Judaism believes that keeping healthy isn't just good advice; it's biblically required as an all-important mitzvah.
The man Jews admire as the closest to Moses in the Bible, the 12th-century Spanish Rabbi, philosopher and scholar, Moses Maimonides (1135 – 1204) was a great physician by profession. He authored a book summarizing all of Jewish law. In it he wrote: "Since it is impossible to have any understanding and knowledge of the creator when one is sick, it is one's duty to avoid whatever is injurious to the body and to cultivate habits that promote health and vigor." He then went on to list medical do's and don'ts that read like the health letter from the Mayo Clinic – and that have become an essential part of the Jewish code of law. That's why Jews have so often become doctors. And that's why cleanliness isn't just next to godliness; it's a precondition for spirituality.