What It Means to Keep Kosher
A practical, thoughtful guide to the deeper meaning and daily practice of keeping kosher
When people hear the word “kosher,” many think of just one thing: separating meat and dairy. But the Jewish dietary laws are far more expansive and form a detailed and meaningful system that shapes not only what we eat, but how, when, and even why we eat.
At its core, keeping kosher is about elevating the physical act of eating into something spiritual. As the Torah commands, “You shall be holy people to Me” (Shemot 22:30). The Sages explain that if we distance ourselves from forbidden foods and maintain dietary purity, we belong to God; if not, we forfeit that closeness. In other words, the path to holiness runs straight through the kitchen.
Why We Keep Kosher: Three Layers of Meaning
While the primary reason for keeping kosher is simply because the Torah commands us to, keeping kosher also has physical, emotional, and spiritual benefits:
1. Physical well-being Modern research has shown that kosher standards can support health. For example:
2. Emotional and moral discipline Keeping kosher builds restraint. You can’t eat anything, anywhere. You need to check, ask, and sometimes wait. This cultivates patience and intentionality. Every time that you pause before eating, you affirm that you’re not led by impulse alone. You’re engaging your moral awareness.
3. Spiritual clarity Our Sages taught that non-kosher food dulls the heart and numbs a person’s sensitivity to holiness and distance from God. Rabbi Yishmael even suggested that the entire Exodus from Egypt was worthwhile to prevent the Israelites from eating spiritually damaging foods (see Rashi’s commentary on Vayikra 11:45).
In short, kosher eating uplifts the body, mind, and soul.
Eating Mindfully
To make meals more meaningful, it is helpful to ask four questions before eating:
The Basics of Kosher Food: What It Involves
1. Ingredients and Processed Foods
While raw natural items like salt are generally kosher, modern food manufacturing complicates things. Many products contain flavorings, stabilizers, and additives—some of which come from non-kosher sources (like a bright red food dye made from insect blood). That’s why reliable kosher certification is so essential.
2. Plants and Produce
All fruits and vegetables are inherently kosher. The primary concern today is insects. Since the Torah forbids eating bugs, leafy greens (like lettuce, parsley, strawberries, and broccoli) must be washed and checked thoroughly. Many kosher-certifying agencies offer pre-washed, bug-free produce labeled accordingly.
3. Meat and Poultry
Only certain animals are kosher, and even they must be slaughtered properly by a trained, God-fearing shochet (ritual kosher slaughterer). If the animal was injured or sick, it may be deemed treif (non-kosher). Even after proper slaughter, some parts (like certain fats and sinews) are forbidden. Blood must also be removed through a salting process.
4. Dairy and Eggs
Kosher milk and kosher eggs only come from kosher animals. Eggs must be checked to ensure there aren’t any blood spots. As with all food today, dairy production has become more complicated, and all dairy products must be certified kosher.
5. Meat and Dairy Separation
The Torah prohibits cooking, eating, or benefiting from meat and milk together. Rabbinic law extends this to poultry as well. That’s why kosher kitchens maintain complete separation of meat and dairy utensils, pots, and even sinks. Wait times after eating meat before consuming dairy vary by custom—the most prevalent custom is six hours, though some only wait three hours, and Jews of Dutch descent only wait one hour.
It is not necessary to wait a similar amount of time between dairy and meat, and it is sufficient to rinse one’s mouth and wash one’s hands.
Interestingly, this separation has a health benefit too: calcium (from dairy) and iron (from meat) compete for absorption. Eating them separately improves nutritional efficiency.
6. Fish
Fish are not considered meat in kosher law, so they can be eaten with dairy (though some Sephardic Jews avoid this). However, fish and meat should not be eaten from the same plate or with the same utensils, due to ancient concerns about digestion.
Keeping a Kosher Kitchen
Beyond what we eat, how we cook and serve food matters. A kosher kitchen includes:
Appliances like ovens and countertops must be used with care. If a kitchen has not been kept kosher, it may be kashered (made kosher) through a process involving heat or boiling water, depending on how the item was used. In general, the way a utensil was used is the way it needs to be made kosher. For example, a metal spoon that was used to stir both dairy and meat hot liquids can be made kosher through immersion in a pot of boiling water. An oven rack that was used with both dairy and meat items must be made kosher by immersing it in fire (e.g., using a blow torch).
Some materials (like certain ceramics or Teflon) cannot be made kosher. In such cases, it’s best to consult a rabbi. Some communities offer free koshering services to help people start fresh.
Immersing Utensils
Any utensil made of metal or glass and manufactured by non-Jews must be immersed in a mikveh (ritual bath) before use. This symbolizes its transition from ordinary to sacred use, just like a person converts to Judaism through immersion.
Only items that come in direct contact with food (such as forks, knives, pots, and parts of electrical appliances that directly touch food) require immersion. Labels, stickers, and any residue must be removed beforehand. Many ritual baths have a special area for immersing utensils.
One of the deeper ideas behind keeping kosher is the development of inner refinement and self-control. A kosher lifestyle demands conscious restraint. Before putting anything into our mouths, we must pause, check, and think. And it turns out that this kind of restraint comes with significant benefits.
One famous study that highlights this was the “Marshmallow Test,” conducted by psychologist Walter Mischel in 1970. In the experiment, young children were each offered a marshmallow and told that if they could resist eating it for a set period of time, they would receive two marshmallows instead. Each child was then left alone for twenty minutes while being observed on camera.
The results were striking: only about one-third of the children were able to wait the full time, while the rest gave in to temptation. But the real insight came years later, when researchers followed up to see how these children had fared in life.
Those who had successfully delayed gratification turned out to do significantly better across the board. They achieved more in their careers, had better mental health and family stability, and reported higher levels of overall happiness compared to their peers who had not been able to wait.
In the same way, keeping kosher is about more than just food—it’s about training the soul. It’s a daily opportunity to build the muscle of restraint, to strengthen our capacity for patience, discipline, and spiritual awareness.
According to halacha (Jewish law), “One witness is deemed credible with regard to prohibitions” (Gittin 2a). In other words, when it comes to what is permitted or forbidden to eat, we can rely on the word of someone who is knowledgeable and God-fearing. That’s exactly the role of the kosher supervisor (known as the mashgiach): a trained and trusted individual who verifies that the food is indeed kosher.
The kosher supervisor oversees every aspect of food preparation at a restaurant or food establishment, from checking the kosher status of ingredients to ensuring that all laws of kosher are observed throughout the preparation and cooking process.
The Torah provides clear criteria for identifying kosher animals and, in some cases, even lists specific species by name. These signs are not arbitrary. They reflect a consistent Torah law that has been preserved for generations.
Land Animals: Two Required Signs
For an animal to be kosher, it must meet both of the following conditions:
The Torah makes a remarkable claim: every land animal in the world either has both signs or neither. Only four animals have one sign but not the other—and the Torah names them specifically to avoid confusion: the camel, the hyrax, the hare, and the pig. All are non-kosher.
Fish: Fins and Scales
A kosher fish must have both fins and scales. This rules out shellfish, crustaceans, and all forms of seafood labeled as “non-fish” (shrimp, crab, lobster, etc.).
A fascinating halachic principle emerges from this category: “Any fish that has scales will also have fins, but some that have fins may not have scales” (Niddah 51b).
In other words, if a fish has scales, it is kosher, because it is guaranteed to have fins as well. This is a testable scientific claim. And as of today, over 34,300 species of fish have been discovered, and not one contradicts this rule. Only the Creator of all marine life could have embedded such a universal law into the text of the Torah thousands of years ago.
Birds: Tradition Is the Guide
Unlike land animals and fish, the Torah doesn’t give specific physical signs to identify kosher birds. Instead, it lists the names of non-kosher species. Over time, the precise identification of many biblical bird names was lost. Therefore, in modern practice, only birds with a clear and continuous tradition of being kosher are permitted.
The Hidden Risks of Dining Without Certification
Even if the food looks kosher and there’s a picture of a rabbi on the wall, without kosher supervision, you never really know what’s going on in the kitchen.
Take, for example, a story shared by one of Israel’s well-known chefs. At the grand opening of his Tel Aviv restaurant—a non-certified establishment—he introduced a signature dish: French toast made with butter and cream. The dish became wildly popular, drawing long lines, including many traditional Jews who kept kosher. “What could be wrong with French toast?” they thought.
But behind the scenes, the story was very different. On opening day, a cook accidentally poured meat steak drippings over the French toast. Instead of discarding the dish, the kitchen staff served it. Diners loved it, and from then on, the staff began intentionally adding meat juices to the dairy dessert to enhance its flavor.
Kosher-observant customers had no idea they were eating a mix of meat and dairy, something strictly forbidden by Jewish law. And in an establishment without a kosher supervisor, there’s no one to ensure proper standards or to hold accountable when violations occur.
Understanding the Highest Standard of Kosher Slaughter
In Jewish law, an animal is considered treif (non-kosher) if it has a physical defect or a potentially life-threatening condition. Naturally, this also makes it less healthy for consumption. That means kosher meat—and even more so glatt kosher meat—is not only spiritually cleaner but may also be physically healthier.
One of the key inspections in the kosher slaughter process takes place immediately after the animal is slaughtered: the lungs are examined for defects. If a puncture or hole is found, the animal is declared treif and its meat is not kosher.
Sometimes, the lung has thin fibrous strands called lesions, which may or may not conceal a puncture underneath. These lesions must be carefully examined and, in some cases, manually removed and tested. If the lung cannot be verified as intact, the animal is disqualified.
Glatt kosher meat (from the Yiddish word “glatt,” meaning “smooth”) refers to meat from an animal whose lungs were completely free of lesions. It is the highest standard of kosher meat.
One of the deeper ideas behind keeping kosher is the development of inner refinement and self-control. A kosher lifestyle demands conscious restraint. Before putting anything into our mouths, we must pause, check, and think. And it turns out that this kind of restraint comes with significant benefits.
One famous study that highlights this was the “Marshmallow Test,” conducted by psychologist Walter Mischel in 1970. In the experiment, young children were each offered a marshmallow and told that if they could resist eating it for a set period of time, they would receive two marshmallows instead. Each child was then left alone for twenty minutes while being observed on camera.
The results were striking: only about one-third of the children were able to wait the full time, while the rest gave in to temptation. But the real insight came years later, when researchers followed up to see how these children had fared in life.
Those who had successfully delayed gratification turned out to do significantly better across the board. They achieved more in their careers, had better mental health and family stability, and reported higher levels of overall happiness compared to their peers who had not been able to wait.
In the same way, keeping kosher is about more than just food—it’s about training the soul. It’s a daily opportunity to build the muscle of restraint, to strengthen our capacity for patience, discipline, and spiritual awareness.
The Torah provides clear criteria for identifying kosher animals and, in some cases, even lists specific species by name. These signs are not arbitrary. They reflect a consistent Torah law that has been preserved for generations.
Land Animals: Two Required Signs
For an animal to be kosher, it must meet both of the following conditions:
The Torah makes a remarkable claim: every land animal in the world either has both signs or neither. Only four animals have one sign but not the other—and the Torah names them specifically to avoid confusion: the camel, the hyrax, the hare, and the pig. All are non-kosher.
Fish: Fins and Scales
A kosher fish must have both fins and scales. This rules out shellfish, crustaceans, and all forms of seafood labeled as “non-fish” (shrimp, crab, lobster, etc.).
A fascinating halachic principle emerges from this category: “Any fish that has scales will also have fins, but some that have fins may not have scales” (Niddah 51b).
In other words, if a fish has scales, it is kosher, because it is guaranteed to have fins as well. This is a testable scientific claim. And as of today, over 34,300 species of fish have been discovered, and not one contradicts this rule. Only the Creator of all marine life could have embedded such a universal law into the text of the Torah thousands of years ago.
Birds: Tradition Is the Guide
Unlike land animals and fish, the Torah doesn’t give specific physical signs to identify kosher birds. Instead, it lists the names of non-kosher species. Over time, the precise identification of many biblical bird names was lost. Therefore, in modern practice, only birds with a clear and continuous tradition of being kosher are permitted.
Understanding the Highest Standard of Kosher Slaughter
In Jewish law, an animal is considered treif (non-kosher) if it has a physical defect or a potentially life-threatening condition. Naturally, this also makes it less healthy for consumption. That means kosher meat—and even more so glatt kosher meat—is not only spiritually cleaner but may also be physically healthier.
One of the key inspections in the kosher slaughter process takes place immediately after the animal is slaughtered: the lungs are examined for defects. If a puncture or hole is found, the animal is declared treif and its meat is not kosher.
Sometimes, the lung has thin fibrous strands called lesions, which may or may not conceal a puncture underneath. These lesions must be carefully examined and, in some cases, manually removed and tested. If the lung cannot be verified as intact, the animal is disqualified.
Glatt kosher meat (from the Yiddish word “glatt,” meaning “smooth”) refers to meat from an animal whose lungs were completely free of lesions. It is the highest standard of kosher meat.
According to halacha (Jewish law), “One witness is deemed credible with regard to prohibitions” (Gittin 2a). In other words, when it comes to what is permitted or forbidden to eat, we can rely on the word of someone who is knowledgeable and God-fearing. That’s exactly the role of the kosher supervisor (known as the mashgiach): a trained and trusted individual who verifies that the food is indeed kosher.
The kosher supervisor oversees every aspect of food preparation at a restaurant or food establishment, from checking the kosher status of ingredients to ensuring that all laws of kosher are observed throughout the preparation and cooking process.
The Hidden Risks of Dining Without Certification
Even if the food looks kosher and there’s a picture of a rabbi on the wall, without kosher supervision, you never really know what’s going on in the kitchen.
Take, for example, a story shared by one of Israel’s well-known chefs. At the grand opening of his Tel Aviv restaurant—a non-certified establishment—he introduced a signature dish: French toast made with butter and cream. The dish became wildly popular, drawing long lines, including many traditional Jews who kept kosher. “What could be wrong with French toast?” they thought.
But behind the scenes, the story was very different. On opening day, a cook accidentally poured meat steak drippings over the French toast. Instead of discarding the dish, the kitchen staff served it. Diners loved it, and from then on, the staff began intentionally adding meat juices to the dairy dessert to enhance its flavor.
Kosher-observant customers had no idea they were eating a mix of meat and dairy, something strictly forbidden by Jewish law. And in an establishment without a kosher supervisor, there’s no one to ensure proper standards or to hold accountable when violations occur.
Yosef Wallis had it all. Not yet thirty, he was already a rising star in international business. He traded aircraft parts and global commodities, lived in a luxurious villa in Israel’s Sharon region, and had a thriving family, successful children, and more than enough money. Life was good. His social standing was enviable, and there were no clouds on the horizon.
Which is why, when he showed up one day wearing a large kippah, his friends were stunned.
It hadn’t happened overnight. The turning point came after he attended a three-day seminar on Judaism packed with lectures, debates, and soul-searching questions. Against all the odds, something changed deep within him.
On the way home, his wife asked why he was still wearing the yarmulke. “The rabbis aren’t around anymore,” she said gently. “You can take it off.” But for Yosef, the decision was already made. He had crossed a line back into the embrace of Judaism.
“What got me to the seminar in the first place,” says Yosef, now Rabbi Wallis, “was one question I couldn’t answer.” And with that, he tells the story that changed everything:
His grandfather, Rabbi Shraga Feivel Winkler, was a prisoner in a Nazi concentration camp during World War II. Just hours before liberation, as the German soldiers were packing to flee, the prisoners sensed freedom in the air. Hope was tangible. The nightmare was almost over.
And then, just before their escape, the soldiers pulled a final, vicious stunt. They took Yosef’s grandfather, known as the rabbi of the camp, and forced him to sit in the middle of the yard. One soldier held a piece of non-kosher meat in one hand and a loaded gun in the other.
“Eat the meat and save your life,” the soldier barked.
The other prisoners stood frozen. Was this really happening, just moments before freedom?
But the rabbi didn’t hesitate. He refused to eat the non-kosher meat.
A single gunshot shattered the silence and ended his life. The meat dropped to the dusty ground, untouched, and his soul ascended to join the ranks of the holy martyrs.
“Years later,” Rabbi Wallis continues, “I found myself far from observance.” One day, he walked into a non-kosher deli and suddenly remembered the story. “My grandfather gave his life to avoid eating this, and I’m buying it for my family?” The question burned inside him. “How can I not keep kosher when my grandfather literally died for it?”
Did he ever think his grandfather was wrong?
“Never,” he says. “But I didn’t think his actions would force me to change. Yet once I realized that Judaism is the truth, there was no turning back. I had status, wealth, everything. But when you find truth, doubt disappears.”
Today, Rabbi Wallis leads Arachim, an organization dedicated to helping Jews reconnect with their heritage.
And so, a moment of self-sacrifice in a Nazi camp, mere hours before liberation, gave rise to generations of Jews who found their way back home. All because of a single piece of nonkosher meat that fell to the floor and was never eaten.
