The process of canning preserves food by sealing it in an airtight container and subjecting it to heat to kill spoilage microorganisms. This technique ensures a safe, shelf-stable, and affordable food supply. Despite its benefits, public concern has arisen regarding the safety of commercially canned products and their potential to increase cancer risk. This anxiety centers on chemicals originating from two distinct sources: the protective lining of the can itself and certain chemical additives used within the food product. Understanding the science behind these concerns offers a clearer picture of the overall risk profile.
The Primary Concern: Bisphenol A in Linings
The most widely discussed chemical concern associated with canned food packaging is Bisphenol A, commonly known as BPA. This industrial chemical is a building block for epoxy resins used to create the protective interior lining of most metal cans. The resin lining prevents the metal from corroding or reacting with the food, which maintains both the food’s quality and the can’s integrity.
BPA is a recognized endocrine-disrupting chemical because its molecular structure mimics the body’s natural hormones, specifically estrogen. This interference with the endocrine system is the basis for theories linking it to potential health issues, including hormone-related cancers like breast and prostate cancer. Exposure occurs when trace amounts of unreacted BPA leach from the epoxy coating into the food contents. This migration is accelerated when the food is acidic, such as tomatoes, or when the can is exposed to elevated temperatures.
Growing consumer concern has driven significant change across the packaging industry. Today, over 90 to 95 percent of food cans in some major markets no longer use BPA-based linings, a shift driven by market demand. Manufacturers have moved toward alternative internal coatings, often utilizing materials like acrylic, polyester, or olefin polymers. However, the safety of these “BPA-free” alternatives is still under ongoing review, as some replacements have not been as extensively studied as BPA itself.
Chemical Additives and the Role of Preservatives
Separate from the can’s lining, certain canned foods contain chemical additives that have also come under scrutiny. This concern primarily focuses on nitrates and nitrites, compounds used as preservatives and color fixatives, particularly in processed meats found in canned forms. These chemicals are highly effective at preventing the growth of harmful bacteria, such as Clostridium botulinum, which causes botulism.
The risk associated with these preservatives emerges from their conversion into nitrosamines. Nitrates convert to nitrites, and under high-heat conditions or the acidic environment of the human stomach, these nitrites react with amines present in protein-rich meat. This reaction forms N-nitroso compounds, which include nitrosamines, many of which are considered probable human carcinogens.
To mitigate this conversion, regulatory guidelines often require manufacturers to include blocking agents like sodium ascorbate, a form of Vitamin C, in the curing process. These antioxidants interfere with the chemical reaction that forms nitrosamines, redirecting the nitrite to a less harmful compound. While nitrates are also found naturally in vegetables like spinach and celery, the cancer risk is not associated with vegetable consumption because the presence of Vitamin C inhibits nitrosamine formation.
Scientific Verdict and Regulatory Stance
The scientific consensus regarding cancer risk from canned food involves two distinct evaluations: the packaging and the contents. For the food content itself, the International Agency for Research on Cancer (IARC) has classified processed meat as Group 1, meaning it is carcinogenic to humans; canned meat falls under this classification. This determination is based on sufficient evidence linking its consumption to an increased risk of colorectal cancer, primarily due to the formation of N-nitroso compounds.
Regarding the packaging chemical BPA, regulatory bodies like the European Food Safety Authority (EFSA) and the U.S. Food and Drug Administration (FDA) maintain that current exposure levels are below safety thresholds. The EFSA has established a Tolerable Daily Intake (TDI) of 4 micrograms per kilogram of body weight per day, a level considered safe for daily, lifelong exposure. The FDA also supports the safety of BPA in can linings at the low levels found in food, though they removed it from infant formula cans and baby bottles as a precautionary measure.
Consumers can minimize potential exposure by making informed dietary choices. Prioritizing fresh or frozen foods when possible remains the most direct way to avoid packaging chemicals. When choosing canned goods, consumers can look for explicit “BPA-Free” labeling, although this does not guarantee the safety of the replacement lining. Limiting the consumption of canned processed meats is also prudent, given the IARC’s classification. Understanding the low-level exposure risks and regulatory limits allows consumers to balance the convenience of canned goods with a focus on a diverse diet.