Why we need fats
Nothing else can stimulate the taste buds quite like the smell of fat. The human body comes adapted with a special affinity for this resource, according to evolutionary nutrition researchers S. Boyd Eaton, MD, and Stanley B. Eaton III (a father-son duo) (1998). Dr. Eaton and Eaton suggest early hominids eventually ate a greater amount of nuts and seeds and later, around 2.5 million years ago, humans on a hunter-gatherer diet might have preferred animal fat, specifically supplied in the brain and marrow—an alteration of diet that may have been a factor in supporting a larger brain (1998). This history of fat in the diet helps shape understanding of how vital fat is for the diet.
The body needs fat for various functions as well as other fat-related substances in the family of lipids. Most lipids in the body are of a type called triglycerides—three fatty acids with a glycerol backbone—which act as concentrated sources of energy stored in greater amounts in adipose tissue cells (Tortora & Derrikson, 2006, p. 46). Triglycerides are used as a “back-up” fuel source, as insulation to help maintain body temperature, and as “protective padding for vital organs” (Nix, 2005, pp. 34 & 40). The major lipid that makes up cell membranes is the phospholipid—two fatty acids with a glycerol backbone—along with other fat-related substances cholesterol and lipoproteins (Tortora & Derrikson, 2006, p. 46). Multiple types of lipids also play a role as a protective covering for nerve cells called a myelin sheath, which is also important for increasing speed of nerve impulses (Tortora & Derrikson, 2006, p. 410). To maintain proper amount of lipids in the body, dietary fat is important.
Dietary fat, however, occurs in various ways. The “building blocks” of fats are fatty acids, which can consist of short-, medium- or long-chains of carbon atoms with a methyl group on one end and carboxyl group on the other (Nix, 2005, p. 31). The fatty acids can also be “saturated’ or “unsaturated” (including polyunsaturated) depending on their amount of hydrogen atoms (p. 31). The saturated are generally from animal origin and the unsaturated from plant origin, although there are plants that contain saturated fat and animals will have unsaturated fat (p. 31-33). Essential fatty acids are specifically types of polyunsaturated fats that are necessary for the body (p. 33). Trans fats occur when unsaturated fats are chemically “saturated” to make them more solid at room temperature (p.35). With the various types of fatty acids, confusion may lie in how to best utilize food with proper amounts of each in the diet.
Too much fat is harmful, but so is not enough. When the diet is high in fat over time, higher incidence of chronic diseases (Nix, 2006, p. 39). Heart disease is a good example being the leading killer of men and women in the U.S.A. According to the American Heart Association (AHA), great amounts of fat, especially of saturated fat and trans fat, contribute to obesity and heart disease (2008). A low-fat diet, then can help protect the heart. However, when the body does not take in sufficient fat, however, essential fatty acid deficiency can occur (Nix, 2006, p. 39). Essential fatty acid deficiency is rare, but signs include scaly dermatitis, alopecia, thrombocytopenia and growth retardation (Morley, 2007). The key to the health is a correct balance.
Fat intake in the right amounts as well as the right kinds leads to a healthy lifestyle. U.S. Dietary Guidelines recommend no more than 20% to 35% of total fat, no more than 10% calories from saturated fat, and no more than 300 mg/day of dietary cholesterol (Nix, 39, 2006). AHA adds that it is best to avoid saturated and trans fats, replacing them with mono- and polyunsaturated fats “while still limiting” total fat (2008). Of the polyunsaturated, it’s important to remember that two are essential—omega-6 and omega-3 fatty acids.
Omega-3 is the more important of the two. In 2002 AHA began recommending people without heart disease consume fish at least twice a week to help maintain a health heart as long as a close watch was instituted over intake of fish contaminants (e.g. mercury) (Kris-Etherton et al). Further, AHA recommends those with heart disease take at least 1 g per day of EPA/DHA omega-3 fatty acids in capsule form (to avoid contaminants of eating fish), and for 2 to 4 grams daily in capsule form for those who needed to lower triglycerides (Kris-Etherton et al). In addition, the U.S. Food and Drug Administration (FDA) put out a qualified claim about “reduced risk of coronary artery disease” for any whole food, packaged food or dietary supplement that contained both EPA/DHA omega-3 fatty acids (2004). The information suggests that a low-fat diet with an emphasis on polyunsaturated oils especially omega-3 fatty acids is best for health. Since the brain is made up of mostly omega-3 fats, that would explain why hunter-gatherers preferred the brain on the menu.
American Heart Association. (2008, Sept 21). Face the Fats. Retrieved Sept. 17, 2008 from http://www.americanheart.org/presenter.jhtml?identifier=3046074.
Department of Health and Human Services Centers for Disease Control and Prevention. (2008). Heart Disease. Retrieved Sept. 17, 2008 from http://www.cdc.gov/heartdisease/.
Eaton, S.B. & Eaton, S.B. III, (1998). Evolution, diet and health. [Scientific Session – International Congress of Anthropological and Ethnological Sciences in Williamsburg, VA]. Retrieved Sept. 17, 2008 from http://www.cast.uark.edu/local/icaes/conferences/wburg/posters/sboydeaton/eaton.htm.
Kris-Etherton, P.M., Harris, W.S., & Appel, L.J. (2002). Fish consumption, fish oil, omega-3 fatty acids and cardiovascular disease. Circulation: Journal of the American Heart Association, 106; 2747-2757. Retrieved Sept. 22 from http://circ.ahajournals.org/cgi/reprint/106/21/2747.
Morley, J.E. (2007, June). Essential Fatty Acid Deficiency. The Merck Manual for Healthcare Professionals. Retrieved Sept. 21 from http://www.merck.com/mmpe/sec01/ch002/ch002d.html.
Nix, S. (2005). Williams’ Basic Nutrition & Diet Therapy, 12th ed. St. Louis, MO: Elsevier Mosby.
Tortora, G.J., & Derrikson, B. (2006). Principles of Anatomy and Physiology, 11th ed. New York: John Wiley & Sons.
U.S. Food and Drug Association (2004). FDA announces qualified health claims for omega-3 fatty acids. Retrieved on Sept. 21, 2008 from http://www.fda.gov/bbs/topics/news/2004/NEW01115.html