from the hydrolysis of fats, as well as from the syn-
thesis of acetyl CoA through the oxidation of fats,
glucose, and some amino acids. Lipogenesis from ace-
tyl CoA also occurs in steps of two carbon atoms.
NADPH produced by the pentose-phosphate shunt
is required for this process. Phospholipids form the
interior and exterior cell membranes and are essential
for cell regulatory signals.Cholesterol MetabolismCholesterol is either obtained from the diet or
synthesized in a variety of tissues, including the liver,
adrenal cortex, skin, intestine, testes, and aorta. High
dietary cholesterolsuppresses synthesis in the liver
but not in other tissues.
Carbohydrate is converted to triglyceride utilizing
glycerol phosphate and acetyl CoA obtained from
glycolysis. Ketogenic amino acids, which are metabo-
lized to acetyl CoA, may be used for synthesis of
triglycerides. The fatty acids cannot fully prevent
protein breakdown, because only the glycerol portion
of the triglycerides can contribute to gluconeogenesis.
Glycerol is only 5% of the triglyceride carbon.
Most of the major tissues (e.g., muscle, liver, kidney)
are able to convert glucose, fatty acids, and amino acids
to acetyl-CoA. However, brain and nervous tissue—in
the fed state and in the early stages of starvation—depend
almost exclusively on glucose. Not all tissues obtain the
major part of their ATP requirements from the Krebs
cycle. Red blood cells, tissues of the eye, and the kidney
medulla gain most of their energy from the anaerobic
conversion of glucose to lactate.Resources
BOOKS
Bland, Jeffrey S.; Costarella, L.; Levin, B.; Liska, DeAnn;
Lukaczer, D.; Schiltz, B.; and Schmidt, M. A. (1999).
Clinical Nutrition: A Functional Approach. Gig Harbor,
WA: Institute of Functional Medicine.
Linder, Maria (1991).Nutritional Biochemistry and Metab-
olism, with Clinical Applications, 2nd edition. New
York: Elsevier.
Newsholme E. A., and Leech, A. R. (1994).Biochemistry for
the Medical Sciences. New York: Wiley.
Salway, J. G. 1999.Metabolism at a Glance, 2nd edition.
Malden, MA: Blackwell Science.
Shils, M. E.; Olson, J. A.; Shike, M.; and Ross C. A.; eds.
(1999).Modern Nutrition in Health and Disease, 9th
edition. Baltimore, MD: Wilkins & Wilkins.
Wardlaw, Gordon M., and Kessel Margaret (2002).
Perspectives in Nutrition, 5th edition. Boston:
McGraw-Hill.Williams, M. H. (1999).Nutrition for Health, Fitness, and
Sport, 6th edition. Boston: McGraw-Hill.
Yeung, D. L., ed. (1995).Heinz Handbook of Nutrition, 8th
edition. Pittsburgh, PA: Heinz Corporate Research
Center.
Ziegler, Ekhard E., and Filer, L. J. (1996).Present Knowl-
edge in Nutrition, 7th edition. Washington, DC: Inter-
national Life Sciences Institute Press.
Zubay, Geoffrey L.; Parson, William W.; and Vance, Dennis
E. (1995).Principles of Biochemistry. Dubuque, IA:
William C. Brown.Gita PatelMexican dietseeCentral American and
Mexican diet
Micronesian dietseePacific Islander diet
Middle Eastern dietseeGreek and Middle
Eastern dietMinerals
Definition
Minerals are inorganic elements that originate in
the earth and cannot be made in the body. They play
important roles in various bodily functions and are
necessary to sustain life and maintain optimal health,
and thus are essential nutrients. Most of the minerals
in the human diet come directly from plants and
water, or indirectly from animal foods. However, the
mineral content of water and plant foods varies geo-
graphically because of variations in the mineral con-
tent of soil from region to region.Description
The amount of minerals present in the body, and
their metabolic roles, varies considerably. Minerals
provide structure to bones and teeth and participate
in energy production, the building ofprotein, blood
formation, and several other metabolic processes.
Minerals are categorized into major and trace miner-
als, depending on the amount needed per day. Major
minerals are those that are required in the amounts of
100 mg (milligrams) or more, while trace minerals are
required in amounts less than 100 mg per day. The
termsmajorandtrace, however, do not reflect the
importance of a mineral in maintaining health, as a
deficiency of either can be harmful.
Some body processes require several minerals to
work together. For example,calcium,magnesium,Minerals