Sources Of Fat In The Diet

The chief sources of fat in the diet are milk (yielding cream and butter), olive oil, meat fats (especially lard, bacon and salt pork, beef suet and drippings), and oily nuts.

Cheap Forms Of Fat

Butter, cream, olive oil, lard, etc., are all subject to adulteration with cheaper fats, but aside from the fraud in charging a high price there is a legitimate industry for making cheaper products representing these articles. Thus skim milk has its lost cream restored by a homogenized meat fat containing some butter. A substitute for butter is produced from animal fats and sold under special names, etc. The industry is yet in its infancy, although half a century old. The more expensive fats are prized for their flavor, but the cheaper fats carefully refined have also a high nutritive value.

Function

Fats are burned up in the body and produce energy in the form of work or heat. According to Dr. W. Gilman Thompson, the chief uses of fats are as follows:

1. To furnish energy for the development of heat.

2. To supply force.

3. To serve as covering and protection in the body.

4. To make more plastic various structures of the body and give rotundity to the form.

5. To spare the tissues from disintegration; for, although their combustion in the body results largely in the production of heat, they also take to some extent in tissue formation.

6. To serve for storage of energy.

Source Of Body Fat

Twenty per cent. of the normal weight of man is fat. It is derived mainly from fatty foods and carbohydrates. Proteins are transformed into fat only to a very limited degree. It is most readily produced from carbohydrates, or a mixture of carbohydrates and fats.

Principles Of Cooking

Fats are more digestible cold than hot, because hot fat tends to coat and intimately penetrate the food with which it is cooked or eaten, and as this coating is not dissolved by the digestive juices of the mouth or stomach, little or no digestion of carbohydrate and protein can take place in either of these places under such circumstances. Heating fat to a high temperature also changes its chemical nature, often producing irritating substances which interfere with digestion. For such reasons fried food should never be given to invalids.

Digestibility

The majority of fats are not very easily digested, consequently are not tolerated by those suffering from indigestion or by patients acutely ill-; their use should be limited to finely divided forms, as in milk or yolk of egg; it is sometimes even necessary to reduce the fat in milk by skimming off the cream, or to limit the amount of yolk of egg, inasmuch as 30 per cent. of the yolk is fat. Other forms of fat valuable in the invalid's dietary are butter, cod-liver oil, and fat bacon cooked crisp. All fats, except limited quantities of butter and cream, should be forbidden in acute diseases of the stomach, intestines and liver, and in most of the chronic affections. Their uses should be limited also in the presence of gall stones.

Fatty foods should be prescribed for children with rickets and for all who have diabetes. In the latter disease they partly replace the carbohydrates which cannot be used. Fat may be prescribed with benefit in chronic wasting disease, such as tuberculosis, and during convalescence from severe acute disease. The most agreeable and digestible forms should be given. At first a small portion only should be taken, and the quantity increased in proportion to a patient's willingness to accept it. In a general way fats and oils are laxative; consequently useful in case of constipation and equally harmful where there is a tendency to diarrhoea.

Comparative Value Of Fat And Carbohydrates As Fuel Foods

Fats and carbohydrates serve the same purpose in the body, in that they furnish energy. Fats are not as easily digested as carbohydrates, but weight for weight they furnish two and one-fourth times as much energy.

Tests For Fats

Fats are readily tested with paper; if they are present in a given substance a permanent grease-spot appears. If to a suspected substance a little solution of caustic soda is added a white precipitate forms, representing a hard soda soap.