People are often surprised when Renata Herrera Rojas, a fifth-year university student flatting in Dunedin, says she eats just as well as she did at her home – even though she uses some canned food.
But many students struggle: a 2024 University of Auckland survey found 45 percent of 347 students, especially those living away from home, faced food hardship. And the Otago University Student Association has seen rising food bank demand over the past few years.
“There’s this massive culture around that; ‘this is just what’s going to happen. This is what’s normal, that you’re going to be eating bad food for this number of years, and that’s totally fine’, and like a kind of complacency around it,” says Herrera Rojas, who has created the Beginner’s Guide to Nourishment.
Dunedin law and global studies student Renata Herrera Rojas has written a manual to make cheap and healthy student eating easy.
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Canned foods are a staple among students, Herrera Rojas says. They also offer convenience – for example, removing prep work on corn or legumes.
Nutritionist Julie North says they offer affordable access to produce that might otherwise be too costly or out of season — a better option than skipping those foods entirely. (Early University of Auckland survey findings also show students aren’t eating enough fruit and vegetables.)
Food banks in New Zealand often rely on canned food because they’re a long shelf-life product that don’t need as much capacity and resources as fresh food. (file image)
RNZ / Niva Chittock
But aren’t canned foods ‘processed’?
Canned food is “heat treated to produce a commercially sterile shelf-stable product with an air-tight (vacuum) seal,” according to Food Standards Australia New Zealand (FSANZ).
While this is a form of processing, it’s not all bad, North says. Heat treatment kills organisms that cause spoilage or illness.
Processing has long been used to improve food safety, North explains. Other examples include adding folic acid to non-organic wheat flour used in bread-making to reduce neural tube defects.
How do canned foods compare to fresh?
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Heat treatment can reduce some nutrients, especially water‑soluble vitamins like C and B, North says.
“It’s not a hugely significant downgrade, but you would find, compared to eating, say, a fresh peach, there may be less vitamin C in a canned peach.”
But heating can also increase the availability of some nutrients, such as lycopene in tomatoes, she says.
“So there’s pros and cons there around the dietary bioavailability, and it’s not as straightforward as all heating is negative. It can depend on what it is that we’re looking for in the product.”
What about the sugar and salt content?
North recommends checking the ingredients list: fewer ingredients and fewer additives generally mean a more wholesome product. (Salt, water, and simple preservatives like citric acid are common in brines.)
“[Lentils and legumes] are really easy to give a quick rinse under the tap and wash that brine off. That’s also what you would do if you were doing home brining.”
Ali Hill, from University of Otago’s human nutrition department, says syrup sugar content may be trickier to figure out from the nutritional panel because this also includes the fruit’s natural sugars.
For sodium, she suggests comparing the “per 100g” values between products.
“You can also look for “low salt” or “low sodium” on the label, but bear in mind that not all canned foods low in salt will say so on the can.”
Herrera Rojas buys tuna “with spring water and as little stuff as possible” and drains it, rinsing canned beans as well.
“A lot of the time with the other kind of canned foods that I see students consume, like those nacho beans that come with sauces, they’ll come with so much added salt and sugar and other ingredients in there that aren’t really necessary.
“You can buy yourself a range of spices that are going to last you for ages, and you can use them in all of your meals.”
Are there any concerns about the cans?
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Spanish researchers have raised concerns about chemicals migrating from can linings, in particular canned tuna with tomato, marinade, or high fat. They advise against reusing can liquids.
“In most cases, the amounts detected were within the limits established by the European Commission. However, it is important to consider possible exposure through various routes and cumulative exposure over a lifetime,” the researchers wrote in a piece for The Conversation last year.
They also warn against heating food directly in the can, because this might speed up chemical leaching.
FSANZ advises avoiding cans that are swelling, leaking, rusted, scratched, dented, or damaged.
Can I eat it every day?
North says daily consumption isn’t a big problem as long as people eat a variety of foods.
Lab tests by Australian scientists on canned tuna in 2015 suggest – depending on your body weight and the exact brand you buy – you would have to eat anywhere between 25 and 35 small tins (95g each) of tuna a week before you hit maximum mercury limits.
But FSANZ notes unborn babies, infants, and young children are especially vulnerable to excessive mercury intake.
How long can you keep canned food?
Once opened, FSANZ recommends transferring contents to a clean plastic or glass container, covering it, and refrigerating. It shouldn’t be stored longer than the fresh version of the food. (file image)
Unsplash / Roberta Sant
Shelf life depends on storage conditions and the type of food, FSANZ says. As a general rule, unopened cans should be kept in a cool, dry place. Foods with a shelf life over two years don’t require a date and remain safe as long as the can is intact.
They also recommend wiping the top before opening and using a clean can opener – washing it after every use.
How do you store opened canned food?
FSANZ recommends transferring contents to a clean plastic or glass container, covering it, and refrigerating. It shouldn’t be stored longer than the fresh version of the food.
Alternatively, Herrera Rojas suggests using the whole can for meal prep and freezing portions for later.
– Published by EveningReport.nz and AsiaPacificReport.nz, see: MIL OSI in partnership with Radio New Zealand