The idea that diet is an important factor in health is a very old one and, if anything, had greater promi­nence in the time of Hippocrates than it does now.

However, the development of a workable system or science of nutrition had to await the development of modern chemistry with its significant advances at the end of the eighteenth century.

Before that time, the purpose of nutrition in adults was assumed to be the replacement of abraded (or worn-out) tissues. Meat, the tissues of other animals, seemed an effective food for this pur­pose, because it provided essentially like-for-like, but vegetable foods seemed to be made of quite differ­ent “stuff.” Animal tissues allowed to decompose became putrid and alkaline, whereas most vegeta­bles became acid and did not become putrid. When heated and dried, animal tissues became hornlike, whereas vegetables became powdery. However, Iacopo Bartolomeo Beccari of the University of Bolo­gna pointed out in 1728 that, when sieved (i.e., debranned) wheat flour was wetted and pummeled into a dough and then kept under running water until the floury starch had been washed out, the residual gluten had all the properties of animal tis­sues. Similar fractions were found in other plant foods. It was thought that these were the essential nutrients, and it was the job of the digestive system to winnow away the unwanted starch, fiber, and so forth and leave the glutenlike material to be circu­lated in the blood, for patching and filling.