1999 Volume 3 Issue 1 Pages 3-9
The sensory mechanism for recognizing the amount of food in the oral cavity and the ability to determine the optimal amount of food to be swallowed are of prime importance to effectively control the functions of food intake and swallowing． Unfortunately， no studies have been conducted in this field．Fujishima et al．first examined these functions in those with dysphagia and normal volunteers to make a comparative study． ln the present study we modified their examination method to perform a more detailed investigation and to understand the sensory mechanism involved in food intake and the ability to determine the amount of food to be swallowed． The number of subjects was increased to allow a reliable statistical analysis． Although Fujishima et al． used jelly as the test food， we used solid food to examine the difference in the physical properties of test food． The subjects studied included 36 healthy female students． At first we measured 10.0 ml of water and gave it to the subjects so that they could memorize the exact amount of water． Then the subjects were asked to measure the standard amount of water with their mouths five times at intervals of one to two minutes． We increased the amount of water up to 20.0 ml and repeated the same experiment． The average amounts of water intake were 10.6 ± 0.86 ml in the first experiment and 20.2 ± 1.45 ml in the second experiment (mean ± SD)．In order to determine the optimal volume to be swallowed， we selected rice crackers as experimental solid food and gave them to the subjects． These rice crackers were uniform in size and weight． The number of rice crackers was gradually increased so that the subjects could recognize how many rice crackers they could chew in their oral cavity without difficulty． The subjects made a subjective evaluation of the changes of their swallowing functions． As results of these experiments which were repeated three times， we recognized that the optimal weight of rice crackers was 1.1 g on the average and that the optimal amount to be swallowed was stable because no subjects reported any change in their swallowing functions．Although the optimal amount to be swallowed was slightly correlated with the height（r ＝0.402， p＜0.05）, correlation with body weight and body mass index was negligible．The present study demonstrated that normal volunteers had excellent ability to recognize the exactamount of food in their oral cavities． We discussed the factors to determine the optimal amount of solid food to be swallowed．
