Nutritionists often suggest keeping a food diary to track your meals, avoid mindless overeating and keep tabs on nutrients like salt, fat and vitamins. But writing down everything you eat is tedious, and many people find themselves abandoning their efforts after a few days or weeks.
In the future, you may be able to track your food intake with a sticker—mounted on your tooth. Researchers at Tufts University have developed a tooth sensor that can track glucose, salt and alcohol, and wirelessly transmit the information to a device.
The two-millimeter-by-two-millimeter flexible sensor can bond to a tooth’s minutely bumpy surface. The sensor has three layers: two outer gold rings, and an inner layer of a bioresponsive material that’s sensitive to glucose, salt and alcohol. These substances shift that material's electrical properties and cause it to transmit a different spectrum of radiofrequency waves. Together, the three layers act as an antennae, broadcasting the information to mobile devices, like phones or tablets.
While the material in the prototype is only sensitive to glucose, salt and alcohol, the researchers hope to develop it to detect a far wider range of chemicals and nutrients.
“If you can evolve the sensor and engineer it to have a database of food consumption, then you could think about nutrition management,” says Fiorenzo Omenetto, a professor of engineering who led the research. “That could be reminding us that we’re indulging too much in sugar or something like that.”
Scientists have developed wearables for monitoring food intake before. Most of these have been in the form of mouth guards. Japanese researchers designed a device to monitor uric acid and American and Brazilian scientists created another to monitor glucose; both contained biosensors and wireless communications modules. But these require, well, wearing a mouth guard, which as any tooth-grinder knows, can be uncomfortable.
Diabetics could theoretically use the new tooth-mounted sensor to monitor their sugar intake and broadcast the information to their doctors. It could be helpful for people with other medical conditions that require them to monitor their eating, for example, patients with high blood pressure who need to limit their salt, or people with celiac disease who need to completely avoid gluten.
The device could also potentially detect physiological states, like changes in saliva that signal developing gum disease. Or perhaps it could detect chemical markers of fatigue, warning you you’re too tired to drive.
"This study is an interesting proof-of-concept demonstration that small, wireless biosensors can detect changes in saliva due to the presence of compounds such as salt, sugar and alcohol," says Ben Almquist, a professor of bioengineering at Imperial College London.
But, Almquist says, there will be "significant hurdles" before the technology is ready for daily use as a food diary substitute.
"For instance, for continuous monitoring of food intake, the sensors will need to be robust enough to withstand abrasion during chewing. In addition, foods are complex mixtures of compounds including salts, sugars and proteins, and the relative amounts of each that enter into saliva will depend on factors such as the nature of the food (e.g. cooked versus fresh), the amount of chewing, and the time in the mouth before swallowing."
But other, less complex uses may be closer at hand, Almquist says. Detecting compounds in saliva like lactate, which is important in monitoring critical care patients, as well as athletes during training, could be simpler to achieve.
Then, there's the critical question of aesthetics: how many people want what basically looks like a computer chip on a tooth?
“It’s a bit of a leap of faith – some people may find it horrible,” jokes Omenetto. “You could make [devices] that are shaped like a flower or something.”
In truth, the sensor could simply be mounted on a back tooth where it’s not visible. The front tooth was used in Tufts’ press materials simply to show off the technology. The tooth in question belongs to Logan Garbarini, an engineering undergraduate who worked on the research and is a co-author on the paper.
“He’s one of the most talented undergraduates I’ve had in some time,” Omenetto says. "And his incisors have become very famous."