Jewish dietary laws, known collectively as kashrut, govern which foods observant Jews may eat and how those foods must be sourced, slaughtered, prepared, and combined. The word “kosher” is Hebrew for fit or proper, and the rules draw from the Torah, especially Leviticus 11 and Deuteronomy 14, as developed by centuries of rabbinic interpretation. In practice, kashrut touches almost every meal: it determines which animals are permitted, requires a specific method of slaughter, forbids mixing meat with dairy, and adds further restrictions during Passover.
Which Animals Are Permitted
Land animals must meet two physical criteria at once: fully split hooves and the chewing of cud.1Bible Gateway. Leviticus 11, Deuteronomy 14 – Clean and Unclean Food One trait is not enough. The pig has split hooves but does not chew cud, and the camel chews cud but lacks fully split hooves, so both are forbidden. Cattle, sheep, goats, and deer qualify.
Fish must have both fins and scales, and the scales must be the removable kind that peel off without tearing the skin. Sturgeon and swordfish are excluded on that basis.2Chicago Rabbinical Council. Fish – Purchasing Shellfish, crustaceans, and aquatic mammals are all out.
Birds work differently. The Torah lists specific forbidden species, mostly raptors and scavengers, and any bird not on the list is in principle allowed.3Chabad.org. Why Are Grasshoppers/Locusts Kosher for Some Jews In practice, you can only eat a bird if a received communal tradition, called a mesorah, confirms it as kosher. Chicken, turkey, duck, and goose are universally accepted. Guinea fowl and peacock are not.4OU Kosher. OU Position on Certifying Specific Animals and Birds
Insects are almost entirely forbidden. The Torah permits certain species of locusts and grasshoppers, but most communities today avoid even those because reliable identification is difficult. The practical result is that leafy greens, herbs, and berries have to be washed and inspected carefully for small insects and larvae before cooking.
How Meat Becomes Kosher
A permitted species is only the starting point. The animal must be slaughtered by a trained specialist called a shochet, using a method known as shechita: a single continuous cut across the throat with a perfectly smooth blade called a chalaf. Any nick in the blade, hesitation, or excessive pressure invalidates the slaughter.
Afterward, the shochet inspects the animal, paying particular attention to the lungs. Adhesions, perforations, or disease classify the animal as treifah and unfit to eat.5Chabad.org. What Inspection Does the Shochet Perform at and after Shechita Meat labeled “glatt kosher” comes from an animal whose lungs had no adhesions. “Glatt” is Yiddish for smooth. Ashkenazi practice allows up to two small, easily removable adhesions and still calls the meat glatt; Sephardi practice follows a stricter standard, glatt Beit Yosef, that does not allow those leniencies. For lamb, veal, and kid, both traditions require the stricter standard.6OU Kosher. Whats The Truth About Glatt Kosher
Consuming blood is forbidden, so kosher meat is treated to extract it. The meat soaks in room-temperature water for at least 30 minutes, then is covered on all sides with coarse salt on a slanted board or rack so the drawn-out blood drains away. The salt stays on for at least one hour, after which the meat is rinsed three times.7Chabad.org. Koshering Meat
Certain internal fats, called chelev, and the sciatic nerve must also be removed through a skilled process called nikkur, or porging.8OU Kosher. Whats The Truth About Nikkur Achoraim Because removing the sciatic nerve from hindquarter cuts is technically demanding, most kosher meat sold in the United States comes from the forequarter.
Keeping Meat and Dairy Apart
The Torah states three times, “You shall not boil a young goat in its mother’s milk.”9Bible Gateway. Deuteronomy 14:21 ESV Rabbinic tradition derived three prohibitions from the repetition: cooking meat and dairy together, eating them together, and benefiting from the mixture. Every food, as a result, falls into one of three categories. Fleishig is meat. Milchig is dairy. Pareve is neutral, covering fruits, vegetables, grains, eggs, and fish, and can be eaten with either meat or dairy.
Keeping the categories separate shapes the kitchen itself. Most kosher households keep two complete sets of cookware, dishes, and utensils, often color-coded, with separate sinks, dish racks, and sponges.
Waiting Between Meat and Dairy
After eating meat, the standard practice is to wait six full hours before any dairy, though some communities follow shorter customs.10Chabad.org. Waiting Periods Between Meat and Dairy The reverse direction is much shorter for soft dairy: rinse your mouth, eat something solid like bread, wash your hands, and some customs add a half-hour wait. Hard aged cheese, aged six months or more, is the exception and requires a full six-hour wait before meat.11Chicago Rabbinical Council. How Long Must I Wait
Wine, Bread, and Cooked Foods
Wine has its own category because of its historical ritual use. Non-mevushal kosher wine, once opened, must stay under Jewish supervision; if a non-Jewish person moves or handles the open bottle, the wine becomes forbidden. Mevushal wine, which has been heated to a sufficient temperature (modern pasteurization meets this threshold according to many authorities), can be handled freely by anyone without losing its status.12OU Kosher. Mifustar – Is It Mevushal That is why most kosher wine poured at catered events and restaurants is mevushal. Sealed bottles can be moved by anyone regardless.
Some foods also require that an observant Jew participate in cooking them, even when every ingredient is already kosher. Bread made from the five primary grains, which are wheat, barley, oats, rye, and spelt, ideally qualifies as pat Yisrael, meaning a Jewish person was involved in the baking. Lighting the oven or placing the dough inside is enough; preparing the dough alone does not count.13STAR-K Kosher Certification. Pas Yisroel Guidelines A parallel concept, bishul Yisrael, applies to cooked foods considered dignified enough to serve at a formal meal: turning on the stove, lighting the pilot, or flipping a switch that directly ignites the heat source all qualify, though actions that only indirectly cause an oven to light do not.14STAR-K Kosher Certification. Food Fit for a King – Reviewing the Laws of Bishul Akum/Bishul Yisroel
How to Tell if a Product Is Kosher
Modern food manufacturing uses thousands of ingredients, so individual shoppers cannot verify every product on their own. Certification agencies employ supervisors called mashgichim who monitor facilities, audit ingredient sources, and verify production lines. A product that passes carries a hechsher, a printed certification symbol. Common marks include the OU (Orthodox Union), OK, and Star-K.
These symbols have legal backing. Several states have enacted kosher fraud laws authorizing regulators to levy fines and order product withdrawals when a manufacturer falsely marks goods as kosher, and federal trademark and consumer protection laws add further enforcement tools.15OU Kosher. The Unauthorized Kosher Symbol You can rely on recognized certification symbols with reasonable confidence when shopping.
Passover Adds More Restrictions
During Passover, chametz is forbidden. Chametz is any product made from wheat, barley, rye, spelt, or oats that has been in contact with water long enough to begin fermenting. The working threshold is 18 minutes: matzah bakeries make sure no more than 18 minutes pass between the flour touching water and the dough entering the oven.16OU Kosher. Matzah 101 The Torah commands eating unleavened bread for seven days of the holiday,17BibleHub. Exodus 12:15 and Jewish communities outside Israel observe an eighth day based on an ancient calendrical safeguard that became permanent custom.18Chabad.org. Why Is Passover Seven or Eight Days Long
The restriction extends past eating. You cannot own chametz, benefit from it, or keep it in your home, so observant households clean thoroughly before the holiday and either consume, sell, or destroy any remaining leavened products.
Ashkenazi tradition goes further by avoiding kitniyot during Passover, a category that includes legumes, rice, corn, and similar foods. The historical concern was confusion with prohibited grains or stray grain mixed in. Sephardi communities never adopted the restriction and eat kitniyot freely on Passover.19Orthodox Union. When Do Passover Dietary Laws End In 2015, the Conservative movement’s Committee on Jewish Law and Standards formally ruled that Ashkenazi Jews may eat kitniyot on Passover, citing the original concern’s inapplicability in modern food production. The ruling still calls for checking dried goods for stray grains of chametz and notes that processed kitniyot products need Passover certification.
When Health Overrides the Rules
Jewish law treats preserving life as an overriding obligation. The principle of pikuach nefesh means that virtually any commandment, including dietary restrictions, is set aside when a person’s life is in danger, and a patient who needs non-kosher food for recovery is permitted to eat it.20Jewish Virtual Library. Pikuach Nefesh
Medications sit in a more nuanced zone. Many pills and supplements use gelatin capsules derived from non-kosher animal sources. Someone who is genuinely ill and has no gelatin-free alternative may use the medication, because the capsule is consumed in an atypical way rather than as food. Someone taking vitamins purely for general wellness does not have the same leniency.21Chicago Rabbinical Council. Gelatin Capsules The sicker the person, the more latitude the law provides.