Kilayim Pie?

The prohibition against interbreeding animals and plants raises questions about the kashrut of genetically modified foods.

Commentary on Parashat Achrei Mot-Kedoshim, Leviticus 16:1 - 20:27

Provided by, an on-line Jewish magazine dedicated to pursuing justice, building community, and repairing the world.

I have always had a fond feeling in my heart for the talmudic Rabbi Yermiah. He always asks the kind of questions that would drive people to distraction in any era.

The Talmud says that if you find a dove sitting on the ground within 100 yards of a dovecote (a roost for domesticated pigeons), you ought to assume that the dove belongs to the owner of the dovecote and return it. If you find it more than 100 away, you can assume that it is in the public domain and take it. Rabbi Yermiah asks: What if you find it lying with one foot over the 100 yard line and one foot within the 100 yard line?

The other rabbis of the Talmud got so frustrated with Rabbi Yermiah that they eventually kicked him out of the house of study. But they soon realized that they needed somebody to ask those kinds of questions, and they grudgingly let him back in. After all, if you are going to set limits, it is important to consider the cases that may defy or challenge those limits.

It was in the spirit of Rabbi Yermiah that I recently asked a number of organizations that certify processed foods as kosher if they took into consideration whether the fruits, grains, and vegetables used in the products are genetically modified. As Rabbi Yermiah might have put it, we know that a tomato is kosher, but when does a tomato cease to be a tomato?

This is not as far-fetched as it may sound. The Torah proscribes the interbreeding of animals and plants. "You will keep my laws; you will not breed your animals as kilayim [the junction of two inappropriate things], you shall not seed your fields as kilayim (Leviticus 19:19).

The debate over the marketing of genetically modified organisms (GMOs) has recently intensified in Canada. Many Canadians are increasingly concerned not only that the food we buy is treated extensively with pesticides and herbicides, but also that the genetic makeup of vegetables, fruits and grains is being altered to produce larger yields. In some cases, this means using new technologies to graft genetic components not only from other types of the same plant, but from entirely different species.

Some Canadians are arguing that food producers should be required to label the foods that contain genetically modified products, and let consumers choose for themselves when they go to the grocery store. One man in the United States has sued the Federal Department of Agriculture to require labeling of products containing genetically-modified foods, on the grounds that because of the laws of kilayim, his religious freedoms as a Jew are being violated if he cannot distinguish between GMO’s and non-modified foods.

It has generally been held that the Torah’s agricultural restrictions only apply within the land of Israel. With respect to kilayim, the majority of rabbis through the ages have held that as long as one is not actively involved in the process of making the forbidden alterations, one can derive benefit from the changes once they have been made. One should not set out to make a kosher pig by crossing a pig with a cow, but if one were ever made, we could have bacon on Sunday mornings.

However, as Nahmanides, the 13th-century Spanish-Jewish commentator points out, the laws of kilayim point to a basic Jewish understanding of the world we inhabit. We arrived at consciousness in this world with species in all their variety in place, and we ought to proceed with extreme caution. They exist because God wants them here, and we proceed at our own peril if we set out to alter them.

The organizations that supervise the religious suitability of foods for Jewish consumers–what are they doing about the issue of genetically modified food? What answer did I get to my own Rabbi Yermiah question?

Two of the major organizations did not respond to my emails. The Star-K of Baltimore did reply saying, "…As a rule we do not assume that commercial produce is grown in a prohibited manner. The bottom line is, if it looks like a tomato and smells like a tomato, it is a tomato and may be eaten."

It remains for the Rabbi Yermiah in each of us to decide whether we are satisfied with this answer.

Discover More

Gittin 84

You can have your divorce when pigs fly.

Gittin 51

Wallets and oxen.

Kiddushin 73

How to avoid being pelted with etrogs.