Their findings suggest a new inroad for the food industry into the growing functional food fad as well as a challenge to the dominant probiotic dairy products market in Europe, currently worth around €1 billion.
"Our study shows that chewing gum can be a functional food, having a significant impact on oral hygiene over the short term, if it contains antimicrobial agents such as cinnamic aldehyde or other natural active compounds," said Christine Wu, professor of periodontics at the University of Chicago and lead author of the study.
Presenting her findings at a recent conference Wu said that because gum contains cinnamic aldehyde, a plant essential oil used for flavouring, the result was not surprising.
Research already carried out on natural antibacterial agents from plant sources that suppress oral pathogens had found they inhibited the growth of bacteria responsible for cavities and periodontal infections.
"In laboratory tests, some of these oils also prevented the growth of three species of oral bacteria associated with bad breath and the production of volatile compounds that cause the unpleasant smell," added Wu.
In the small clinical trial, a link up between Wrigley and Wu, 15 subjects chewed one of three gums for 20 minutes: Big Red, the same gum with natural flavours but no cinnamic aldehyde, or a gum base with neither flavours or oil.
Twenty minutes after the subjects stopped chewing the gum, their saliva was tested and compared with samples collected before chewing began. Microbiological analysis showed that Big Red reduced the concentration of anaerobic bacteria in the saliva by more than 50 per cent.
"It was particularly effective against anaerobic bacteria residing at the back of the tongue, reducing the population by 43 per cent," said the researcher. These bacteria produce volatile sulfur compounds through the putrefaction of proteins and are considered the major contributors to halitosis, or bad breath.
The gum that contained natural flavours but no cinnamic aldehyde also reduced the number of bacteria by about 40 per cent.
"The result was puzzling at first, but after compiling our data, we were informed that the natural flavours included a small amount of a plant extract," said Wu. "We had already shown in previous lab studies that this extract suppresses the growth of oral pathogens," she added.
The gum base without flavours or cinnamic aldehyde produced no significant reduction in oral bacteria.
"The product doesn't just mask foul mouth odour; it eliminates the bacteria that cause it, at least temporarily," concluded Wu.
Sugar-free gum has been enjoying strong growth in Europe. In Spain alone a recent survey by market analysts AC Nielsen revealed that in 2001 sales of chewing gum rose by 10 per cent year-on-year to €121.9 million in 2001, compared to sales of sugar confectionery that increased by 6.3 per cent year-on-year. But there are signs that gum could soon be moving in the functional food direction.
In February this year Danish chewing gum maker Gumlink claimed to have formulated the world's first gum enriched with vitamins. The patent-pending product has two layers - chewing gum combined with a non-chewing gum layer that allows it to add ingredients that cannot support traditional gum manufacture processes. The compressed gum is made at low pressure and low temperatures, presenting possibilities of new combinations.