Cheese has long been considered a nutrient-dense food, providing essential fats, proteins, and bioavailable vitamins. But for many people, a hidden genetically modified ingredient is making its way into their favorite cheeses without any disclosure.
An estimated 90% of U.S. cheese is made with genetically engineered chymosin, an enzyme that separates curds from whey in cheesemaking. Unlike traditional rennet, which is sourced from calves, GMO chymosin is created using genetically modified bacteria, fungi, or yeast. Even more concerning is that this ingredient does not have to be labeled as genetically modified, meaning that most people consuming cheese are unaware that they are eating a lab-produced product.
The Shift From Traditional Rennet to GMO Chymosin
Historically, cheese has been made using animal rennet, an enzyme that aids in milk digestion in young calves. Cheesemakers relied on this enzyme for centuries to naturally coagulate milk and form cheese. However, as the dairy industry expanded, sourcing rennet from calves became impractical for large-scale production.[1-2]
To meet growing demand, the food industry turned to microbial rennet, and by the 1990s, genetic engineering made it possible to produce chymosin without animal sources. By inserting calf genes into genetically modified microorganisms, scientists created a lab-based chymosin enzyme, quickly becoming the dominant form used in the U.S.[3]
Pfizer’s Role in Bringing GMO Chymosin to Market
While many consumers are familiar with Pfizer as a pharmaceutical company, few realize it played a key role in introducing genetically engineered chymosin to the cheese industry. Through its subsidiary, Gist-Brocades, Pfizer was instrumental in developing and commercializing microbial rennet, which has now become the standard in non-organic cheese production.
This raises significant concerns about transparency in the food industry. What other undisclosed biotech innovations are shaping the food supply if genetically engineered ingredients can be introduced without labeling requirements?
Why GMO Chymosin Isn’t Labeled
Despite growing consumer demand for GMO transparency, genetically modified chymosin remains exempt from labeling laws. This is because the FDA classifies it as a “processing aid” rather than a primary food ingredient. As a result, cheese manufacturers are not required to disclose its presence, making it nearly impossible for consumers to identify which cheeses contain GMO-derived rennet.
How to Avoid Genetically Engineered Chymosin
For those who prioritize whole, natural foods, avoiding genetically modified ingredients in cheese requires careful label reading and brand research. Some of the best ways to ensure a dairy product is free from GMO chymosin include:
- Choosing certified organic cheese
- Looking for cheese made with traditional animal rennet
- Seeking out brands that use non-GMO microbial rennet
- Supporting small-scale artisanal cheesemakers
Final Thoughts
The lack of transparency surrounding genetically engineered chymosin is yet another example of how biotech-driven food production often prioritizes efficiency over consumer awareness. While the long-term impact of GMO chymosin on human health is not fully understood, making informed decisions about food choices can help minimize unnecessary exposure to hidden genetically modified ingredients.
References:
- Nicosia, Fabrizio Domenico, et al. “Plant Milk-Clotting Enzymes for Cheesemaking.” Foods, vol. 11, no. 6, Mar. 2022, p. 871.
- History of Cheese.” NHCC Museum and Green County Welcome Center, https://nhccmuseum.org/history-of-cheese/. Accessed 12 Feb. 2025.
- Genetic Engineering Has Been Applied to Cheese Making: No Reason to Be Cheesed Off.” Office for Science and Society, https://www.mcgill.ca/oss/article/health-and-nutrition-technology/genetic-engineering-has-been-applied-cheese-making-no-reason-be-cheesed. Accessed 12 Feb. 2025.