Calorie conversion factors. An experimental reassessment of the factors used in the calculation of the energy value of human diets

Abstract

I .The intake and excretion of total nitrogen, fat and the various forms of carbohydrate, and the heats of combustion of the diet, urine and faeces were measured in groups of young men, young women, elderly men and elderly women.2. Each group was studied while the subjects were eating two diets in turn, which differed in their contents of unavailable carbohydrate; the young women were also studied on a third diet which was rich in unavailable carbohydrate.3. Increasing the intake of unavailable carbohydrate resulted in a greater faecal loss of energy, and in most instances of nitrogen and fat. 4.There was no significant effect of sex or age on the apparent digestibility of protein, fat or available carbohydrate.5. The results are used to evaluate the use of calorie conversion factors for calculating the metabolizable energy content of mixed diets.6. These show that for practical purposes the classical Atwater factors can be used to calculate the metabolizable energy of a diet with reasonable accuracy, provided that when available carbohydrate (as monosaccharides) values are used in the calculation a factor of 3.75 kcal/g (15.7 kJ/g) is used.7. The studies demonstrate that the accuracy of any method for calculating the metabolizable energy of a diet is largely determined by the accuracy with which the method is capable of predicting the gross energy of the diet.The measurement of the metabolizable energy supplied by a diet is not technically difficult, but in practice such measurements are time-consuming, expensive and, most important of all, they place quite severe restrictions on the activities and mode of life of the person eating the diet. In addition, a knowledge of the metabolizable energy supplied by the dietary intake is often required in situations where its direct measurement is impossible or, at best, highly impracticable. In these situations the only alternative is to use a procedure for calculating the metabolizable energy of a diet from its chemical composition.The various systems of calorie conversion factors provide a method for performing this calculation. All the systems used at present have their origins in work carried out at the end of the last century and the beginning of the present one (Rubner, 1885; Atwater, 1903).Atwater and his colleagues carried out a considerable amount of experimental work with human volunteers, which has been admirably reviewed by Merrill & Watt (1955), but most of the modifications of the 'classical' Atwater factors have been based on https://www.cambridge.org/core/terms. https://doi

Nutrition, ageing and ill health

“…Absorption of some nutrients, in particular vitamin B 12 , may be impaired because of mild ageing-related achlorhyria, but the evidence here is incomplete (Russell, 1986). Southgate & Durnin (1970) found no evidence of impaired absorption between young and elderly subjects when they measured the nutrient composition of food eaten and urine and faeces excreted using chemical analysis. Some researchers have reported widespread nutritional deficiencies associated with bacterial contamination of the small bowel (Roberts et al 1977;McEvoy et al 1983;Haboubi & Montgomery, 1992).…”

Comparison of nutrients in the food composition tables available in the nine European countries participating in EPIC

“…The traditionally applied conversion factors are the so-called` Atwater' factors, that is, 4, 9, 4, 7 kcalag, or 17, 37, 17, 29 kJag (Atwater, 1910) applied to protein, fat, total CHO and energy contents, respectively. Whenever carbohydrates are expressed in monosaccharides, the so-called`Southgate and Durnin' factor of 3.75 kcalag or 16 kJag is used, instead of 4 kcalag or 17 kJag (Southgate & Durnin, 1970 …”

A new look at dietary carbohydrate: chemistry, physiology and health

“…Energy value of dietary carbohydrate Dietary carbohydrates which are absorbed as hexose (glucose, fructose, galactose etc), have a caloric value of 3.75 Kcal/g (15.7 KJ/g) (Southgate & Durin, 1970) and their cellular catabolism produces around 38 mol ATP/mol . However, NDO, resistant starch and NSP, because they are only partly converted to short chain fatty acids through fermentation, are metabolically less ef®cient than hexose, have a lower caloric value, of between 0 Durin, 1970) and2.4 (Goranzon &Forsam, 1987) Kcal/g (0±10 KJ/g) depending both on the degree of their colonic fermentation and the assumptions of the fermentation model used.…”

“…However, NDO, resistant starch and NSP, because they are only partly converted to short chain fatty acids through fermentation, are metabolically less ef®cient than hexose, have a lower caloric value, of between 0 Durin, 1970) and2.4 (Goranzon &Forsam, 1987) Kcal/g (0±10 KJ/g) depending both on the degree of their colonic fermentation and the assumptions of the fermentation model used. Via the catabolism of the absorbed short chain fatty acids, they produce 10±17 mol ATP/mol of fermented -osyl moiety (glucose, fructose, etc) .…”