When eaten in excess, sugar may temporarily appear in the urine unaltered.
It might be inferred that, as all starch must be converted to sugar before it can be used by the body, starches might be discarded and replaced by sugars. A small quantity of sugar, however, soon surfeits the appetite, and if the foods were confined to those having a surplus of sugars, sufficient food would not be eaten to supply other needs of the body. This lack of appetite occasioned by an excess of sugar is due, partly, to the fact that the gastric juice is not secreted so freely when there is much sugar in the stomach.
Because of the slower secretion of gastric juice and the surfeit of the appetite occasioned by them, sweetened foods should not be used at the beginning of a meal, and, while a moderate amount of sugar is desirable, a surfeit will cause indigestion. This is particularly liable when one eats sufficient starch and sugar at a meal and then eats candy between meals.
Sugar is so readily oxidized and supplies heat and energy so promptly, that the fats stored in the tissues are not called on until the latent energy in the sugar is used. The power of sugar to fatten thus lies in sparing the use of body fat; when starch and fat are used in addition to sugar an excess of fat quickly results. Therefore, those who wish to reduce in flesh should eat sparingly of sugar that the starches and fats may be used to furnish energy, but sugar should be as freely used as the system can handle it, by those who wish to build up in flesh.
Broadly speaking, about one-fourth of a pound of sugar, daily, in connection with other foods, is well utilized by the system, the quantity depending on whether one leads an active or a sedentary life.
The natural flavor of fruits and grains is very largely destroyed by sugar, which is used too freely on many articles of diet. Sugar should never be added to fruits while cooking, if intended for immediate use, as the acids of the fruits neutralize a portion of the sugar. More sugar is thus used than is needed after the cooking process is completed.
The sweet taste in all fruits and vegetables is due to the presence of sugar. Sweet potatoes, beets, carrots, parsnips, turnips, grapes, figs, and dates are especially rich in sugar, and when these are furnished with a meal, in any appreciable quantity, the starches should be restricted—notably bread, Irish potatoes, and rice.
Those who do hard work in the open air, because of the increased oxidation, can consume larger quantities of sugar in pie or other pastry, which ordinarily would be difficult to digest. One who lives an indoor life should refrain from an undue indulgence in such foods.
For one who is undernourished, sugar is a desirable food, if the starch be diminished in proportion as the amount of sugar is increased; but the tendency in sweetening foods is to take more starch also than the system requires, since it is the carbohydrate foods which are ordinarily sweetened—not the proteins.
On account of their latent heat and energy, sugars are more desirable in cold weather than in warm. For this reason Nature supplies them more abundantly in the root vegetables, eaten more freely in cold weather. More puddings and heavier desserts may be eaten in cold weather.