baking applications has been more challenging due to the need for specific physical/ functional properties in a fat which is imparted by saturated and/or trans fatty acids. As a result, interest has been refocused on saturated fatty acids.

Saturated fat in the U.S. food supply is primarily composed of three saturated fatty acids: myristic, palmitic and stearic acids. From a structural standpoint, these fatty acids differ only in their size (a.k.a.fatty acid chain length). This structural difference can play a role in the functionality of a solid fat. Major sources of these fatty acids are animal fats, tropical fats/oils and fully hydrogenated vegetable oils. Animal fats predominantly contain palmitic and stearic acids; tropical fats/oils predominantly contain palmitic, myristic, lauric or stearic acids (depending on the plant source); and fully hydrogenated vegetable oils contain predominantly stearic and palmitic acids.

Governmental agencies and nongovernmental organizations have evaluated data on the serum cholesterol effects of these fatty acids. Consistently, myristic and palmitic are viewed to raise serum cholesterol levels while stearic is viewed as being neutral on serum cholesterol levels.^1-3 Stearic acid has been observed in some, but not all studies, to increase a specific factor related to blood clotting at intake levels very much greater than its level in the typical U.S. diet.^4-9 In the current context of replacing trans fatty acids, stearic acid has received attention both for its impact on serum cholesterol neutrality and blood clotting. The blood clotting issue has been commented upon by the 2005 U.S. Dietary Guidelines Advisory Committee. Based on their review of the scientific data, their report states “Thus, at intakes of stearic acid that are equal to or slightly higher than amounts consumed in the United States, no adverse effects on fibrinogen levels would be expected.”

1) Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients), Chapters 8 and 11, Institute of Medicine, National Academy Press, Washington, D.C. (2002).
2) Diet, Nutrition and the Prevention of Chronic Diseases, Joint WHO/FAO Expert Consultation, World Health Organization, Geneva. WHO Technical Report Series 916, p. 147 (2003) [available at http://www.fao.org/DOCREP/005/AC911E/AC911E00.HTM].
3) Circulation 103:1034-1039 (2001).
4) Thrombosis & Haemostasis 73:239-42 (1995).
5) Thrombosis & Haemostasis 77: 99-104 (1997).
6) Journal of Nutrional Biochemistry11:408-16 (2000).
7) European Journal of Clinical Nutrition 55:88-96 (2001).
8) American Journal of Clinical Nutrition 79:696-73 (2004).
9) Journal of Nutrition 135:2805-11 (2005).
10) 2005 Dietary Guidelines Advisory Committee Final Report - Fats, Section D4, U.S. Department of Health and Human Services, Washington, D.C. (2004), pp. 12-13 [available at http://www.health.gov/DietaryGuidelines/dga2005/report/PDF/D4_Fats.pdf].