We've heard a lot recently about eating the wrong foods and cancer. Bacon, red meat, processed foods, salt, refined sugars, alcohol, smoking - even vitamin supplements - have all been blamed for causing cancer. Is there a league table of how much of each gives what risk?

Good question. Smoking is by far the worst of these habits - 20 a day raise your risk of lung cancer by between 20 and 40 times. For women it's nearer 40 than 20. As for all the others, the risk is relative to the amounts you eat and how genetically susceptible you are to cancer. If I had to give a league table, I'd put smoking first, alcohol a reasonably close second, obesity a fairly far-off third and the others (processed and red meats, salt and dietary supplements) quite a long way behind, but still something to think about. If you want to lower your risks further, then daily physical exercise, plenty of fruit and vegetables, and keeping a normal body shape will help. But nothing's certain.

I'm 24. In the past few months my lower jaw seems to have grown, so that my face has changed. Would it be wasting my GP's time to see her? I feel healthy, and have no other symptoms.

You must see her. Any facial changes after you have stopped growing can be a sign of general health problems or a particular problem in the bones of your face. Lower jaw overgrowth can be a sign of excessive pituitary gland activity, and that may have to be ruled out. Show your doctor a photograph of yourself before the change, so a good comparison can be made.