When it comes to fruit and vegetables, one unwritten rule that's firmly inscribed in our brains is that we have to buy them fresh - that is, unprocessed and freshly picked. However, few of us are aware that the apples or pears we can get at our local supermarket could in fact have been picked as far back as four or five months prior to the moment when we're actually bringing them home. Things are pretty much the same with vegetables and even more complicated when we think of meat, particularly fish. So, given the choice between food preserved by freezing and canned food, which one is the healthiest alternative?

For a long time, frozen food was seen as nutritionally inferior to canned food. However, we have to take into account the fact that freezing techniques have evolved and become extremely efficient in recent years, so that fish, for example, is being caught at sea, cleaned and frozen literally within minutes, which means that when we take it out of the freezer at home and defrost it, it's almost as if we had bought it fresh. The same goes for vegetables. The important thing is to clean and wrap the food properly, so that no ice crystals come into contact with the veggies or the meat and cause freezer burns. However, properly frozen food retains most of its nutrients - such as vitamin C, for example.

Canning on the other hand implies processing the food - heating the can at high temperatures to prevent any bacteria from damaging it - however, this means that the food has been irretrievably altered and some of its most precious nutrients are lost. Some canned foods - vegetables, mostly - are preserved using brine (salt and water) or vinegar, which adds enormous amounts of salt to your diet, having negative effects on blood pressure and not only. As for canned fruit, they are often canned in syrups, which means that they contain a large amount of added sugar. In conclusion, if you have a choice between frozen and canned, it's slightly safer to go with the frozen vegetables or meat. Always read the nutritional values on the packaging and check the salt levels.