The main things in a Kosher diet are as follows:
Not eating meat from any animal that does not both chew its cud and have split hooves. (examples: pigs, rabbits, horses)
Not to mix dairy and meat.
Not to eat any meat or chicken not slaughtered in the correct way.
There are other specific things that aren't kosher such as shell fish, or any fish without fins and scales. Only certain animals are kosher.
The more religious, the more stringent the laws are. Such as only eating food made by a Jew. Or not eating products that contain ingredients that may have been derived from an animal source.
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.
Leviticus 11
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