Energy Metabolism in Man

In formulation of diets to meet energy requirements, proteins and carbohydrates are considered to yield 4 cal. per gram, and fats, 9 cal. per gram. The specific dynamic action of foodstuffs must also be considered and is usually calculated as 6 % of the total caloric value of the food over a 24-hr. period.2  

In spite of the difficulties in determining exact caloric requirements, 

DuBois and W. H. Chambers, Calories in Medical Practice, in Handbook of Nutrition, A Symposium, American Medical Association, Chicago, 1943, pp. 55ff. 

Caloric requirements in disease have also been the subject of study. There is an increase in basal metabolism of about 13% for each degree (centigrade) rise in body temperature. Accordingly, all febrile illnesses increase energy needs. Basal metabolism is increased in hyperthyroidism and is often elevated in other endocrinopathies, in certain blood dyscrasias and in heart or lung diseases accompanied by severe dypsnea. Caloric undernutrition is common in these conditions which are associated with an increased energy requirement. It is also frequently encountered in illnesses in which anorexia is a prominent finding and in conditions in which calories are lost in the stool or urine, such as diarrheal diseases or diabetes mellitus, 

Recommended Dietary Allowances, National Research Council, Food and Nutrition Board, Reprint and Circular Series No. 129, Washington, 1948. Canadian Bulletin on Nutrition, Council on Nutrition, Ottawa, Vol. 2, No. 1, 1950. 

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Reeds PJ, Fuller MF, Nicholson BA (1985) Metabolic basis of energy expenditure with particular reference to protein. In Garrow JS, Halliday D (eds) Substrate and energy metabolism in man. Libbey, London... 

Blaxter, K. (1989). Energy Metabolism in Animals and Man. Cambridge Cambridge University Press. 

Spencer H, Kramer L, Norris C, et al. 1972a. Certain aspects of radiostrontium metabolism in man. In International Conference on Strontium Metabolism, ed. Second international conference on strontium metabolism, Glasgow and Strontian, 16-19 August, 1972. TID 4500 59th ed. Health and Safety Laboratory / U.S. Atomic Energy Commission, 335-346. 

Sahlin, K., Intracellular pH and energy metabolism in skeletal muscle of man with special reference to exercise, Acta Physiol Scand. Suppl, 455, 1,1978. 

K. Blaxter, Energy metabolism in animals and man, Cambridge University Press, Cambridge, 1989, p. 336. 

Spencer, H. and Rosoff, B. (1963). Metabolism and removal of rare earths in man, page 171 in Diagnosis and Treatment of Radioactive Poisoning, IAEA Publication No. STI/PUB/65 (International Atomic Energy Agency, Vienna). 

GH administered to hypophysectomized rats in vivo causes a drop in the level of plasma non-esterified fatty acids (NEFA), followed by a prolonged increase in this level [89]. This appears to be due to increased utilization of lipids - increased uptake of NEFA by muscle preceding increased output by adipose tissue. As a consequence GH diverts the energy metabolism of the organism from carbohydrate utilization to lipid utilization, and acts to oppose the effects of insulin. Actions of GH on lipid metabolism are particularly marked in man, where GH levels become elevated on fasting and presumably serve to help stimulate the increased lipid utilization seen in this condition. In contrast, in the rat, GH levels fall on fasting. 

The supply of Man to sensitive species also leads to decreases in phospho compounds such as ATP, polyphosphate, Glc 6-P and phosphoenolpyruvate, significant high-energy intermediates in further metabolism. The decreases of these are more pronounced than those of... 

Uric acid that is produced in man is essentially the product of the action of the enzyme xanthine oxidase on xanthine and hypoxanthine. A tiny amount of uric acid may be ingested as part of the diet, but the great bulk is the result of the action of this enzyme on these two purines. These purines are themselves produced either as a result of the breakdown of cellular material in toto, the turnover of nucleic acids in the cells, or as a result of the intermediary metabolism of various purine nucleotide derivatives. These latter compounds are active in the flow of energy, in methyl group transfer reactions, and as part of the functional molecule of many vitamins. There is direct and indirect evidence that some of the uric acid derives from all these sources. Essentially this evidence consists of the demonstration that other parts of the nucleie acids are found in the urine, such as pyrimidine breakdown products (P9) and methylated purines, which are found only in nucleic acids. There is also isotopic evidence that some labeled purines appear in the urine too quickly after administration of radioactive precursors... 

Coward, W. A., Prentice, A. M., Murgatroyd, P. R., Davies, H. L., Cole, T. J., Sawyer, M., Goldberg, G. R., Halliday, D., and Macnamara, J. P. (1984). Measurement of COj and water production rates in man using H, -labelled H2O comparison between calorimeter and isotope values. In Human Energy Metabolism Physical Activity and Energy Expenditure Measurements in Epidemiological Researdi Based Upon Direct and Indirect Calorimetry (A. J. H. van Es, ed.), pp. 126-128. EURO-NUT, The Netherlands. 

Most of the galactose and mannose produced in the endosperm of all these legumes is absorbed by the cotyledons and further metabolized. Several workers have proposed that these sugars are rapidly phosphorylated (to Gal-l-P and Man-6-P). If not directly used for energy metabolism they might be transformed to sucrose and even to starch (this accumulates in fenugreek cotyledons) which... 

In industry, manganese is a metallic element used chiefly as an alloy in steel to give it toughness. In nutrition, it is an essential element for many animal species. Manganese is an activator of several enzyme systems involved in protein and energy metabolism and in the formation of mucopolysaccharides. The human body contains 12 to 20 mg of manganese. So, an essential function of the element must be assumed to exist in man. 

Some researchers have suggested that combined deficiencies of selenium and vitamin E might contribute to heart disease in man because these nutrients help maintain adequate levels of coenzyme Q in the heart muscle. (Coenzyme Q is a vital cofactor in energy metabolism.) If this cofactor is lacking, the production of energy in the heart and in other muscles may fall off to the extent that these tissues can no longer carry their workloads. This hypothesis is supported by the finding that biopsy samples from the hearts of people with heart disease had subnormal levels of coenzyme Q. Hence, it is noteworthy that the administration of selenium to farm animals raised the levels of coenzyme Q in their hearts. 

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