Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: March 1, 2003
Publication Date: May 1, 2004
Citation: Heird, W.C. 2004. Fats and fatty acids. In: Kleinman, R.E. editor. Pediatric Nutrition Handbook. 5th Edition. Elk Grove Village. American Academy Press. p. 261-284. Technical Abstract: The absolute fat requirement of the human species is the amount of essential fatty acids needed to maintain optimal fatty acid composition of all tissues and normal eicosanoid synthesis. At most, this requirement is no more than about 5% of an adequate energy intake. However, fat accounts for approximately 50% of the non-protein energy content of both human milk and currently available infant formulas. This is thought to be necessary to insure that total energy intake is adequate to support growth and optimal utilization of dietary protein. In theory, the energy supplied by fat could be supplied by carbohydrate from which all fatty acids except the essential ones can be synthesized but, in practice, it is difficult to assure an adequate energy intake without a fat intake considerably in excess of the requirement for essential fatty acids. In part, this is because the osmolality of such a diet containing simple carbohydrates (e.g., mono and disaccharides) will be sufficiently high to produce diarrhea and such a diet containing more complex carbohydrates may not be fully digestible, particularly during early infancy. Moreover, metabolic efficiency is greater if non-protein energy is provided as a mixture of fat and carbohydrate rather than predominately carbohydrate. This is because approximately 25% of the energy content of carbohydrate that is converted to fatty acids is consumed in the process of lipogenesis. Fat also facilitates the absorption, transport and delivery of fat-soluble vitamins and, in addition, is an important satiety factor. Considering these issues, participants in a recent workshop concluded that the lower limit of fat intake that can be recommended is at least 15% of total energy intake but that a more practical recommendation is in the range of 30% of energy intake. These issues are important in consideration of the age at which a prudent (i.e., lower fat) diet to reduce the risks of cardiovascular disease is recommended.