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Health Check: is fresh food always the best choice?

When it comes to food, we’re told to eat what’s in season, buy locally and avoid “food miles” – for good reason. But not everyone has access to grower’s markets, or the time and resources to source and…

Buying fresh and cooking from scratch is a struggle for some. Shutterstock/sunlover

When it comes to food, we’re told to eat what’s in season, buy locally and avoid “food miles” – for good reason.

But not everyone has access to grower’s markets, or the time and resources to source and prepare ingredients from multiple locations. Even buying fresh and cooking from scratch is a struggle for some.

Foods that have been preserved by freezing, canning or drying are certainly not in vogue but this doesn’t mean they’re nutritionally inferior. Preserved foods are often a nutritious, cheap and convenient alternative to fresh produce.


Frozen vegetables are harvested ripe, at their prime, when they have optimal nutrient content. They’re then snap frozen, often on the site of production, locking in most of the nutrients.

While there may be minor losses of water soluble vitamins such as vitamin C due to the initial blanching, most of the vitamin and mineral content remains intact.

The texture of frozen vegetables does change due to the formation of ice crystals that break down some of the plant cell walls, making them less crispy. But this doesn’t significantly damage the fibre content.

Freezing berries helps make the most use of a fragile and seasonal crop. Olivier Deveault/ Flickr

In comparison, fresh fruit and vegetables are often harvested before they’re ripe, placed in cold storage or transported long distances and spend time in storage at markets and supermarkets. This process leads to continued losses of the less stable vitamins.

Studies comparing the nutrient content of frozen and fresh vegetables have often found the frozen varieties to be nutritionally superior, because loss of the water soluble vitamins is slowed considerably by freezing. Fat soluble vitamins and minerals are heat stable, so they’re less likely to be affected.

We know less about the effect of preserving on the phytonutrients in food. These compounds – such as anthocyanins in frozen berries – are not essential for the human body but seem to have health benefits.

Berries are extremely seasonal because they deteriorate quickly, meaning they are often unavailable or expensive. As a result, large proportions of berry harvests are frozen to allow maximum use of the crop and maximum availability. So far, studies have shown freezing berries results in only a small loss of anthocyanin.


Canning can lock in the nutrients of fruits and vegetables, making them edible for months or even years.

But when fruits and vegetables are heated during the canning process, the water soluble nutrients – vitamin C and Bs – decline considerably.

The heat-stable vitamins E and A are much less affected, as are carotenoids and minerals.

Once canned, the food and nutrient content is stable. Flickr/USDAgov, CC BY

Perhaps surprisingly, canned tomatoes may be nutritionally superior to fresh varieties because of the increased presence of lycopene, a phytonutrient that may decrease the risk of cancer.

Lycopene is tightly bound to the fibre structures in tomatoes; the process of canning helps break down the fibre structures, releasing the lycopene and making it more easily absorbed by the body.

When it comes to canned fruit and vegetables, be wary of salt and sugar content. Buy canned fruit packed in natural juice rather than syrup and choose no added salt canned vegetables.


Dried fruit is a convenient way to add variety and improve nutrition. It’s compact, easily stored and transported, high in carbohydrates and fibre, and makes a great snack on the run.

Dried fruit is high in energy (kilojoules), as the drying process concentrates the sugars. But it also has higher concentrations of more stable nutrients such as calcium and iron, as well as phytonutrients.

The fruit drying process concentrates the sugars and some key nutrients. Pavels Rumme/Shutterstock

One study showed greater amounts of phenolic compounds – which may have antioxidant effects and protect against heart disease and cancer – in dried compared with fresh figs.

Be aware that some dried fruit can contain sulphur dioxide, a pre-treating agent that maintains the original colour of the fruit, which causes sensitivity in some people, particularly asthmatics. If you’d rather avoid sulphur dioxide, buy the brownish rather than the orange dried apricots.

The verdict

Fresh can be best when the food is in season, inexpensive and and at its peak for flavour, texture and nutrient content. But if foods are out of season, likely to have been stored for an extended time and are expensive, frozen, canned and dried fruit and vegetables are a good alternative to boost variety and nutrition.

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8 Comments sorted by

  1. David Briggs

    logged in via Facebook

    Thank you for this article. I do dispute however that food miles is a good metric for guiding food consumption. Food miles is often invoked to indicate the environmental cost of food production, most notably the transportation task to deliver food to your doorstep. But food miles is not a reliable guide to the energy embodied in food production, and has no link to environmental harm ( or environmental stewardship). As you demonstrate, food miles I'd not a reliable guide to nutritional value either.
    In the end it appears that food miles has been used as a trade promote Australian food over imported food. But we need to be careful about making this argument. Our farmers rely on exporting to other nations. It would be a shame to see our farmers harmed by policies that have spurious foundations

  2. Jane Middlemist


    As with other issues, one of the main keys to a healthy diet is knowledge - knowing what to look for when shopping for food. Articles like this one are a valuable aid in making that knowledge accessible to everyone.

  3. Michael Santhanam-Martin

    PhD Candidate in the Rural Innovation Research Group, Melbourne School of Land and Environment at University of Melbourne

    This is a very useful contribution to the "food futures" discussion. Thanks! At the other end of the supply chain, having stable markets for less perishable goods (and multiple market channels in general) is a big plus for farmers. Finding ways to conserve excess food an harvest time, for later consumption, is of course an age-old practice. How to fermented and pickled products compare nutritionally?

  4. Arnaud Deladeriere

    Postdoctoral fellow at University of Cambridge

    Great article, and very much towards the habits people should follow. However, even if you eat canned, dried or frozen food, you can always check where it comes from and therefore still eat local and reduce food miles.

  5. Evelyn Haskins


    But IS food that has been harvested when unripe, stored over extended periods and/or artifically ripened FRESH! ?

    Aren't you here confusing, here, fresh with raw?

    What is the comparble loss of nutrients (or improvements) of raw food cooked at home/restautrant just before eating, and raw food cooked in a factory and canned/frozen?