Unlabeled GMOs in cheese?

Cheese is a staple in many diets, enjoyed for its rich flavor, versatility, and high-quality protein and fat content. But what if the cheese you’re eating contains a genetically modified ingredient that isn’t labeled? What if a pharmaceutical giant developed that ingredient? These are questions more consumers should ask, especially as genetically engineered chymosin, a lab-created version of rennet, is now used in around 90% of U.S. cheese production.

Chymosin is the enzyme that separates curds from whey, an essential step in cheesemaking. Traditionally, rennet was sourced from calf stomachs, but to cut costs and streamline production, food manufacturers have turned to genetically modified chymosin.^[1] What makes this even more concerning is that it is not required to be labeled as a GMO ingredient. This means that unless you actively seek organic or traditional cheese, you are likely consuming a genetically engineered product without knowing it.

The Rise of Genetically Engineered Chymosin

Historically, cheese was made using animal rennet, an enzyme naturally present in the stomachs of young calves, helping them digest milk. For centuries, cheesemakers relied on this natural enzyme to coagulate milk and form cheese. However, with the rise of industrial food production, sourcing traditional animal rennet became less practical for mass production.^[2]

In the 1990s, the biotech industry introduced a genetically engineered version of chymosin. By inserting calf genes into bacteria, fungi, or yeast, scientists were able to create lab-grown chymosin without relying on livestock. This new form of microbial rennet was approved by the FDA in 1990, and since then, it has become the dominant method for producing cheese in the U.S.^[3]

Pfizer’s Role in GMO Chymosin Production

Most people associate Pfizer with pharmaceuticals, but the company has deep ties to the food industry as well. Pfizer was directly involved in the early commercialization of genetically engineered chymosin through its subsidiary, Gist-Brocades. Today, the manufacturing of microbial and genetically modified rennet has been taken over by companies like DSM, but Pfizer played a key role in making GMO chymosin the standard in the cheese industry.

This raises an important question: if a pharmaceutical company helped introduce a genetically modified ingredient into the food supply without labeling requirements, what else could be hidden in our food?

Why GMO Chymosin Isn’t Labeled

One of the most concerning aspects of GMO chymosin is that it does not have to be disclosed on food labels. While many consumers assume that GMOs are required to be labeled, there are loopholes in U.S. food regulations that allow for genetically engineered processing aids to go undisclosed.

Unlike genetically modified crops such as corn and soy, which are sometimes labeled as GMOs, enzymes like chymosin fall under a different category. Because it is considered a “processing aid” rather than a primary food ingredient, food manufacturers are not required to list it as genetically engineered. This means that even if you are consciously trying to avoid GMOs, you could still be consuming them without knowing it.

Health Implications of Consuming GMO Cheese

For those who prioritize cellular health, avoiding genetically modified ingredients is a crucial part of supporting overall wellness. While research on the long-term effects of genetically modified chymosin is limited, there are several concerns to consider:

• Lack of Transparency: If one genetically modified ingredient is hidden in food, it raises questions about what other undisclosed additives and processing aids are being used.
• Microbial Contamination Risks: Lab-produced enzymes rely on genetically modified bacteria, fungi, or yeast, raising concerns about potential contaminants that may not be properly removed during processing.
• Impact on Gut Health: Many people experience digestive issues from processed dairy products. While chymosin itself is an enzyme, the broader impact of genetically engineered proteins on gut microbiota is not well studied.

How to Avoid GMO Cheese

If you are concerned about consuming genetically engineered chymosin, there are several ways to ensure that your cheese is free from GMO ingredients.

• Choose organic cheese. Organic certification prohibits the use of genetically engineered enzymes, making USDA-certified organic cheese one of the safest options.
• Look for cheese made with traditional animal rennet. Some cheese brands still use traditional calf rennet instead of genetically modified chymosin. Check labels carefully or contact the manufacturer to confirm.
• Seek out non-GMO microbial rennet. Some cheesemakers use microbial rennet that is not genetically modified, offering a GMO-free alternative.
• Support artisanal cheesemakers. Many smaller cheesemakers are transparent about their processes and avoid the use of genetically engineered ingredients.

Final Thoughts

When it comes to optimizing health at the cellular level, transparency in food production is just as important as choosing nutrient-dense foods. The widespread use of genetically modified chymosin in cheese is a prime example of how the food industry operates with minimal disclosure, allowing hidden GMOs to make their way into everyday products. While it may not be possible to eliminate all GMOs from the diet, making informed choices about what you consume can help reduce unnecessary exposure to genetically engineered ingredients. Opting for organic cheese, researching brands, and demanding better labeling practices are all steps toward reclaiming control over your food choices.

1. Nicosia, Fabrizio Domenico, et al. “Plant Milk-Clotting Enzymes for Cheesemaking.” Foods, vol. 11, no. 6, Mar. 2022, p. 871.
2. History of Cheese.” NHCC Museum and Green County Welcome Center, https://nhccmuseum.org/history-of-cheese/. Accessed 12 Feb. 2025.
3. 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.