John Goodfellow has shown that of very coarse wholemeal bread quite 14 per
cent. was undigested, whilst bread made from ordinary grade wholemeal
showed 12.5 per cent. Such a method of analysis was adopted as it was
believed would exclude other than the food waste. The experiments were
made on a person who was eating nothing but the bread. It seems probable
that a smaller proportion would have remained unassimilated had the bread
not formed the sole food. It is advisable that wheatmeal he ground as
finely as possible, the coarse is not only to a less extent assimilated
but apt to irritate the bowels. Notwithstanding that fine white bread gave
only 4.2 per cent. and a coarse white bread 4.9 per cent. of waste, a fine
wheatmeal bread is more economical as the same quantity of wheat produces
a greater weight of flour richer in proteid and mineral matter. From a
large number of experiments with man, it has been calculated that of
proteids there is digested when animal food is eaten 98 per cent., from
cereals and sugars 8 per cent., from vegetables and fruits 80 per cent.
The difference between the proportions digested of the other food
constituents was much less. Although there is here a theoretical advantage
in favour of animal food, there are other considerations of far more
importance than a little undigestible waste. The main question is one of
health. In some dietary experiments of a girl aged 7, living upon a fruit
diet, of whom we have given some particulars elsewhere, Professor Jaffa
gives the following particulars. During the ten days trial the percentages
absorbed were proteids 82.5, fat 86.9, nitrogen free extract 96, crude
fibre 80, ash 5.7, heat of combustion in calories 86.7. He says,
"generally speaking, the food was quite thoroughly assimilated, the
coefficients of digestibility being about the same as are found in an
ordinary mixed diet. It is interesting to note that 80 per cent. of the
crude fibre appeared to be digested. The results of a number of foreign
experiments on the digestibility of crude fibre by man are from 30 to 91.4
per cent., the former value being from mixed wheat and rye, and the latter
in a diet made of rice, vegetables and meat."
TABLE OF ANALYSIS OF FOOD
Key:
P = Proteins.
Cb = Carbohydrates.
C = Cellulose.
R = Refuse.
W = Water.
Ca = Calories.
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