Young rats are more gourmets than old
Remy’s palate might be exquisite in Pixar’s Ratatouille (2007), but it may decline as he ages, according to a recent report published in Neurosciences Letter.
Japanese researchers from Kagoshima University studied the effect of aging on umami sensation in a rat model. But before we go any further, what is umami? In addition to the classical four basic tastes (sweet, bitter, sour, and salty), we perceive the fifth element – umami, a Japanese word for pleasant, savory taste. We taste umami through glutamate, which can be found in natural food sources, such as fish, cured meats, mushrooms, and some vegetables. Many of us are also familiar with the unnatural source, monosodium glutamate (MSG), which is often used as a food additive to enhance the flavor.
In the study, the researchers subjected rats aged 5-12 weeks (equivalent to human teenagers) and 21-22 months (equivalent to middle-aged humans) to a two-bottle preference test. Two water bottles were placed side by side: one containing flavorless water and another holding water with one of the five basic tastes. The researchers report that younger rats showed strong preference toward umami-flavored water (containing MSG or similar additives) than tasteless water, whereas older rats showed no preference. This preference was unique to umami taste, as there was no difference in the preferences among the four other tastes between the two age groups, the researchers say.
Subsequent tests on the activities of the rats’ taste nerves indicated that both young and old rats produce robust responses toward umami taste, so that umami sensation is carried to the brain regardless of age. Thus, the researchers conclude that the loss of preference toward umami in aged rats is likely caused by the changes in the brain associated with aging. In their words, “In conclusion, this is the first report indicating the existence of aging effects on the modification of umami preference in the [central nervous system].”
The researchers hope their study lends clues to appetite and eating patterns induced by taste and aging. They comment that further experiments are necessary to identify mechanisms that caused the loss of umami preference in aged rats.
Lastly, for those of you who have no clue about the reference I made at the beginning, Ratatouille (2007) is a computer-animated comedy starring a youthful rat Remy, who dreams of becoming a Parisian chef.