This is the most important cereal grain in the diet of more than half of the human race, especially that portion of the race in Asia and the islands of the Pacific, and is used to a considerable extent throughout the world. It has never found much favor in the United States, but is used in small amounts. Among primitive peoples rice is eaten without polishing, in which form it is known as red rice, but it is ordinarily so treated as to lose a large part of its germ. This loss results from the pounding of the kernels in rude mortars in which process the germ is separated from many of the kernels and lost in subsequent handling. The bran layer, which is richer in mineral salts than the endosperm of the seed, is retained in this process.

Rice which is used for export and for sale in the large cities at some distance from the place of production, is polished by stirring the kernels. The abrasive action results in wearing away the bran. The germ is in an exposed position and easily rubs off in this process and is, therefore, left with the bran. This mixture is known as rice polishings. The germ of rice, like that of wheat or maize, consists of cellular structures which are the seat of protoplasmic activity, and is a more complete food than any other part of the kernel. It contains almost all the fats found in the grain, and is more efficient in nourishing insects as well as higher animals than is the polished grain. Unpolished rice loses its flavor owing to the fats becoming rancid, when kept for considerable periods in a warm climate, whereas the polished kernel can be handled without commercial hazard because it contains almost no fat and does not support the growth of insect larvae.

The practice of polishing rice had its origin in the desire to improve its keeping quality, and the incidental whitening of the kernels has led to the establishment of a demand for a white product. This, and the artificially established liking for white flour and white corn meal, is an illustration of the failure of the instinct of man to serve as a safe guide in the selection of food. The esthetic sense is appealed to in greatest measure in this case by the products of lowest biologic values.

Attractiveness of rice to the eye is so important a factor commercially that the practice of artificial whitening of the polished kernels has come into vogue. This is accomplished by coating the kernels with talcum powder, the latter adhering by means of a thin coating of glucose. The milky appearance of the water in which rice is washed, is due to the talcum remaining for a time in suspension. Rice which has been polished but not coated in this way is called brown rice as contrasted with the coated or white rice.

Chart 3 shows that there are four dietary factors in which polished rice is of such poor quality as to require improvement before it becomes a complete food. Its proteins like those of other cereal grains are of low biological value, and need to be enhanced by the addition of other proteins which are so constituted as to have a supplementary relationship to rice proteins (11). It is entirely too poor in all essential mineral elements to meet the needs of a growing animal, and is nearly free from both fat-soluble A and water-soluble B. The experimental data in Chart 3 was obtained with the rat and does not bring out the fact that rice is lacking in the anti-scorbutic substance. This substance is not essential in the diet of the rat for the reason that this animal is able to synthesize the complex, whereas man, monkey and guinea pig must secure their supply from the food. This point will be further discussed in Chapter VIII (The Dietary Deficiency Diseases Scurvy. 178. The Relation Of The Diet To Certain Diseases Has Long Been Suspected) in connection with the deficiency disease scurvy.

130. Barley And Rye

These and apparently other cereal grains possess essentially the same dietary properties and shortcomings as do those already described. Experiments with animals have shown that they must be improved in respect to the same factors in order to make them complete foods (12).