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     At present it will be sufficient to point out that abundant experimental evi-
dence has accumulated to show that the nutritive values of the fats and carbo-
hydrates of food are almost proportional to the amount of energy that they can fur-
nish; consequently it is only important that the quantity of either or both be
such that their total energy, when added to that of the protein of the diet, shall
supply the amount required by the body. The maximum amount of energy that
can be obtained by the body is not the total potential energy of the food con-
sumed, since the potential energy of the corresponding fæces must be deducted.
Furthermore, the body is not capable of completely oxidising the absorbed protein,
the incompletely oxidised products being excreted in. the urine, and the energy
eliminated in this way must also be deducted. The net or actual energy-value to
the body is the total potential energy of the food minus that of the corresponding
fæces and urine.* In dealing, however, with the vegetarian dietaries in force in
Indian jails another factor has to be considered with regard to the energy or fuel
value of a diet; this factor is the excessive fermentative processes in the digestive
tract. Anyone who has experience of the effects of excessive carbohydrates in the
diet will readily recognise the clinical features of excessive intestinal fermentation
in the noisy eructations, flatulency, tendency to diarrhœa and colic and, above
all, the changes in the appearance and character of the fæces—soft from admixture
with gas, and light brown to yellow in colour for the same reason—exhibited,
sometimes in a marked degree, by the prisoners examined by us.

     This excessive fermentation of carbohydrates constitutes an important
source of loss of potential energy of the diet, through the conversion of sugar or
starch into carbon dioxide and fermentative products of low caloric value, such
as acetic acid, lactic acid, etc.

     This loss, which may be large in amount depending on the degree of fermenta-
tion present, will reduce the fuel value of the diet very considerably, and may
afford a likely explanation of the remarkable want of body fat in many of
the ordinary working population of Bengal. The loss of fuel from fermenta-
tion being so considerable that, although the diet is exceedingly rich in carbo-
hydrate material, none or only a minimum can be stored and even in some cases
where under-nutrition is well-marked, the body tissues are drawn on to meet the
caloric requirements. This method of waste due to excessive carbohydrates in
the jail dietaries of Bengal is, we believe, a most important factor and one that
must be taken into consideration not only in calculating the fuel value of the diets
but also in connection with the intestinal troubles that are so prevalent in Bengal
jails and indeed amongst the people generally.

     So far as we know there is no method by which this loss can be even approxi-
mately computed; but that it is an important factor in reducing the fuel value of

* The narrative requirements of the body. Benedict, American Journal of Physiology, Vol. XVI, No. IV.

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