Seventy-eight-year-old Margaret Radomski told the Canadian Broadcasting Corp. she bought a can of lobster pate at a Walmart recently and was ill hours later. She later discovered the can had a best-before date of July 2011 -- 1 1/2 years before she bought it.
Radomski said she refused Walmart's offer of $50 compensation.
Felicia Fefer, a Walmart spokeswoman, said the company's policy is not to sell any products past their best before date.
"We take this issue very seriously," she told the CBC. "We regret this incident, and remain committed to ensuring outdated products are removed from our shelves."
Instead of compensation, Radomski told her story to the investigative arm of the CBC, which then visited 17 major grocery stores in the Vancouver, British Columbia, area and found one-third had outdated cans of fish and seafood on their shelves.
Cans of tuna and shrimp, labeled best before 2010 to 2012, were found mixed with cans labeled best before 2015, the CBC said.
Safeway public affairs manager Betty Kellsey said store shelves are checked weekly for out-of-date products.
Peter Clarke, the marketing director of Clover Leaf said manufacturers say canned tuna and seafood has an approximate shelf life of three years after packing, before the best before date kicks in. However, unless the can is damaged, Clarke said it is still safe to eat, indefinitely.
"This has nothing to do with product safety. We do this because consumers do not wish to purchase product that has passed its best-before date ... best-before does not imply bad after," Clark told the CBC.
Siyun Wang, a professor of food engineering at the University of British Columbia, said there is not enough data, so it's hard to judge.
After being contacted by the CBC, the Consumers' Association of Canada checked seven major stores in various cities and found outdated canned fish in every one -- one store had cans five years out of date.
Bruce Cran of the Consumers' Association of Canada said grocers have to absorb the cost of pulling old product off the shelves so there is little financial incentive to be more diligent.
"If they are doing a weekly check, then how come some of this stuff is years out of date?" Cran asked.
Martin Bashir resigns from MSNBC over Sarah Palin comments
Florida bear attack: Black bear mauls woman's face