Food myths debunked

Q: Is it true that canned foods have no nutrients?
Canned foods are a very useful standby in the store cupboard as they last a long time. Some canned foods are much lower in nutrients than fresh or frozen because the heat process of canning reduces them a lot.

In particular, vitamin C is damaged (though useful amounts are still provided by canned red fruit and baby sweetcorn) and some oily fish such as tuna is 'de-fatted' during canning and so does not contain valuable omega-3 fatty acids in very high amounts compared to fresh.

However, useful canned foods include beans which are still rich in fibre and minerals, canned tomatoes which are high in lycopene (see answer above), canned salmon and sardines which are very good sources of calcium. It is best to choose canned foods that are low in salt and sugar.

Q: How long can you keep leftovers in the fridge?
Firstly, it is important to keep your fridge at the right setting recommended by the manufacturer. Refrigeration doesn't stop bacteria multiplying but slows them down a lot. Cool cooked food and then put in the fridge very soon after cooking as this reduces the chance of bacteria multiplying.

Divide large amounts of leftovers into smaller containers to chill thoroughly and quickly in the fridge. Use leftovers within 2-3 days of initial cooking or freeze before then. When heating leftovers make sure they are cooked through thoroughly and are piping hot. Always keep raw food away from cooked food to avoid cross contamination with bacteria.

Q: How safe is it to eat raw meat, like carpaccio, steak tartar, or raw fish, like sushi?
Raw meat is a source of bacteria such as salmonella, listeria and E.coli as well as parasites. Ideally, these foods should be cooked but given that they are often eaten as part of more adventurous diets it then becomes essential to be sure that the ingredients are very fresh.

If buying raw meat or fish to prepare yourself, make sure that you have ice packs available for transportation and that the ingredients are used immediately. Raw meat or fish is not recommended at all for pregnant women, children, the elderly or those with compromised immune health.

Q: The best way to cut down on salt is to get rid of the salt shaker, right?
The salt you add at the table or to your cooking will, at most, contribute 20 per cent of your daily salt intake. By far the larger proportion, 80 per cent, comes from packaged and process foods. Obviously, salty foods are crisps, salted nuts and other snacks. Convenience foods such as hamburgers, pizzas, smoked and cured foods such as bacon, and sausages are very high in salt.

But many people do not realise that everyday staples such as breakfast cereals, cheese and bread are major contributors. The best way to cut back on salt is to cook fresh options instead of pre-packaged. For instance, use dried pasta instead of canned or frozen peas instead of canned, limit takeaways and to not use salt in cooking (for instance, it is pointless adding salt to boiling water for rice or pasta).

Q: I've heard trans fats are bad for you but how do I know how to cut them out of my diet?
Trans-fats are unhealthy fats linked to heart disease and some cancers. They do occur naturally in the diet, but in very low amounts. The problem is that food manufacturing has introduced hydrogenated fats - which are artificially hardened vegetable oils - to prolong the shelf life of processed and packaged foods and because it is a cheap ingredient and these contribute high amounts of trans-fats.

Some countries have taken the step of banning high levels of trans-fats or insisting on labelling, but this has not yet happened in the UK. Takeaway foods are often very high in trans-fats. The best way to reduce your intake is to cook more food from fresh, avoid deep-fried takeaways, avoid margarines that use hydrogenated oils, and limit crispy foods such as biscuits and crisps that rely on hydrogenated fats.

Q: Is or isn't organic food more nutritious than non-organic?
This debate has been simmering for a while and is still not conclusive, though it looks like the nutrient levels of organic food is coming up trumps. Certainly, as farming has become more intensive over the years the level of nutrients in foods now compared to 50 years ago appear to have fallen (though this could be linked to different testing methods).

Nevertheless, recent studies have shown that certain nutrients, such as omega-3 fatty acids are higher in organic milk, and organic vegetables have higher levels of vitamin C and some other antioxidant nutrients called polyphenols.

Q: My life is really busy so I find it hard to get five portions of fruit and veg a day, so is it okay if I just munch through five apples?
The reason that five portions of fruit and vegetables are recommended is that this minimum level is linked to a reduction in risk of a number of diseases including digestive diseases, heart disease and cancer. It is thought that this is linked to vitamin, mineral, antioxidant and fibre intake.

However, the recommendation is to eat five different types of fruit and veg daily, and this is because they all offer different levels of these nutrients. If you are eating on the run, easy ways to achieve this is to keep a handy supply of easy-to-eat fruit (such as apples, bananas, grapes) available, to also include easy vegetables (such as scrubbed carrots or cherry tomatoes) or snack on dried fruit (such as apricots or prunes).

When you do eventually sit down for a meal, start with a vegetable soup, include some salad or cooked veg, enjoy bean or lentil dishes or dips like hummus, and have a fruit-based dessert.