| Co-Investigator(Kenkyū-buntansha) |
KOMAI Michio Tohoku University, Fac. of Agriculture, Associate Researcher, 農学部, 助手 (80143022)
FURUKAWA Yuji Tohoku University, Fac. of Agriculture, Professor, 農学部, 教授 (60005626)
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| Research Abstract |
In order to solve the mechanism of the relationship between nutrition and food preference we have studied on the effects of protein, zinc nutrition balance which determines food preference by changing the gustation nerve responses.
The preference to salt and to alcohol were changed by source and levels of dietary protein. Low levels of dietary protein induces reduction of gustation nerve responses in 5 basic tastes and rats become to take in salty and bitter solutions which they do not prefer usually, since their gustation became insensitive. In contrary, preference of alcohol was reduced in rats fed low protein level diets, since the nerve response of alcohol was increased. Also capsaicin, the pungent component of red pepper, reduced preference to salt by changing protein level in diet. These results suggest that the changes of food preference is due to the gustation nerve responses affected by protein nutrition.
It has been said that zinc is also an important factor which affects gustation, since it is essential to maintain structure of gustational receptor and it is important to take in zinc as a coenzyme. We have found that the preference of NaCl solution and carbonated water becomes greater in zinc deficient rats. The activity of zinc requiring enzyme, carbonic anhydrase of tongue epithelium and glandula submandibulare was reduced in zinc deficient rats. Also, the preference of bitter solution rose nearly to 50% in rats which activity of alkaliphosphatase (also a zinc requiring enzyme) was reduced. Since the chorda tympani nerve sensitivity to NaCl solutions did not change at all, on the other hand, a remarkable decrease of lingual trigeminal nerve sensitivity to carbonated water was seen in zinc deficient rats, zinc deficiency might change the lingual trigeminal nerve sensitivity to carbonated water possibly via carbonic anhydrase activity.
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