Many consumers are needlessly throwing out thousands of kilograms of food every year because they falsely believe that "best before" dates on food packages are an indication of food safety, a new study has found.

Research published Wednesday by Harvard Law School and the Natural Resources Defense Council contends that the dates printed on packaged foods only serve to confuse consumers and compel many to throw out food that hasn't gone bad at all.

Here in Canada, a report last year from the Value Chain Management Centre in Guelph, Ont., estimated that about $27 billion worth of food is wasted every year on its way to Canadian dinner tables. And about half of that waste occurs in the home.

The problem of food waste has many causes, but the study authors say that one part problem is that there are no binding standards on best before date labelling. That leaves it to food manufacturers to decide on their own how to set best before dates and what kind of phrasing to use.

Dana Gunders, a staff scientist with the NRDC's food and agriculture program, says the current food dating system "is not a system at all. It's a mess."

And she says that mess is leading to perfectly good food going to waste.

"Phrases like 'sell by', 'use by', and 'best before' are poorly regulated, misinterpreted and lead to a false confidence in food safety," she said in a statement. "It is time for a well-intended but wildly ineffective food date labelling system to get a makeover."

As Gunders and her co-authors explain, there are two main categories of food date labelling: those intended to communicate to food retailers, and those for consumers.

"Sell by" dates are for retailers to help with stock control, and are a suggestion about when the retailer should no longer sell products in order to ensure they still have good shelf life after consumers purchase them. They are not meant to indicate the food is bad on that date. "Best before" and "use by" dates, on the other hand, are intended for consumers.

In Canada, the federal government requires best before dates on foods that will keep fresh for less than 90 days; they are not required on food with a longer shelf life. Manufacturers are free to add best before dates to these products, though.

As the study authors point out, the dates on shelf-stable foods, like canned peaches, are often just a manufacturer's estimate of when the food will no longer be at "peak quality" - meaning it has the same texture and colour as when it left the processing facility, and not an indication of when the food will become unsafe.

With few regulations on how these dates are determined, the study found that for the vast majority of food products, manufacturers are free to determine date shelf life according to their own methods. The result, say the authors, is confusion among consumers who assume the dates are actually expiry dates.

Registered dietician Rosie Schwartz agrees with the study authors that what's needed in both the U.S. and Canada is a standardized labelling system that offers clear information.

"I think this is a really important issue People are really confused by Best Before dates," she told

"We need to know: is that the date you've chosen because of safety, or because of quality and it's just not going to taste as great?... It has to be separated in terms of safety and quality because those are two different things."

Confusion over best before dates are causing two problems, Schwartz believes: not only are shoppers needlessly throwing out food that's still safe to eat, they are also keeping foods they should throw out, because they are relying too strictly on the dates.

Such dates apply only to unopened foods, Schwartz says. Once a product is opened, it usually needs to be eaten within a few days. But some consumers mistakenly believe products are good until their best before dates, even if they open them weeks before.

The authors of this study recommend a solution for this problem: they'd like to see labels that offer an indication of shelf life after opening, using phrasing such as "Best within XX days of opening".

They also recommend a number of other changes, including:

  • Make "sell by" dates that are meant for retailers be invisible to the consumer. Only the dates that are useful to the consumer should be visible.
  • Remove quality-based dates on non-perishable, shelf-stable products altogether and replace them with dates that indicate shelf life after opening.
  • Use a more easily understandable date label system that uses consistent, unambiguous language and clearly differentiates between safety- and quality-based dates.
  • Ensure date labels are clearly and predictably located on packages, similar to the "nutrition facts" panel.
  • Employ more transparent methods for selecting dates: Create a set of best practices that manufacturers and retailers can use to determine date labels for products.
  • Including "freeze by" dates, where applicable. Such labels would help raise consumer awareness of the benefits of freezing foods and the abundance of food products that can be successfully frozen in order to extend shelf life.

Schwartz notes though that while improvements to Best Before dates are badly needed, consumers shouldn't fully rely on them. That's because the dates assume that food distributors and retailers have ensured they kept the foods at the right temperatures. Even milk with a best before date of three weeks from now can still go off if it's allowed to sit outside a refrigerator for too long.

The vast majority of food poisonings are due to harmful bacteria, such as salmonella and E. coli, entering foods, not from eating expired or spoiled foods. But Schwartz she doesn't agree with those who say that a little bit of mould isn't harmful.

Schwartz notes that food mould can release a toxin called mycotoxins, and there's been "quite a bit of research" showing that these toxins can raised the risk for certain types of cancer, including liver cancer.

Such moulds can travel through soft or liquid foods, bringing the toxins with them, which is why it's important to throw mouldy food out. With hard cheeses or hard produce such as an onion, it's safe to cut away the mould, she says, but that's not the case with softer foods.

"A tomato with a little mould on it should be thrown out. A container of yogourt with mould should be tossed," she says. "If I see mould on any part of a bread, I throw the whole thing out."

"A one-time exposure in a small amount is not going to make you sick, but the repeated exposure has been linked to cancer."