Everyone approaches safe food handling a little differently. Some people rely on the smell test; others are fastidious about washing their hands.

But according to a new survey, consumers waste food—a lot of food—because they don't understand the meaning of the expiration dates on the food labels.

The online survey, led by researchers at Johns Hopkins Center for a Livable Future and published in the journal Waste Management, polled 1029 respondents about their knowledge of food labels that use terms like “best if used by,” “sell by,” or “use by.” Roughly 84 percent said they opted to discard food on or near the so-called expiration dates at least occasionally, while 37 percent said they did it on a regular basis. Just over a third of those polled believed such food labels—often found on packaged dry food as well as bread and canned goods—were federally regulated, which they aren’t.

The survey indicates some confusion over food labeling. Typically, “best by” and “sell by” labels are meant to indicate when a food might begin to experience diminished freshness or quality, not an expiration date by which it could spoil or become a potential source of food-borne illness. By discarding these foods prematurely, researchers say, consumers are contributing to a food waste problem. The U.S. Department of Agriculture estimates that up to 31 percent of consumable food is wasted at both the retail and consumer levels.

Shoppers aren’t necessarily to blame. The labels often have no explicit explanation on packaging, leaving phrases like “best if used by” open to interpretation. Even individual states have different standards for items like milk, with some using a “sell by” date (with the milk typically good for five days after) and others sticking to a “use by” date.

Other pantry foods may have expiration dates but could conceivably last for years, like sugar, salt, and honey.

Newer food industry standards may clear up some of this confusion, with “use by” designated strictly for items where safety is a concern and other terms (including "best if used by") meant to denote quality. Taking the "use by" suggestion is especially important with deli meats and cheeses that can grow bacteria like Listeria in refrigerated environments. Until there’s a universally recognized standard, however, consumers are likely to remain uncertain about what these terms mean.

So what’s the best approach to interpreting food labels? For dry or non-perishable goods, dates are often a marker of quality, and you’re not likely to do yourself any harm by keeping the food around longer. Perishable goods should be discarded when their “use by” dates have arrived. But no matter what the package says, if doesn’t smell or look quite right, label it trash and go shopping.

[h/t ScienceDaily]