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The laws of Kashrut ("keeping kosher") are the Jewish dietary laws. Food in accord with Jewish law is termed kosher, from the Hebrew term kasher, meaning "fit" (in this context, fit for ritual purposes). Food not in accord with Jewish law is termed treif or treifah, meaning ritually unclean. (Also spelled trayf or treyf)

The basic laws of kashrut are in the Torah and their details are explicated in the oral law, contained in the Mishnah and the Talmud. According to the Biblical book of Leviticus, the purpose of the laws is related to ritual purity and holiness.

Table of contents

Theories on the origin of the Biblical dietary laws

The hygiene hypothesis

The laws of kashrut were once though to have been based on hygiene. It was believed by some that kosher animals were healthier to eat than non-kosher animals. It was also noted that the laws of purity (Leviticus 11-15) not only describe the difference between clean and unclean animals, but also describe other phenomena related to health. Thus, it was natural for many to assume that all the laws of kashrut were merely hygienic in intent and origin. However, this idea has fallen out of favor among biblical scholars for a number of reasons.

Such a rationale seems reasonable when considering the laws prohibiting the consumption of scavenger birds, which may carry disease from the carrion they; shellfish, which can contain parasites which can harm people, and pork, which can harbor trichinosis if not properly cooked. However, this hypothesis does not seem to make sense when one looks at the other laws of kashrut: They also forbid the consumption of birds of prey, which do not carry such diseases, and all fish without true scales, such as sharks. They even permit animals such as cows and sheep which also can harbor diseases which are dangerous to humans. In addition, this hypothesis does not explain the following parts of the Jewish dietary laws: Fruit from trees may not be eaten before the tree turns four years old; one must remove all blood from the meat; fruits and vegetables may be eaten without prohibition (even though there are many poisonous herbs, seeds, berries and fruits).

This is not to say that there could be no connection between the priestly laws of kashrut and hygiene. As in the dietary codes of many societies, it only makes sense that, over time, hygiene would likely play some role in the development of the dietary laws of Leviticus.

The symbolic laws hypothesis

During the first few centuries of the common era some philosophers held that the laws of kashrut were symbolic in character. In this view, kosher animals represent virtues, while non-kosher animals represent vices. The first indication of this view can be found in the Letter of Aristeas (par. 145-148, 153). This view later reappears in the writings of Philo of Alexandria, and in the writings of some of the early Church fathers. This hypothesis has long since been rejected by both Jewish and Christian scholars. Modern biblical criticism also has found nothing to support this hypothesis.

The laws as statutes without explanation or reason

"Some Jewish scholars have held that these dietary laws should simply be categorized with a group of laws that are considered irrational in that there is no particular explanation for their existence. The reason for this is that there are some of God's regulations for mankind that the human mind is not necessarily capable of understanding. Related to this is the idea that the dietary laws were given as a demonstration of God's authority and that man should obey without asking for a reason." (Source: William H. Shea, Clean and Unclean Meats, Biblical Research Institute, December 1988)

This view has been rejected by the majority of classical and modern Jewish rabbis, and by modern biblical scholars. For example, Maimonides holds that all the laws given by God have a reason, that we are permitted to seek out what these reasons may be, and that we should feel comfortable in knowing that rational reasons exist for all of God's laws in the Torah, even if we are not sure of what some of these reasons are. For Maimonides, the idea that God gave laws without any reason is anathema.

Laws serve as a religious and social distinction

One theory widely accepted today is that the laws serve as a distinction between the Israelites and the non-Israelite nations of the world. Gordon Wenham writes "The laws reminded Israel what sort of behaviour was expected of her, that she had been chosen to be holy in an unclean world." These laws had the added effect of preventing socialization and intermarriage with non-Jews, helping the Jewish community maintain its identity. Wenham writes that "circumcision was a private matter, but the food laws made one's Jewish faith a public affair. Observance of the food laws was one of the outward marks of a practising Jew, and this in turn enhanced Jewish attachment to them as a reminder of their special status." (Source: Gordon J. Wenham, "The Theology of Unclean Food," The Evangelical Quarterly 53, January March 1981, p.6-15.)

The Biblical explanation: Distinctions lead to holiness

According to the Biblical book of Leviticus, the purpose of the laws is related to ritual purity and holiness. Indeed, the Hebrew word for "holiness" is entymologically related to the Hebrew word for "distinction" or "separation". This idea is generally accepted by most Jews today, and by many modern biblical scholars. Cultural anthropologist Mary Douglas has written an important work on just how the Israelites may have used the idea of distinction as a way to create holiness. Her seminal work, Purity and Danger (1966), is still studied today.

Ethical and moral reasons

(To be added soon.)

How kashrut is viewed by Judaism today

Orthodox Judaism and Conservative Judaism hold that Jews should follow the laws of Kashrut. Reform Judaism and Reconstructionist Judaism hold that these laws are no longer binding. Most Jews in Reform Judaism have considered these laws a hindrance, rather than a facilitator, of piety; this is still the mainstream Reform position. Some parts of the Reform community have begun to move towards a more traditional position. This tradition-leaning faction agrees with mainstream Reform that the rules concerning kashrut are no longer binding, but holds that keeping kosher is an imporant way for people to bring holiness into their lives. Thus Jews are encouraged to consider adopting some or all of the rules of kashrut on a voluntary basis. The Reconstructionist movement advocates that its members accept some of the rules of kashrut, but does so in a non-binding fashion; their stance on kashrut is the same as the tradition-leaning wing of Reform.

Linguistic useage

In English, the term kosher is frequently used in a metaphorical sense to mean "acceptable" or "approved", which is its conventional meaning in Hebrew. It is also part of some common product names. For example, "kosher salt", which is a form of salt in large crystals that makes it particularly suitable for preparing meat in accordance with Kashrut law, and is not meant to imply that the salt itself is kosher in the original sense (although it is, as is normal table salt, sea salt, and just about any other form of salt).

Types of foods


Kosher mammals must both have cloven hooves and chew their cud. All kosher mammals are artiodactyl herbivores that can be domesticated, such as cows, goats, deer and sheep. The Torah specifies certain birds that are not kosher; in general, scavengers are considered non-kosher. The modern Halakha on kashrut classifies the flesh of both mammals and birds as "meat".

Jewish law states that kosher animals must be slaughtered according to a strict set of guidelines, the slaughter (shechita) being designed to minimize the pain inflicted. A professional slaughterer, or (shochet), uses a large razor-sharp knife with absolutely no irregularities, nicks or dents. A single cut is made across the throat, severing both carotid arteries, both jugular veins, both Vagus nerves, the trachea and the esophagus, usually causing death in 3-4 seconds. (If done improperly the death could take minutes; this is true for any method of slaughtering.) If the knife catches even for a split second, or is found afterward to have developed any irregularities, the animal is not kosher and is sold as regular meat.

Once killed, the animal is opened to determine whether there are any irregularities or growths on its internal organs, some of which can render the animal non-kosher. The word treif -- derived from the Hebrew treifah, meaning "torn" -- originally referred to animals which had not been properly slaughtered and prepared.

Large blood vessels must be removed, and all blood must be removed from the meat, as Jewish law prohibits the consumption of the blood of any animal. This is most commonly done by soaking and salting, but also can be done by broiling. An interesting fact, little-known outside of Jewish communities, is that the hindquarters of a mammal are not kosher unless the sciatic nerve and the fat surrounding it are removed (Gen. 32:33). This is a very time-consuming process demanding a great deal of special training, and is rarely done outside Israel, where there is a greater demand for kosher meat, since all meat sold in Jewish towns is required to be kosher by law. When it is not done, the hindquarters of the animal are sold for non-kosher meat.


Milk and milk-derived products derived from kosher animals are always kosher. All milk from cows is kosher. In practice, many Orthodox Jews use only "Cholov Yisroel" milk and dairy products; this label means that the milk has been under constant rabbinical supervision from milking to bottling, to make sure that it is not adulterated with the milk of a non-kosher animal. In the past this was a serious issue; today this is not a practical concern in the USA or in most western countries. As such, most Modern Orthodox rabbis and all Conservative rabbis hold that FDA supervision is sufficient for milk and dairy products to be considered automatically kosher.

No mixing of meat and dairy

Milk products and meat products may not be eaten together in the same meal, much less cooked together. Jewish law thus mandates a set of fence laws that prevent this from happening. Jewish homes have two sets of silverware, cookware, cups, and dishes. One is for milk (Yiddish milchig, Hebrew halavi) dishes, and one is for meat (Yiddish fleishig, Hebrew bsari) dishes. This prevents any trace of meat or dairy from being accidentally mixed. (Foods that contain neither milk nor meat are considered "neutral" -- Yiddish parev, Hebrew parve.)

Jewish law considers glass (and some say Pyrex) to be non-absorbent; thus, one could use just a single set of glass plates and dishes. In practice, this is rarely done not only because of the cost, but also because it is held that it would weaken the traditional system of kashrut observance. However, it is common even within the most religiously observant households to allow drinking glasses to be used for both dairy and meat meals, as long as they are thoroughly washed.

Various customs are observed for how long it is necessary to wait after eating meat before eating dairy foods again, and vice versa. Waits of three hours and six hours are the most common practices, though some communities wait only one hour.


All fresh fruits and vegetables are kosher. Jewish law requires that they be carefully checked and cleaned to make sure that there are no insects on them, as insects are not kosher (except Orthoptera, see below). In the last century the laws of kashrut have become much stricter in the Ultra-Orthodox Jewish community; they refuse to eat many vegetables, such as broccoli, because they hold that such vegetables are too difficult to remove tiny insects from.

Canned and frozen foods

Most such goods are usually permissible since manufacturers add only water and spices during the packaging process. Sometimes, however, fruits or vegetables are prepared with milk products or with non-kosher ingredients such as non-kosher meat broth. Orthodox Judaism thus holds that canned and frozen goods should generally not be consumed unless there is a heksher (mark of rabbinical certification of kashrut) on the product. Conservative Judaism often is more lenient, and holds that a careful reading of the ingredients is sufficient.

Grains and cereals

Unprocessed grains and cereals are kosher. Processed items (e.g. dry cereals, baked goods) often contain small quantities of non-kosher ingredients. As such Orthodox Judaism holds that these goods should generally not be consumed unless there is a heksher (mark of rabbinical certification of kashrut) on the product. Conservative Judaism often is more lenient, and holds that a careful reading of the ingredients is sufficient.

Grains and cereals during Passover

During the 8 days of Passover there are additional restrictions on what foods may be eaten. Jewish law forbids Jews from eating any leavened or possibly leavened product made from wheat, rye, barley, spelt, or oats.

An Orthodox discussion of the kitniot controversy (http://shamash.org/listarchives/mail-jewish/Special_Topics/kitniot)

An Israeli Conservative discussion of the kitniot controversy (http://www.responsafortoday.com/engsums/3_4.htm)

Rabbinical Assembly Passover guide (http://www.rabassembly.org/info/pesahguide/)


Eggs from kosher birds are kosher; they are also considered pareve (neutral; neither milk nor meat.) Eggs that contain blood may not be used. A partially-formed egg which is found inside of a slaughtered bird may be eaten, but it must undergo the same process of blood removal as the animal, and it is considered to be fleishig.


Kosher birds include: capon, duck (domestic), goose (domestic), chicken, turkey, guinea fowl and many others. As a general principle, scavenging birds such as eagles and vultures are not considered kosher, and others (generally) are.


With one exception, all bugs and insects are forbidden as treif (un-kosher). The exception is a type of locust from the Arabian peninsula; this type of locust encompasses four distinct species of locust. The tradition for identifying which species of locust were and were not kosher has been lost among all Jews except the Jews of Yemen.


Cheese made from milk and non-animal enzymes is kosher. But much cheese is made from milk and rennet, and the kashrut of such cheeses is a matter of debate in the religious Jewish community.

Rennet is the enzyme used to turn milk into curds and whey; most forms of rennet derive from the lining of the stomach of an animal, and thus are classified by most religious Jews as meat products. A vegetable substitute for rennet can be used, in which case none of these restrictions apply. Other Jewish authorities maintain another long standing Jewish legal tradition: rennet is held to be a secretion of the stomach wall, and thus does not have the status of meat. Further, in its normal processing, rennet undergoes a chemical change and becomes inedible, thus halakhically becoming a non-food. All foods in this category automatically lose any kashrut restrictions. They are considered to have changed so much from their original state that they are a d'var chadash, "a new substance" with properties significantly different from those of their original form. All such substances are considered pareve (neutral and kosher).

Fish and Seafood

To be kosher, a fish must have both fins and scales. The lack of either characteristic renders that species of fish unclean. Examples of unkosher fish include shark and catfish. All shellfish, such as crabs, lobster, and shrimp are not kosher. All sea mammals, such as dolphins, whales and seals are not kosher. All other sea animals, such as octopus, squid, jellyfish and eels are also not kosher.

Seaweed and other sea plant life are all kosher.

There are two fish that are controversial: Swordfish and sturgeon. Both of these have scales as young fish, but lose them later in life. Most Orthodox rabbis rule that these fish are not kosher; many Conservative rabbis rule that they are kosher.


A controversial topic is the status of gelatin. This substance comes from the processed bones of animals. If the source of gelatin is a kosher animal that was properly slaughtered according to Jewish law, then such gelatin is considered kosher by all Jews. All other gelatin is usually considered treif (non-kosher). However, a number of prominent rabbinic authorities have noted that gelatin undergoes such extensive processing and chemical changes that it no longer has the status of meat, and as such may be considered pareve and kosher. Most Conservative Jews, and a significant minority of Israeli Orthodox Jews, accept that all gelatin is kosher.


Many Jews choose to follow a vegetarian diet as their way of keeping kosher. Sometimes this is done for pragmatic reasons (red kosher meat is expensive and hard to come by in most cities and towns); often it is done for ethical reasons. Some prominent rabbis were vegetarian, such as the first Chief Rabbi of pre-state Israel, Abraham Isaac Kook.

Genesis 1:29 states "And God said: Behold, I have given you every herb yielding seed which is upon the face of all the earth, and every tree that has seed-yielding fruit - to you it shall be for food." According to many classical Jewish Bible commentators, this means that God's original plan was for mankind to be vegetarian. Rashi, one of the most important medieval Bible commentators, commnets on this verse "God did not permit Adam and his wife to kill a creature and to eat its flesh. Only every green herb shall they all eat together." This is also the view of mediveal commentators such as Abraham ibn Ezra (1092-1167), Maimonides (1135-1214) and Nahmanides (1194-1270). According to many rabbinic commentators, God later gave permission for man to eat meat because of man's weak nature, but the ideal would be for man to be vegetarian.

Kashrut and animal welfare

The method of slaughtering used in strict adherence to Jewish law has been criticized as being cruel by many animal rights organizations, in particular because animals are killed without the use of anesthesia. This has resulted in several restrictions or even an outright ban on kosher meat in a number of countries, though other countries grant ritualistic slaughter such as kashrut special exemption from the relevant regulations. However, some bans were in place before animal rights had become a general public concern.

Animal rights groups claim it can still take several minutes for the animal to die and thus would cause immense suffering. Jewish groups point to studies showing that the technique is no more painful than conventional techniques, and in most cases quicker and less painful; the conclusions of these studies are rejected by animal rights advocates. In addition, there are campaigns to have the practice of ritualistic slaughter globally banned [1] (http://www.viva.org.uk/Viva!%20Campaigns/Slaughter/goingforthekill2.htm).

Many Jewish organizations suspect that anti-semitism may also be an influence behind the efforts to ban kosher meat, partly because of a distinct anti-semitic element among the opponents of ritualistic slaughter, partly because of the age of some bans.

See also: Judaism

Further Reading

  • James M. Lebeau "The Jewish Dietary Laws: Sanctify Life" United Synagogue of Conservative Judaism, NY, 1983
  • Samuel Dresner, Seymour Siegel and David Pollock "The Jewish Dietary Laws" United Synagogue, New York, 1982
  • Isidore Grunfeld "The Jewish Dietary Laws" London: Soncino, 1972
  • Isaac Klein "A Guide to Jewish Religious Practice", JTSA, 1992
  • "Shechita: Religious, Historical and Scientific Perspectives" Munk, Feldheim Publishers, New York, 1976

External links

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