Shelf life can be defined in several ways, and may be much confused by the different labels that are attached to foods like “use by,” “best by” or “best if used by.” Generally, shelf life refers to the time a prepared food item will remain fresh, remain healthy to eat, and keep its freshest taste. Eating foods with expired shelf lives is definitely not recommended, since shelf life can be an indication that food will go bad after a certain time.

Confusion about shelf life can be attributed to the recent label on many foods in grocery stores that recommend a food is “best by” a certain date. This means the store or the manufacturer guarantees the food should still taste its freshest if the food is consumed before the best by date. This does not always mean that the food is bad after this date. In fact, manufacturers tend to want to undershoot the mark of safe food expiration dates so that people don’t get food that is stale or just simply doesn’t taste fresh.

For instance stale bread, provided it isn’t moldy, may be safe to consume. If you’ve ever opened a package of graham crackers, you know that an open package means the crackers will be soft within a few hours. This doesn’t mean they’re unsafe, and you haven’t exceeded their shelf life by eating them. It just means they’ve quickly gone stale when exposed to air. You should take "use by" labels more seriously, since these mean the food may potentially be unsafe to eat after the date specified.

Some people are concerned when certain foods have a long “life” on the shelf, since this may indicate a high amount of preservatives in the food. Preservatives do tend to extend food’s ability to last, but some preservatives may be quite natural and safe to consume. Most people make jokes about the shelf life of foods like Twinkies®, but in actuality, these snack cakes won’t last forever on a shelf. Like all foods, they do go bad past a certain date.

Shelf life can also apply to medications, both over the counter and prescription, and you should definitely adhere to expiration dates on medications. Some drugs can actually become stronger over time, while others become inactive. This means using a medication past its shelf life hazards either the risk of the medication not working or being toxic. If you’re in doubt, you can ask your pharmacist if a medication you plan to use has just expired. Some medications will remain stable past their expiration date.

With both food and medication, expiration dates are important to note. You’ll find that products that are vacuum-sealed or are canned tend to have the longest shelf lives. Fresh products like breads, crackers, vegetables, dairy items, and raw meat usually last for the least amount of time. The old adage about food safety is a good one to adhere to: When in doubt, throw it out.