Hydrocarbon foods are those rich in hydrocarbon--fats and oils. Hydrocarbons are composed of carbon, hydrogen and oxygen. In the animal body, fats may be manufactured out of sugars and proteins. Fats are produced in the plant out of sugar. Chief among the hydrocarbon foods are:

Fruits--olives, avocados.

Nuts--almost all varieties.

Legumes--peanuts, soy beans.

Dairy products--cream, butter and some cheese.

Flesh of dead animals, especially pork and mutton and beef that has been fattened. Fat fish--herring, shad, salmon, trout.

There are many kinds of fats--solid and liquid. Fats and oils are formed in plants, and fruits when ripening. A decrease in sugars accompanies the increase in fats. It is but another evidence of the importance of sugar in the life of the plant and, thereafter, in the life of the animal. While the animal is capable of synthesizing fats out of starches and sugars, it is not capable of taking hydrogen, oxygen and carbon and synthesizing fats out of these.

The fat of the animal differs from the oil of the plant, just as do the proteins of the animal differ from those of its food supply. Each animal builds its own characteristic fats out of its foods. Fats and oils are complex substances that are made up of simpler substances which we may call the "building stones" of fat. True fats are composed of fatty acids and glycerol--or glycerides. Fats differ according to the fatty acids and glycerides which they contain.

Stearic, palmitic butyric and oleac acids are the most common glycerides found in edible fats. The stearates are combinaitons of stearic acid with glycerol--stearin. Several fatty acids are present in all fats. In butter there are palmitic, oleic, myristic and butyric acids. Stearic acid is present in suet (hog fat), palmitic acid is abundant in vegetable and animal fats. Oleic acid is found in most fats and oils. Such vegetable oils as olive, cottonseed, peanut, almond and cocoanut oils contain large amounts of olein.

Fats are split up during the process of digestion into fatty acids and glycerol. Fats and oils, like proteins and carbohydrates, are not usable as such, but must be broken down into their constituent "building stones" and these "building stones"--fatty acids and glycerol--are used with which to build human fats.

Mendel asks "are there essential fatty acids that must be supplied in the diet because they cannot be produced de novo by the animal organism?" Although both he and Hindhede have shown that green stuff can take the place of fat in the diet, there are facts that lead us to believe that it is, at least, a great saving to the body if some fat is supplied.

Although the body can synthesize fats out of carbohydrates and proteins, there are certain fatty acids that it is incapable of synthesizing and these are essential to animal life. Three unsaturated fatty acids--linoleic, linolenic and arachaidonic--cannot be synthesized by the animal organism. Only one of these is considered essential, for, as in the case of certain amino acids, they can replace one another in animal nutrition. Rats fed on diets lacking in the essential fatty acids cease to grow, develop scaliness of the skin, caudal necrosis, emaciation, kidney lesions and early death. Certain blood deficiencies are also seen when these fatty acids are lacking in the diet of animals.

Besides the fatty acids supplied by the fats in our diet, fats also contain fat soluble vitamins and minerals. Large quantities of fat are not required, but a small quantity daily is essential to normal development and maintenance and to good health.

Fat serves as a protection and as a packing and support for organs, forms emulsions and lubricants, serves as storage for reserve "fuel," enters into the constituents of the walls of the body's cells, and is an essential element of the nervous system. Lecithin, a widely distributed fat is very important in human nutrition, being an essential ingredient of the brain and nerves and also of the semen. Lecithin contains, besides the fatty acids, phosphorus. Insufficient fat tends to lessen nervous efficiency.

On the whole, vegetable oils are superior to animal fats as human foods. Cream and butter (unpasteurized) are the best of the animal fats employed as foods. Fats, like sugars, are best taken as nature prepares them; that is in the foods in which they exist. Most nuts are rich in oil and form the best sources of fat for human consumption. Fats, when extracted from their sources, concentrated, purified, and preserved, form poor foods. Many of them have all their vitamins destroyed and are devoid of all minerals. For example, in the process of rendering hog fat into lard, the fat is boiled for a long period and everything skimmed from the top until nothing remains but "pure" fat. All the minerals and vitamins are destroyed and removed. Long cooked in this way, the lard is practically indigestible. Olive oil, peanut oil, soybean oil and other vegetable oils are best eaten in the fruits, legumes and other plant substances in which nature prepares them.

Fats must be digested before they can be used. The cells of the body cannot use complex fats. The fats must first be reduced to a few simple acceptable substances in the process of digestion. The skin is not a digestive organ. It is not able to take complex fats and break them down into their simpler constituents and then make use of the fatty acids and glycerol thus formed. For these reasons "skin foods," composed of some cream or oil, to be rubbed on or into the skin, cannot nourish the skin. They only grease it--that is, make it dirty. The skin must be fed from within. It contains very little fat and this must come from the blood. Blood is the only food of the tissues of the body. It is folly to try to feed our tissues with any other substances.