Bad breath is one of those subjects that we tend to avoid discussing. According to the British Dental Foundation, whether your friends are honest enough to tell you that you have it depends to some extent on where you live. While 72 per cent of those surveyed in Southampton and Edinburgh would tell you, only 56 per cent in Cardiff would do so and half of all Londoners questioned admitted that they would keep shtoom.

While the British Medical Journal says that estimates of halitosis prevalence are unreliable, several studies report that about half of the population is affected. Bad breath can be caused by a pungent meal or bad nutrition, or it may be a symptom of underlying medical problems such as strictures in the oesophagus, sepsis in the lungs, undiagnosed diabetes, chronic sinusitis, tonsillitis or even liver failure.

Whether someone has said that you suffer from it or you just have a sneaking suspicion, it can be medically diagnosed through the “organoleptic test scores” process, which involves one or more examiners sniffing your exhaled breath on two or three days under controlled conditions. Much simpler is to lick the inside of your wrist, wait for ten seconds and have a sniff. If the odour is unpleasant, your breath may be as well.

If so, the first port of call is your dentist, who will refer you to your GP if he or she feels that any of the medical problems above may apply. Often, though, persistent bad breath is a sign of gum disease caused by plaque, the sticky, colourless film of bacteria that forms constantly on our teeth.

As the American Dental Association explains, these bacteria create toxins that irritate the gums. Good dental hygiene, including brushing twice a day as well as flossing, is crucial to resolving this problem.

Chewing sugar-free gum sweetened with xylitol is also worthwhile. Xylitol is a natural sweetener found in fruit such as cherries and in the wood of the birch tree, from which it is extracted for commercial use. Studies in Scandinavia have suggested that it helps to buffer acidity and reduce the build-up of plaque-causing bacteria in the mouth.

Xylitol, which is also used in some sugar-free sweets, has been shown to increase saliva flow, which in itself is an important step in tackling bad breath. The drier your mouth, the more bacteria thrive there. Saliva flow is reduced if you breathe through your mouth and if you skip meals – because the less you chew, the less saliva you produce. So breathing through your nose and eating regularly are sensible steps to take.

Drinking regularly also helps to prevent the mouth from drying out – and green tea, according to Japanese scientists, is a good choice. It is packed with antioxidant polyphenols and they claim that it promotes healing of damaged gums. In extreme cases it is possible to be prescribed artificial saliva to help to reduce dryness in the mouth.

When it comes to common-sense self-help cures, it is worth pointing out that none is backed with clinical evidence of efficacy – but then, there is precious little evidence to support the halitosis-fighting claims made on behalf of most mouthwashes, either – which means that it’s well worth taking a look at the kind of remedies that medical herbalists and “old wives” recommend.

Chewing fresh parsley is at the top of the list. Parsley is rich in the green pigment chlorophyll, which has long been recognised as a powerful breath freshener. Chlorophyll is also available in “green” drinks such as wheat-grass, and in spirulina tablets, which must be chewed thoroughly to unleash their breath-sweetening potential.

Putting a couple of drops of peppermint oil on your tongue a few times a day is said to help because, as well as having a nice aroma, it is believed to be effective in killing bacteria. Chewing fennel or anise seeds – or, if you can cope, a few fresh cloves – may also have a freshening effect.

Perhaps the most obvious advice is to try to avoid foods such as garlic and onions. Sadly, however good these may be for our hearts, once absorbed into the bloodstream their pungent odours are transferred to our lungs, from which they are expelled in our breath.

Avoiding sugary foods between meals is also important to minimise plaque build-up.

On the other hand, some foods are worth trying, especially berries, which are rich in the vitamin C needed for strong gums. The supplement Coenzyme Q10 may also be worth a go. It is found in all living cells, but supplementing with 50mg twice a day may help to heal damaged gums.

Some complementary practitioners also recommend probiotics and lots of fibre-rich foods to improve the function of the large intestine, which they say can affect our breath. Both of these are good for general health and unlikely to do any harm.

Finally, however hard you try to mask it, if you smoke your breath will always smell like an ashtray.

www.amandaursell.com

For sweeter breath

Yes: chewing gum with xylitol; green tea; parsley; spirulina tablets; peppermint oil; fennel, anise seeds or cloves; berries; Coenzyme Q10.

No: Garlic; onions; sugary foods between meals.

Do you have a nutritional topic that you would like Amanda to cover?

E-mail amanda.ursell@thetimes.co.uk

Write to: times2, 1 Pennington Street, London E98 1TT.

Amanda cannot enter into personal correspondence.

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