The chopstick device has a copper electrode on the hand side and a titanium electrode on the mouth side, and each electrode is connected to a current output device independently. Credit: Kirin Holdings Co., Ltd.
If the popularity of fad diets is any indication, people will do most anything to either eat healthier or lose weight. In a new study, Japanese researchers have devised a “shocking” technique that can help people consume less salt in their daily diet.
An estimated 2.5 million global deaths per year could be prevented if individuals cut back their salt consumption to the recommended daily intake of less than five grams, according to the World Health Organization (WHO).
Yoshinobu Kaji and colleagues at Meiji University developed a chopstick-like device that uses a weak electrical charge to stimulate how the tongue experiences saltiness.
“Many people consume around twice the salt intake standard recommended by the WHO,” said Kaji, lead author of the study, published in Frontiers in Virtual Reality. “This standard cannot be met with a little effort in salt reduction, and a drastic solution is essential.”
The chopstick device has a copper electrode on the hand side and a titanium electrode on the mouth side, and each electrode is connected to a current output device independently. When food is ingested, a circuit is formed in the human body, and electrical stimulation can be applied to the tongue.
Kaji and his team gently zapped their own taste buds before testing the effects of the electrified chopsticks in two separate experiments involving 36 people previously or currently on a low-sodium diet.
The participants experienced the electrical stimulation waveform at 0.5 mA before performing the task. If they did not experience any severe discomfort, the experiment continued. However, if the electrical stimulation caused severe discomfort, the experiment was conducted using the waveform at 0.3 mA.
The first experiment investigated the saltiness enhancement effect of electric taste using saltwater gel samples with the same saltiness as low-sodium and ordinary foods. The participants ingested a .80% saltwater gel sample with no stimulation, a .56% saltwater gel sample with no stimulation and a .56% saltwater gel sample with electrical stimulation.
The study results showed electric stimulation enhanced the saltiness of the low-sodium sample, making it comparable with the control sample—even though it was 40% saltier.
The second experiment was designed to evaluate the saltiness enhancement effect and the change in flavor that may occur with electric taste sensation when eating or drinking low-sodium food. The participants were asked to dip the tip of the chopstick device into a cup of low-sodium miso soup and sip it—both with and without electrical stimulation.
A similar “saltiness enhancement” result seen with the saltwater gel samples was also recorded for the miso soup samples. Additionally, many participants commented on the soup had a better mouthfeel and taste.
“The results indicate that electrical stimulation may have affected the umami taste as well, and that saltiness may have been enhanced, resulting in a better taste balance,” the researchers explain in the study. Umami is a fifth sensory taste often described as savoriness.
However, there were negative comments regarding taste that included bitterness, minerality and irritation. The scientists think these reactions are caused by the high intensity of electrical stimulation.
Importantly, in both experiments, more than 80% of the participants said they could tolerate the electric stimulation on a daily basis. But, approximately 10–20% of participants reported experiencing discomfort that was “unbearable in daily life,” suggesting significant individual differences in how people experience electrical stimulation.
The researchers say future research will need to search for “stimulation waveforms, design devices and calibrate currents for each individual to suppress discomfort while maintaining the taste-enhancing effect of the electric taste.”
While Kaji’s long-term goal is to develop a commercially available chopstick-shaped device for daily use by those following a low-sodium diet or trying to reduce their salt intake, the Meiji University team is investigating other uses for their innovation— such as stimulating taste as part of a virtual reality experience
“In the future, for example, it may be possible to virtually reproduce the taste of food and drink, or to realize taste expressions that are difficult to achieve with conventional eating experiences,” concluded Kaji.