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From grocery stores to our medicine cabinets, dates stamped on products carry a subtle authority. These "best before" or "expiration" dates guide our consumption, influence our purchasing decisions, and, in some cases, shape the ingredients list on our favourite food products. But what do these dates really mean? Who decides them, and how are they determined?

In Canada, serve distinct purposes. 鈥淏est before鈥� dates, found on perishable foods like dairy and bread, indicate the period during which the product is expected to maintain optimal quality and freshness. However, consuming these items shortly after the date usually pose no health risks. On the other hand, expiration dates, often found on medications or fortified foods like baby formula, mark the point after which the product may lose its effectiveness or safety. These dates demand stricter adherence. But determining these timelines is a balancing act, with known players like safety and quality, and more elusive ones like economics and access.

The Science Behind the Stamps

The process of assigning a "best before" date involves testing how long a product maintains its intended flavor, texture, and safety under controlled conditions. It is the to determine the durability of their products and to label them accurately.

Food preservation techniques, like refrigeration, pasteurization, or the addition of preservatives, can significantly extend shelf life. Take , for example, which started as a fermented fish sauce, 鈥渒e-tsiup,鈥� in China. As this sauce made its way into Europe and eventually America, the tomato replaced fish as the main ingredient, preserving the salty and umami flavor profile while alsomaking it cheaper and more accessible. Without the natural preservation from fermentation, manufacturers quickly found that the sauce wouldn鈥檛 last very long on the shelves. So, with a whole lot of salt and a whole lot of sugar, ketchup evolved into the tangy, shelf-stable condiment we know today thanks to the motivation to preserve.

For medications, expiration dates can carry life-or-death weight. Prescriptions are written to manage a vast array of bodily processes, including anything from hormones and pain to fluid balance and blood sugar levels. Take chemotherapies, for example, where the dosing and potency are bounded by very narrow windows. It is no surprise that the attached expiration dates bear a huge responsibility. Drugs go through a lengthy process to make it from the bench to the market, including pre-clinical studies and multiple phases of clinical trials to establish maximum tolerable doses, safety, and effectiveness. Even after drugs are in pharmacies and our bathroom cabinets, there is a whole of that seeks to evaluate continued safety of medications when taken in the real world. Expiration dates are decided by manufacturers right from the get-go: in the pre-market stage.

Stamping a date on these items requires a balancing act too. From an ethics and access perspective, there is argument for a potential benefit lost if the dates are too restrictive. When teaching first aid, I鈥檓 often asked about expiration dates in the case of medications used in emergency contexts: isn鈥檛 using somethingbetter than nothing? has shown that EpiPens, for example, can retain some effectiveness after their expiration date, so in emergency situations, if the medication has no discolouration or precipitates, the benefit of injecting a suboptimal epinephrine dose is better than providing no treatment at all. found that in the realm of first aid, many medications retained the active drug well past expiration dates, with minimal harmful degradation byproducts, thus justifying less-than-perfect medications when there is no other choice.

Table summarizing the findings from Charlton et al. 2025 on the use of expired resuscitation medications for life-threatening first aid conditions

To be clear, many medications can and will be harmful if taken beyond their diligently researched expiration dates. As such, these dates often err on the side of caution, ensuring potency and safety. On a population scale, when resources are scarce and there are drug shortages, there are to ensure access.

Politics of Preservation

Sometimes, these dates are less about science and more about policy. In Montana, a is ostensibly a quality-control measure but effectively limits imports. State law imposes a strict from the date of pasteurization, after which the milk must be tossed, even if it鈥檚 safe to drink. Most other states have a much longer time period or a 鈥渂est before鈥� date. Because the 12-day window is so short, it鈥檚 nearly impossible for neighboring states to transport their dairy products into Montana quickly enough. This protects local producers, but also creates a de facto monopoly on the market that drives food waste. In some cases, manufacturers will even retrieve this 鈥渆xpired鈥� milk to turn it into other dairy products, because it is still perfectly fine. The consequence of this 鈥渟ell-by鈥� date? Increased food waste and higher costs for consumers.

鈥淏est Before鈥� Does Not Mean 鈥淏ad After鈥�

The reality is that many products remain usable long after their best-before dates. That carton of milk might be perfectly fine a few days later, especially if it鈥檚 been stored properly. Bread can often be revived with a quick toast. That said, a fine balance exists. Mark dates too early, and food waste skyrockets; too late, and the risk of safety issues arise. It鈥檚 a decision shaped by public health, legal, and environmental considerations.

From the Montana dairy industry to Heinz ketchup to EpiPens, our relationship with shelf-life reflects how often our products and their labelling are defined by human invention and consumption. The next time you check a date on your groceries, consider that the product is 鈥渂est before鈥�, but not necessarily 鈥渂ad after鈥�.

Cat is a medical student at 51吃瓜网, where she previously completed a BSc in Anatomy & Cell Biology and MSc in Public Health. Her research experience spans molecular genetics, anatomy pedagogy, and health policy.