Food may in various ways give rise to disease. Over-eating is one source of injury to the system. Part of the food is not absorbed, and may become putrid in the intestines, causing dyspepsia, constipation, or diarrhoea. If the excess consumed is principally in the nitrogenous materials, it leads to an increase of the chemical changes in the body, and the person tends to become thin rather than the contrary. It may cause gouty conditions and disease of the kidneys and blood-vessels. Excess of starchy and sugary foods often causes acidity and flatulence and great fattiness of the body, as is also the case with excess of fatty food.
Deficiency of Food produces gradual loss of flesh and weakness of all the bodily organs, particularly of the heart. The body is, moreover, little able to resist cold and various diseases, and thus half-starved people are easily attacked by fevers and consumption.
If food is not given in about the right proportions, various dyspeptic troubles may arise, and the body will not be properly nourished. Similarly, eating food in a hurry, bad cooking of food, and a bad arrangement of meals, the food being taken too often or too seldom, or too much taken at one time and too little at another, will lead to stomach troubles.
One of the best-known diseases caused by the absence of some essential of a diet is called scurvy. This used to be very common on board ships on long voyages, and was caused either by the great use of salt beef, or (much more probably) by the absence of fresh vegetables containing the necessary vegetable acids. Nowadays fresh meat can be more easily taken on long voyages, and potatoes and lime-juice are freely given, so that sea scurvy is practically unknown. In large towns, however, we very frequently see the same disease, as shown by the sore and bleeding gums and the appearance of blood under the skin like small bruises, and the condition is only found in badly-fed people, who will tell you that they live almost entirely on bread and butter and tea, with meat occasionally, and fresh vegetables sometimes on Sunday. This land scurvy soon disappears when proper food is given.
Rickets is a disease found in young children, and is very largely due to feeding with improper food (such as starchy materials,), and to an absence of fresh air. The child perspires chiefly about the head at night, and the whole body seems to be tender and sore, the ends of the bones becoming soft and enlarged, especially near the ankles and wrists, and deformities of the limbs, such as bow legs or knock knees, may result. If there is any sign of this disease beginning, the child must not on any account be allowed to walk for many months, and he should be given plenty of fresh air, sunlight, and good nourishing food.
It is a curious fact which we cannot explain that some food, such as ripe cheese, game, and "high" mutton is only eaten in a state of decomposition, and yet no evil results follow. Apart from these examples, we know that putrid food ought to be absolutely avoided, as it may cause intense poisoning, with vomiting, diarrhoea, great collapse, and even death. Such cases are, unfortunately, not uncommon from the eating of putrid meat pies, hams, and sausages. ,