I am 49 and my breath smells metallic. I am very conscious of this, so clean my teeth regularly, use mouthwash and gargle. Can you shed any light on what might be causing this?
Cleaning and mouthwash don't necessarily get rid of gum disease that lies below the gum line around the roots of the teeth. Your first visit should be to a dentist, to find out whether you need an appointment with an oral hygienist to dig out food residues and plaque there. However, there are other possibilities, such as a problem with your nerves of taste and smell. Can you taste food as you used to? The senses of taste and smell are closely interlinked, so if there is a taste disturbance, that needs to be investigated, too. Do other people find your breath offensive, or is it only you? The answer makes a lot of difference. Breath smells can come from the lungs and stomach, as well as from the mouth, nose and throat, so a doctor's visit may also be in order. However, if you are otherwise well and healthy, deep gum disease remains the most obvious cause. There are prescription drugs that can cause metallic tastes: are you on regular medication? If so, discuss that with your GP.

I'm a breastfeeding mother and, since starting to feed my son six months ago, I have experienced cravings for chocolate, cake and all things sweet and sugary – which is quite unlike me. All the other breastfeeding women I know have had a similar experience. Is there any physiological reason?
Yes, and it's a fairly simple one. You are passing over to your baby a lot of extra carbohydrate in your milk, and your body needs to replace it both to provide you with energy and so you can produce more milk. We tend to underestimate the amount breastfeeding mothers really need. So when you crave these sweet foods, this is a sign that you need the extra – that's all. You can replace your breast milk sugars faster and easier by eating sugary foods than you can by consuming extra starches, proteins or fats. Your body knows what it needs and makes you crave it.

• Do you have a question for Dr Smith? Email doctordoctor@theguardian.com