Leah Weinroth can only hope that her 11-year-old son Trey's obsession with expiration dates is a passing phase. If yogurt in the 43-year-old Bethesda, Md., writer's refrigerator is even a day past the date stamped on top, Trey "acts like it's poison" and throws it away. The same goes for packaged snacks.
"I tell him that kind of stuff doesn't really expire," she says. "But he just says it doesn't taste good if it's past its date."
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In this battle, mother knows best. Sell-by, use-by and best-by dates do not indicate whether a food is safe to eat, or even if is still tasty. But many people -- people far older than Trey -- believe that they do: Fifty-four percent of consumers say eating food past its sell-by or use-by date is a health risk, according to a U.S. Department of Agriculture report. A 2011 survey conducted by the Food Marketers Institute found that 91 percent of consumers occasionally discarded food past its sell-by date out of concern for the product's safety; 25 percent said they always did so.
Food waste has reached record levels. In the United States, an estimated 40 percent of food is thrown away. It happens at the farm, in transport, at supermarkets and in people's homes. Last year, a study estimated that the average American family of four wastes $1,560 worth of food annually.
Clearer expiration dates on food cannot alone solve the problem. But a new report, co-authored by the Natural Resources Defense Council and the Harvard Food Law and Policy Clinic, argues that revising the convoluted system of date labels would be a simple and straightforward way to slash food waste.
"What we have now is an ineffective, ridiculous system that isn't serving anyone," says Dana Gunders, a staff scientist at the NRDC and one of the authors of the report, which was unveiled earlier this month. "It costs manufacturers money. It costs consumers money. It leads us to throw food away unnecessarily."
Date labels first became popular in the 1970s. By that time, most Americans were buying, not growing, their own food, and they had little knowledge about the freshness or shelf life of store-bought products. To answer their concerns, many supermarkets voluntarily adopted so-called open-dating systems, which prominently stamped a month, day and year on food products. By 1973, 10 states had adopted laws or regulations that mandated open dates on certain kinds of foods. Congress considered action, as well. From 1973 to 1975, at least 10 bills were introduced to set standards for food dating. More recently, in 1999, Rep. Nita M. Lowey, D-N.Y. introduced the Freshness Disclosure Act, proposing a uniform federal system for date labels. Similar bills were introduced five times over the next decade, but none of them gained the momentum to pass into law.
The result is a patchwork of state regulations and laws. Forty-one states plus the District of Columbia require date labels on at least some food items. In Maryland, for example, only milk must have a date label, though the City of Baltimore also prohibits the sale of any perishable food past its expiration date. Virginia mandates dates on all dairy products and shellfish.
The District of Columbia's rules require dates on dairy products, meat, shellfish and eggs, plus perishable and potentially hazardous foods (ones that are time-sensitive or require temperature control for safety). Shoppers might still find date labels on all manner of products sold in Maryland and Virginia, because those items are also sold in places that require the labeling.
The labels are meant to empower consumers. Instead, they often puzzle and mislead them. "I am indeed confused by 'sell by' versus 'best by' versus a plain old expiration date," says Kelly Masley, 40, who lives in Arlington, Va. "My most frequent question with sell-by is, if the date has passed, how much longer do you have to eat it? How does that differ between sturdy things, like trail mix or beef jerky, versus chicken stock?"
The answer: It depends. Date labels come in a dizzying variety of forms. A production or pack date typically designates when a product was produced or put in its final package. Sell-by dates provide information to retailers about how long to display a product. Best-if-used-by typically indicates a date after which the food will no longer be at its highest quality -- as defined by the manufacturer. But the meaning of those terms varies from product to product, and even among manufacturers of the same products, because there is no industry agreement on definitions and on which labels should be applied to which foods.
Food-waste experts are hopeful that a growing public discussion on food waste will prompt regulatory action. Both the USDA and the FDA have the implicit authority to regulate date labels. Lowey says she plans to reintroduce her bill. "Date labels come up a lot when I talk about food waste," says Jonathan Bloom, the author of "American Wasteland: How America Throws Away Nearly Half of Its Food (And What We Can Do About It)."
But even the best system of rules and definitions can't always tell consumers when or whether to throw food away. "Having a date on a package of food is reassuring," says Bloom. "But you should always trust your senses before that arbitrary date on the package. Look, smell and, if it comes to it, taste it before you throw it away."
• Black is a former Washington Post Food section staffer. Follow her on Twitter @jane_black.