Q. I frequently have bad breath. Are there any foods that can help?

A. Millions of bacteria live in the mouth, particularly at the back of the tongue. Bad breath results from decayed food particles and sulfur compounds released by these bacteria. The bacteria in our digestive tract can also affect our breath.

In addition to brushing your teeth after meals, brush the back of your tongue and floss daily. These steps remove food particles before they decay. Don't forget about your molars — food and bacteria love to hide there.

Keep your mouth moist by drinking lots of water. When your mouth is dry, dead cells adhere to the tongue and inside of the cheeks. Bacteria use these cells for food and expel foul smelling substances.

Chewing sugarless gums that contain an ingredient called xylitol stimulates saliva flow and flushes away food particles and dead cells.

Certain herbs have a cleansing effect on the breath. These include: anise, cardamom, cloves, coriander, eucalyptus, parsley, rosemary, spearmint and tarragon. You can chew on fresh herbs or steep them in hot water. These herbs can also aid digestion when eaten at the end of a meal.

Yogurt can reduce the level of odor-causing hydrogen sulfide in the mouth. It also helps prevent tooth plaque and gum disease. Be sure the yogurt contains active cultures and is sugar-free.

Plaque buildup inside the mouth can cause unpleasant odors. Apples, carrots, or celery can decrease plaque buildup and increase saliva production. These foods keep the mouth moist and rinsed out.

Citrus fruits, melons and foods rich in vitamin C create a hostile environment for bacteria. These foods can also prevent gum disease and gingivitis, both causes of bad breath.

Vitamin D in yogurt, cheese and milk also creates an inhospitable environment for bacterial growth.

Mints and mouthwashes can mask bad breath, but only temporarily. In fact, most mouthwashes contain alcohol, which dries out the mouth and decreases saliva flow.

Be careful of garlic and onions. They contain chemicals that linger in the mouth, then are absorbed into your bloodstream and expelled through your lungs. These odors disappear over time, once the offending substance is cleared out of the body.

If, despite your best efforts, your breath is still unpleasant, see your doctor or dentist to rule out physical disorders such as gum disease, sinus infection, diabetes, liver or kidney disease.

Amy Tousman is a registered dietitian with the Health Education Center of Straub Clinic and Hospital. Hawai'i experts in traditional medicine, naturopathic medicine and diet take turns writing the Prescriptions column. Send your questions to: Prescriptions, Island Life, The Advertiser, P.O. Box 3110, Honolulu, HI 96802; fax 535-8170; e-mail islandlife@honoluluadvertiser.com. This column is not intended to provide medical advice.