They can eat a kosher diet, and be slaughtered the kosher way.
Kosher, when dealing with food and diet, simply refers to rules for the preparation and consumption of food. It has no bearing on the quality of diet itself. As such, there is nothing intrinsically good or bad about a kosher diet in terms of health.
The general meaning for kosher is "clean/fit or proper" and if you relate this to the cabbage soup diet, yes it is kosher and can help you stay healthy.
Keeping kosher.
Yes.
Keeping kosher.
See the links.
Judaism. See also:http://judaism.answers.com/jewish-laws/laws-of-keeping-kosher
There is nothing non-kosher in the ingredients for peanut butter and there are several brands of peanut butter that are certified kosher.
Kosher is the diet of Jews. Jews keep kosher. If you keep kosher you cannot eat: shellfish, pork, or dairy mixed with meat. The main land of Jews is Israel. So technically, the nationality of kosher is Israel.
Mostly Orthodox Jews
Normally, the difference is in the sweetener such as with non-diet Coke. In Diet Coke that is kosher for passover, Coke uses specific aspartame that is labeled as "kosher for passover". The equipment used to create the beverage is separate from that used to create Coke that is not kosher for passover, in accordance to passover law.