The substance in red blood cells that carries the oxygen to all regions of the body is made partly of iron and copper. Iodine is necessary in the functioning of the thyroid gland. All natural unrefined foods contain a variety of valuable minerals. But the refining of grains and the prolonged cooking of vegetables in a lot of water removes a great deal. The minerals most likely to be insufficient in the diet are calcium, iron and, in certain areas, iodine.
Calcium occurs plentifully in milk.
Iron is supplied by green, leafy vegetables, meats, fruits, whole grains, but more abundantly by egg yolk and liver. Vitamins are special substances that the body needs in minute amounts in order to work right somewhat the way any machine needs a few drops of oil, or a gasoline motor depends on a tiny electric spark. Vitamin a is necessary it keep healthy the linings of the bronchial, intestinal, and urinary systems, and various parts of eyes, including that which enables us to see in dim light. The body gets it plentifully from milk fat, egg yolk, green and yellow vegetables, vitamins drops. The four known to be most important for human beings are called by their chemical names now thiamin, riboflavin, niacin, pyridoxine.