What Is Kosher Food?

From the Biblical Laws to Modern Practice

Matzah ball soup
Lauri Patterson / Getty Images

Kosher food is food prepared in accordance with Jewish Dietary Laws. 

While Jewish Dietary Laws originated in the Bible (Leviticus 11 and Deuteronomy 17), they have been codified and interpreted over the centuries by rabbinical authorities. At their most basic, modern-day Jewish Dietary Laws state the rules below. Here are the Kosher basics, according to the Torah: 

  • To qualify as kosher, mammals must have split hooves, and chew their cud. 
  • Fish must have fins and removable scales to be considered kosher.
  • Only certain birds are kosher. Generally speaking, they are birds that are non-predatory. 
  • This means pork, rabbit, eagle, owl, catfish, sturgeon, shellfish, and reptiles, among others, are non-kosher.
  • Nearly all insects are non-kosher as well though, per the Talmud, there are a small number of kosher locust species.
  • Kosher species of meat and fowl must be ritually slaughtered in a prescribed manner to be kosher.
  • Meat and dairy products cannot be cooked or consumed together.
  • A kosher food that is processed or cooked together with a non-kosher food, or any derivative of non-kosher food, becomes non-kosher. For example, food coloring derived from shellfish and used in a cake makes the cake non-kosher.
Illustration depicting kosher vs non kosher foods
The Spruce

Kashrut's Modern Evolution

Likewise, kashrut (kosher) practices have evolved in response to changes in the food industry, Jewish communal life, and world culture.

The growth of complex, industrialized food processing, international ingredient sourcing, and proprietary product formulations paved the way for today's kosher certifying agencies.

Kashrut agencies determine the kosher status of prepared foods and supervise manufacturing processes to ensure that certified products retain their kosher status. Kosher certification labels printed on food packages aid kosher-seeking consumers in navigating the food marketplace.

Different Definitions of Kosher Exist

As Jews lived in and adopted food traditions from different countries around the world and as different denominations of Judaism developed, Jewish definitions of kosher have become more varied over time.

There are different Jewish ethnic cultures, different branches within Judaism, and various Jewish kosher certifying authorities in the United States that certify kosher based on rules that vary from liberal to conservative.

Kosher Foods Sought by Non-Jewish People

Furthermore, in recent times non-Jews have become more interested in kosher food. Muslims, who account for 16 percent of the $100 billion-a-year U.S. kosher market, may buy a kosher food product because it fits the Quran's dietary laws of halal.

And people who are health-conscious may purchase something kosher because they believe it is healthier and safer as a result of the extra supervision. Various religious, cultural, health, and quality reasons spark their interest in and color their definitions of kosher.

Demystifying Kosher Food

Keep in mind that kosher is not a style of cooking. All foods—Italian, Chinese, French, etc.—can be kosher if prepared in accordance with Jewish law. Simply because a dish is associated with Jewish foods, such as knishes, bagels, blintzes, and matzah ball soup, does not mean it is kosher if not prepared in accordance with kosher law.

When a restaurant calls itself "kosher-style," beware. It usually just means that the restaurant serves these traditional Jewish foods, but that they probably are not kosher.