In the Jewish faith, food preparation is performed according to laws and customs, called "Kashrut," passed down since Biblical times. In Jewish tradition, these laws have no explicit meaning; they are of a class of law called "Chuk," which defines laws that are accepted on faith. Many scholars have tried to interpret meaning for kashrut laws. For example, some believe they were created by God to separate the Hebrew people from other tribes; others believe that the laws allow a higher spiritual standard because the food is prepared properly, without non-kosher and spiritually-contaminated ingredients such as pork.
One very plausible explanation for kashrut is that it allowed food to be prepared according to hygienic standards; food preparation throughout history is of varying cleanliness, and kashrut standards enabled fewer food-borne illnesses. This theory is held up by certain historical facts, such as the disease Trichinosis, which was often caused by parasites in pork; by avoiding pig products altogether, the disease is largely avoided. Similar health claims come from the kosher law of extracting all (or almost all) the blood from an animal before cooking it; this helped to avoid blood-borne disease, especially when food was not fully cooked before consumption.
Kashrut laws are up for interpretation, but they have survived intact for thousands of years and remain important to Judaic custom. Since they cause no harm, and can be helpful (for example, for restricted dietary needs), their spiritual or secular meaning is ultimately one of faith.