Though a mixed diet is advised, there is a distinct choice in the desirability of the animal foods eaten. Less red meat is urged; it contains substances (extractives) that are stimulating rather than nourishing. In moderation their stimulation may sometimes be wholesome. In excess it is disadvantageous; it harms, whereas food that nourishes helps the body to grow, to care for its own action, and to do the work the person does. Eggs, milk, and milk-products, as cheese, are animal foods without extractives, as are also white meats, such as poultry and fish.

It is sometimes stated that some nations, and such of all nations as are very limited in their food-supply, live mainly, if not entirely, upon a vegetable diet and secure their building-food material from grains. Science finds this is not the general practice anywhere. Rice in the Orient is supplemented by fish and poultry, the potato of Ireland by bacon, the grain foods of the workers of continental Europe by cheese, the corn-meal of our Southern states by eggs and poultry.

Wherever fresh meat cannot be kept or afforded, animal foods that can be found or raised are everywhere somewhat used. On the seacoast and along streams fish abound and are eaten. Inland game and the products of domestic animals, as milk and eggs, are eaten where the animals themselves would be too costly for food, or for other reason would not be so used.

Grains thoroughly masticated after being thoroughly cooked build the body. Yet alone they cannot do all that is done by a mixed diet. To the young it brings foods prepared by nature for animal young, as are milk and eggs. While children are themselves being formed and learning to eat adult-diet, they need such nature-prepared building food. Mixed diet also makes, for all, body-tissues that retain elasticity in advanced age. Such tissue not only lasts long but is capable of prolonged activity.