Most cheese is vegetarian, but not all of it. The key factor is rennet, an enzyme used to curdle milk during cheesemaking. Traditional rennet comes from the stomach lining of young calves, which makes any cheese produced with it non-vegetarian. However, roughly 90% of commercial cheese made in the United States now uses lab-produced alternatives that contain no animal tissue.
Why Some Cheese Isn’t Vegetarian
Thousands of years ago, cheesemakers discovered that tissue from a ruminant’s stomach could coagulate milk, separating solid curds from liquid whey. The active enzyme in that stomach tissue, called chymosin, became the standard way to make cheese for centuries. Because extracting traditional rennet requires slaughtering a calf, cheese made this way is not vegetarian by most definitions.
Many classic European cheeses still use animal rennet today. Parmigiano Reggiano, Stilton, traditional English cheddar, Comté, and Manchego are common examples. For some of these, animal rennet is actually required by the cheese’s protected designation of origin, meaning producers can’t substitute alternatives and still use the name. If you’re buying imported or artisan cheese, animal rennet is more likely than with mass-produced brands.
Cheeses That Are Always Vegetarian
Some cheeses skip rennet entirely. These “acid-set” cheeses use heat and an acid like citric acid or lemon juice to curdle the milk instead. Paneer, the Indian fresh cheese, is a classic example: milk is brought to a boil and citric acid is stirred in, causing it to separate into curds without any enzyme at all. Ricotta, queso blanco, and cream cheese are other common acid-set varieties. These are inherently vegetarian regardless of brand.
Three Types of Vegetarian Rennet
For cheeses that do need rennet, several animal-free options exist.
- Plant rennet uses the natural coagulating properties of thistle, nettles, dried caper leaves, or artichokes. This method has its own long history, particularly in Portuguese and Spanish cheesemaking.
- Microbial rennet comes from certain molds, yeasts, or fungi that produce enzymes capable of curdling milk.
- Fermentation-produced chymosin (FPC) is the most widely used alternative. Scientists insert the gene responsible for calf chymosin into bacteria, fungi, or yeast, which then produce the identical enzyme through fermentation. No animal is involved in the process. By 2012, an estimated 90% of all commercial cheese in the U.S. was made with FPC.
Major enzyme manufacturers market their FPC products as “vegetarian” and “suitable for vegetarian cheeses.” The resulting cheese is considered indistinguishable in taste and texture from cheese made with calf rennet. That said, because FPC involves genetic engineering, some vegetarians who avoid GMO-derived ingredients may have reservations. Most vegetarian organizations accept FPC as vegetarian, but it’s a personal line to draw.
How to Tell What’s in Your Cheese
Figuring out whether a specific cheese uses animal rennet can be frustrating. In the United States, there is no legal requirement to specify the type of rennet on a label. Ingredients lists often say simply “enzymes,” which tells you nothing about the source. The UK is the only country that requires vegetarian cheeses to carry a “V” label, making identification much simpler there.
A few label clues can help. If the ingredients list “vegetable rennet,” that’s a straightforward indicator of a plant-based coagulant. “Microbial rennet” or “non-animal enzymes” also signal a vegetarian product. Some brands label their rennet as “vegetarian rennet,” which usually refers to FPC. If the label just says “rennet” or “enzymes” with no qualifier, you can’t be sure without contacting the manufacturer directly.
Many larger U.S. cheese brands do use FPC and will confirm this on their websites or through customer service. Smaller artisan producers and European imports are more likely to use traditional animal rennet, especially for aged hard cheeses.
Ordering Cheese at Restaurants
Restaurants rarely know what type of rennet is in their cheese. Surveys of major restaurant chains have found that cheeses used in pizzas, sandwiches, and other dishes sometimes contain animal rennet, and staff typically can’t tell you one way or the other. Cheddar, Jack, and mozzarella at chain restaurants may or may not be made with animal-derived enzymes.
If this matters to you, your practical options are limited when eating out. You can ask, but expect vague answers. Dishes made with inherently vegetarian cheeses like ricotta, cream cheese, or paneer are safer bets. For pizza, some chains have confirmed their cheese contains animal rennet, which means even a “vegetarian” pizza with vegetables isn’t technically vegetarian. At home, you have far more control: check the label, look up the brand online, or choose one of the many products now explicitly marketed as vegetarian-friendly.