The nature and role of public health are constantly changing, and its definition has been a major preoccupation of public health leaders in the twentieth century. Essentially, public health is and always has been community action undertaken to avoid disease and other threats to the health and welfare of individuals and the community at large. The precise form that this action takes depends on what the community perceives as dangers to health, the structure of government, the existing medical knowledge, and a variety of social and cultural factors. From the beginning, communities, consciously or not, have recognized a correlation between filth and sickness, and a measure of personal and community hygiene characterized even the earliest societies.

By the eighteenth century, personal and community hygiene were becoming institutionalized. A wide variety of local regulations governed the food markets, the baking of bread, the slaughtering of animals, and the sale of meat and fish. These regulations were motivated by a concern for the poor, a desire for food of a reasonable quality, and commercial considerations. Bread was always a staple of the poor, and regulations in the Western world invariably set the weight, price, and quality of loaves. For economic reasons, merchants shipping food abroad promoted regulations on meat and grains in order to protect their markets and save themselves from dishonest competition.