When it comes to vegetables, which is the best food choice: frozen, canned or fresh? Nutritionally-speaking, there is no better choice than fresh. However, the longer these vegetables stay on the farm stand or your grocer's shelves, the more they lose their nutritional value.
A study last year by the University of California Davis found that green peas lost over 50% of its vitamin C within 24 to 48 hours after picking.
So unless you're getting the freshest of peas, frozen peas would be a healthier choice. The freezing process right after harvesting locks in the nutrients until they're defrosted. Canned vegetables, on the other hand, lose much of their value when they are subjected to the intense heat caused by the canning process.
But when it comes to the various vegetable production and distribution systems, and their impact on the environment, the calculation gets a bit trickier. Fresh, locally-grown vegetables are a good choice for the reduction of carbon imprint. But keeping them cool at home requires refrigeration, which requires not only electricity, but also hydrofluorocarbon, the main ingredient in fridge coolant, which has a global-warming potential 3,200 times that of carbon dioxide.
Then there's the consideration of food distribution: Eating food that's out of season in your area means buying produce that has likely been flown thousands of miles to get to your dinner table.
According to Lucy Siegle, in her article "Is It Better to Buy Canned or Frozen Food?" that was published by the Guardian, the "core use" of freezing "should be to freeze local or homegrown surpluses to tide you through the winter."
She also argues the benefits of canned vegetables, noting that "tins of food will sit there happily until the apocalypse arrives." In addition to requiring zero energy to store and lasting for years, cans also benefit from an established recycling industry that puts back about 25 percent of recycled material into new products.
"In either case," Ms Siegle concludes, "I'd rather have canned or frozen than the 'chilled' goods that increasingly stock our fridges, which are chilled throughout the supply chain and sold in open chiller cabinets competing to stay cool in heated shops. These are the products that should be given the cold shoulder."
GET INFORMED
- Read "Is It Better to Buy Canned or Frozen Food?" (The Guardian, September 14, 2008)
- Download a PDF of "Nutritional comparison of fresh, frozen and canned fruits and vegetables, Part 1, Vitamins C and B and phenolic compounds" (University of California Davis, 2007)
- Download a vegetable season guide (Center for Urban Education About Sustainable Agriculture)
- Download the "Pocket Eco-Friendly Fish Selector" (Environmental Defense Fund)
