Our bodies are built up from the food we eat. There is a constant breaking down of the tissues of the body; every movement of every organ involves waste, and this waste is repaired from our food. Each organ of the body requires its share of nutrition. The brain must be supplied with its portion; the bones, muscles, and nerves demand theirs. It is a wonderful process that transforms the food into blood and uses this blood to build up the varied parts of the body; but this process is going on continually, supplying with life and strength each nerve, muscle, and tissue. CCh 221.1
Those foods should be chosen that best supply the elements needed for building up the body. In this choice, appetite is not a safe guide. Through wrong habits of eating, the appetite has become perverted. Often it demands food that impairs health and causes weakness instead of strength. We cannot safely be guided by the customs of society. The disease and suffering that everywhere prevail are largely due to popular errors in regard to diet. CCh 221.2
But not all foods wholesome in themselves are equally suited to our needs under all circumstances. Care should be taken in the selection of food. Our diet should be suited to the season, to the climate in which we live, and to the occupation we follow. Some foods that are adapted for use at one season or in one climate are not suited to another. So there are different foods best suited for persons in different occupations. Often food that can be used with benefit by those engaged in hard physical labor is unsuitable for persons of sedentary pursuits or intense mental application. God has given us an ample variety of healthful foods, and each person should choose from it the things that experience and sound judgment prove to be best suited to his own necessities.375The Ministry of Healing, 295-297 CCh 221.3