Eating rate, oral processing, gastric emptying and appetite in older adults: Investigations of food intake and food form

研究背景众所周知，口腔加工行为会影响预期的饱腹感、能量摄入量和餐后饱腹感(1-3)。在健康的年轻人中，人们已经确定，吃得慢会导致食物摄入量减少，反之，吃得快会导致摄入量增加(3)。对于老年人来说，吃得慢可能不利于满足充足的卡路里和蛋白质需求，但对于确保舒适和安全的吞咽是必要的(4，5)。众所周知，咀嚼会影响食物的颗粒大小(7)，颗粒越小，从胃里排空的速度就越快，也更容易消化和吸收营养。唾液流率较高的人需要较少的咀嚼周期和较少的口腔时间(7)。牙列问题和肌肉力量减弱，再加上唾液流量减少，可能会阻碍许多老年人的食物摄取(9)，要求他们咀嚼更长时间，以获得适合吞咽的丸剂成分。这可能带来的后果是，进食率降低，食物摄入量减少。某些食物已被证明可以刺激唾液分泌，如果在饭前食用，可能会使进食变得更容易。个体的口腔加工有相当大的差异(1，6)，然而，到目前为止，大多数研究都规定了固定的咀嚼制度，以确定咀嚼对食物摄入量的影响。人们对自然咀嚼模式对食物摄入量的影响以及通过食物途径操纵口腔加工的可能性知之甚少。我们假设通过控制食物来促进唾液流动和帮助咀嚼会增加老年人的进食率和食物摄入量。该项目旨在：(1)评估食物的口腔加工对老年人食物摄入量的影响(2)探索食物形式和食物呈现的操纵对口腔加工和食物摄入的影响。研究1将评估牙列、进食率和口腔加工对老年人(70岁)主观饱足感的影响。测量的食物大小，吞咽，食物在嘴里的时间，进食率，每一口的咀嚼和总的活跃进食时间将包括在内。参与者将被要求在一顿测试餐之前和之后每隔15分钟对他们的饱腹感进行评级。胃排空将使用13C-醋酸钠呼气试验进行评估。血糖和血浆胰岛素的测量将从手指抽血样本中进行。将评估口腔容量、刺激和非刺激唾液流率。一口标准的食物将被咀嚼到吞咽的程度，然后被吐出，这将被用来确定唾液是否被食物吸收以及唾液淀粉酶的产生。将测量天然牙齿的数量/假牙的存在(11)以及咀嚼能力(12)。研究2将评估食物形式的差异以及对口腔加工和食物摄入的影响。在两个测试日中，将对呈现为两种不同形式(固体和泥)的单一食物进行评估，以确定咀嚼对老年人饱腹感和食物摄入量的影响。将使用与研究1类似的方法，以及在最初的测试餐后4小时提供的临时餐来评估对饱食感的影响。研究3将评估添加可能刺激唾液产生的食物。这可能会使老年人更容易进食，并减少在口腔中所需的时间，以确保食物足够柔软以供吞咽，从而提高进食率。

BackgroundOral processing behaviours are known to impact on expected fullness, energy intake and post-meal satiety (1-3). In healthy young adults, it is established that slower eating results in a lower food intake and conversely eating quickly results in higher intakes (3). For older adults, slower eating may be detrimental to meeting adequate calorie and protein needs but necessary to ensure comfortable and safe swallowing (4,5). Mastication is known to impact on the particle size of the food (7), the smaller the particle size, the faster it will be to emptying from the stomach (8), making it also easier to digest and absorb the nutrients. People with greater salivary flow rates have been shown to require fewer chewing cycles and less time in the mouth (7). Dentition problems and reduced muscle strength, alongside reduced salivary flow, can hinder food intake for many older people (9) requiring them to chew for a longer period of time in order to achieve a bolus composition suitable for swallowing. The likely consequences of this, are slower eating rates and reduced food intake. Certain foods have been shown to stimulate salivary production (10) and could make eating easier if consumed prior to a meal. There is considerable variation in the oral processing of individuals (1,6), however the majority of research to date has prescribed a fixed chewing regime to ascertain the impact of chewing on food intake. Considerably less is known about the impact of natural chewing patterns on food intake and the potential to manipulate oral processing through food approaches. We hypothesise that manipulating foods to enhance saliva flow and aid mastication will increase eating rate and food intake in older adults.The project aims to:(1) Assess the extent of oral processing of food on food intake in older adults (2) Explore the impact of manipulation of food form and food presentation on oral processing and food intake.Study 1 will evaluate the effect of dentition, eating rate and oral processing on subjective satiety in older adults (aged >70 years of age). Measurement of bitesize, swallowing, time of food in the mouth, eating rate, chews per bite and total active eating time will be included. Participants will be asked to rate their satiety prior to, and at 15-minute intervals after, a test meal. Gastric emptying will be assessed using the 13C-sodium acetate breath test. Measurements of blood glucose and plasma insulin will be taken from fingerprick blood samples. Oral volume capacity, stimulated and unstimulated salivary flow rates will be assessed. A standardised mouthful of food will be chewed to the point of swallowing and then expectorated, this will be used to ascertain saliva uptake into food as well as salivary amylase production. Measurement of numbers of natural teeth / presence of dentures will be undertaken (11) as well as a measure of masticatory ability (12).Study 2 will evaluate difference in food form and the impact on oral processing and food intake. Across two test days a single food presented in two different forms (solid and puree) will be assessed to ascertain the impact of mastication on satiety and food intake in older adults. Similar methods to Study 1 will be used, as well as an ad libitum meal provided 4 hours after the initial test meal to assess the impact on satiety.Study 3 will evaluate the addition of foods that have the potential to stimulate saliva production. This may make eating easier for older adults and decrease the time required in the mouth to ensure sufficient softness of food for swallowing, hence increasing eating rate.