Chewing Over Sweetner Claims

By Laura Johannes
Wall Street Journal
February 7, 2006

CAN GUM, CANDY AND MINTS actually be good for your teeth? Producers of products made with a natural sugar substitute called xylitol say the sweetener interferes with cavity-causing bacteria. Dentists say xylitol does have powerful anticavity action, but warn that many products in the U.S. don't contain enough of it to be effective.

Xylitol is a natural substance found in fruits such as raspberries. It has a sweet taste similar to sugar, with about one-third the calories. Approved by the Food and Drug Administration as a food additive, it is harvested from birch wood or other natural sources. It is sold as a powder, or as an ingredient in toothpaste, mouthwashes, gum, candies and mints.

Of course, any sugar-free gum or candy can improve oral hygiene if it helps you avoid sugar. Mutans streptococci, the bacteria that cause cavities, use sugar to make energy in a process that releases lactic acid. Lactic acid, in turn, dissolves the minerals in teeth.

But a growing body of scientific research shows that xylitol not only doesn't feed these bacteria, but that it also actively interferes with their functioning. How this happens isn't fully understood, however studies have shown that in the presence of xylitol, mutans streptococci produce less lactic acid, says Jason Tanzer, a dentist and microbiologist at the University of Connecticut Health Center in Farmington, Conn. Some scientists believe that xylitol also interferes with the ability of the bacteria to stick to your teeth.

Studies of schoolchildren around the world have found that chewing xylitol-sweetened gum was associated with a 30% to 60% reduction in cavities -- and several found it more effective than gums with other sugar substitutes. A National Institutes of Health-funded study in this month's Journal of Dental Research found that chewing gum with 7 to 10 grams a day of xylitol for five weeks reduced cavity-causing bacteria in plaque tenfold. Chewing gum with only 3.44 grams a day of xylitol, or with other low-calorie sweeteners, didn't affect the bacteria.

Some scientists say children can help prevent tooth decay by chewing xylitol gum as soon as their second teeth begin erupting. And, since cavity-causing bacteria can be transmitted by mothers to their infants -- possibly due to the physical closeness -- new mothers can cut tooth decay in their children by chewing xylitol gum while their infants' first teeth are erupting. Adults at risk for tooth decay, for example those taking medications that cause their mouth to be dry or seniors too frail to go to the dentist, can also benefit.

But be careful when choosing xylitol products, says Peter Milgrom, a professor of dentistry at the University of Washington in Seattle and lead author of the NIH-funded study. Many products in the U.S. -- such as Orbit and Trident gums -- use multiple sweeteners and don't have enough xylitol to fight cavities, he says.

Dr. Milgrom, who receives no funding from commercial interests, recommends gum sweetened only with xylitol, such as Epic and Spry; Lotte and Carefree Koolerz also have high xylitol content, he says. To get enough to fight cavities, you'd need to chew at least two or three pieces three times a day, he adds.

Orbit manufacturer Wm. Wrigley Jr. Co. and Cadbury Adams USA, a unit of Trident maker Cadbury Schweppes PLC, declined to say how much xylitol their gums contain. But both say sugar-free gum fights cavities by stimulating production of saliva; saliva reduces acidity in the mouth and contains minerals that help rebuild teeth. Dr. Milgrom says the saliva stimulation may provide a small benefit at most. Cadbury Adams adds that some scientific studies show that only small amounts of xylitol are needed to help fight cavities.

If you try xylitol, don't overdo it. More than 30 to 40 grams a day of xylitol in someone not accustomed to it can cause gas, intestinal cramping and diarrhea, scientists say.