Trying to eat healthily has been made more difficult after the latest discoveries unearthed by food scientists.

The York Nutritional Laboratory in Britain tested 93 common foods and found that eight of the 25 which produce an allergic reaction were pulses, fruit or vegetables. Symptoms such as lethargy, eczema, migraine and depression can be caused by apparently innocent foods like blackcurrants, kidney beans, tomatoes and peas. Even the supermodel's favourite, lettuce, triggers allergies.

Recent research has also found that mayonnaise and salad dressing, both supposed to be bad for your heart because of their fat content, are actually good for you.

Harvard University nutrition expert Dr Frank Hu says that two tablespoons (30ml) of mayonnaise or salad dressing every day reduces the risk of a heart attack. This is because they contain a type of polyunsaturated fat known as ‘a-linoleic acid’ that helps reduce cholesterol.

If you think that the fat-free versions of mayonnaise and salad dressing must be better for you, you are in for a surprise. Their a-linoleic acid has been removed along with the fat. So stick to the full-fat versions says Dr Hu, whose research will no doubt be welcomed by reluctant slimmers all over the world.

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