The ability to taste umami in food could have an effect on overall health, particularly in older people, Japanese researchers suggest.
Sweet, salty, sour, bitter and umami are the five basic tastes.
In a small study, taste tests revealed that elderly patients who had lost their taste for umami also complained of appetite and weight loss.
Boosting saliva flow in their mouths appeared to stimulate their taste buds and improve their eating habits.
Umami is a Japanese word, meaning delicious and savoury, which has been shown to be distinct from saltiness.
It is found in foods that contain high levels of glutamate, such as cured meats, shellfish, soy sauce, cheese and green tea, and other foods rich in protein.
Writing in the journal Flavour, scientists from Tohoku University Graduate School of Dentistry in Japan developed an umami taste sensitivity test and used it on 44 patients.
Those who had problems tasting umami complained that food was no longer palatable and they were not eating normally.
All of the patients were aged over 65 so their loss of taste could be due to aging, the study said.
But the researchers also suggested that diseases suffered by elderly patients and side effects from their medications could cause reduced salivation, leading to taste disorders.
They found that giving them kelp tea (made of seaweed) helped to get saliva flowing and that in turn had a positive effect on their taste sensations.
The increase in saliva from the umami taste was "long-lasting", whereas the increase in saliva after stimulation with a sour taste "diminished immediately", the study said.
"The sense of umami taste promotes salivary secretion, and saliva strongly influences oral functions such as taste senation.
"Thus, umami taste function seems to play an important role in the maintenance of oral and overall health."
Umami taste receptors are thought to exist in the gut as well which means they may also play a part in digestion.