The development of a new way to measure umami taste sensitivity has revealed a link between the loss of taste sensation and overall poor health in the elderly, say researchers writing in the journal Flavour.
According to the study, led by Noriaki Shoji at the Tohoku University Graduate School of Dentistry, Japan, our overall health as we age may be impacted by our ability to trigger umami taste receptors – which are present in oral tissues and the gut.
“Our newly developed umami taste sensitivity test revealed the loss of only the umami taste sensation with preservation of the other four basic taste sensations (sweet, salty, sour, and bitter) in some elderly patients,” explained the Japanese team. “All such patients complained of appetite and weight loss, resulting in poor overall health.”
As a result, the team suggested that maintenance of umami taste functions could contribute “not only to the preservation of good oral health but also to the general overall health in elderly people.”
The team noted that currently, tests on taste sensitivity and function only assess four of the five basic tastes; sweet, salty, sour, and bitter.
They suggests that because the taste quality of umami, which is recognized as a fifth taste category, is not clinically assessed at present, information about umami taste disorders has yet to be accumulated.
However a newly developed umami taste sensitivity test has suggested some people may suffer from the specific loss of the umami taste sensation, with preservation of the other four taste sensations in some elderly patients.
“T1R receptors, which mediate umami taste, are expressed on cells of both the duodenum and tongue, suggesting that the umami taste sensation functions in nutrient sensation and digestion in the gut,” the researchers said. “This evidence indicates that the ability to detect umami flavours is very important for maintaining a healthy daily life.”
The Japanese team also reported that previous research has linked impaired salivary flow to declines in taste sensitivity – noting that umami taste stimulation increases the salivary flow rate because of the gustatory–salivary reflex.
Shoji and colleagues used Japanese Kobucha (a tea made of powdered tangle seaweed) to stimulate umami taste and promote reflexive salivation in a group of 44 people who had been shown to have reduced umami taste sensitivity according to the new test.
“All patients with an umami-specific taste disorder were >65 years of age, and all complained of appetite and weight loss with resultant poor overall health. Interestingly, the chief complaints of most of these patients were that food was not palatable and that they did not eat normally because of appetite loss,” said the team.
After drinking the Kobucha tea, the team reported that the participants saw improvements in salivation, taste function, appetite, weight, and overall health.
“After improvement of the patients’ umami taste sensitivity, the patients also experienced remarkable improvements in their appetite and weight because food regained its palatability,” wrote the authors.
“These results indicate that the umami taste sensation is very important to the maintenance of good health in the elderly.”
Published online, open access, doi: 10.1186/2044-7248-4-10
“The important role of umami taste in oral and overall health”
Authors: Takashi Sasano, Shizuko Satoh-Kuriwada and Noriaki Shoji