Dietary protein and change in physical function in black and white older adults

描述(由申请人提供)：预计到2030年，老年人的数量将翻一番。随着老年人口的增长，与年龄相关的身体机能下降的负担也会增加。观察数据显示，老年人的功能能力差异很大，并确定了几个潜在的可修改因素，影响功能衰退的风险。虽然营养在延缓或预防慢性病方面的作用已经得到了很好的证实，但由于缺乏对老年人营养和饮食的大型前瞻性研究，人们对营养在维持健康状况中的作用知之甚少。 身体机能。尽管如此，越来越多的证据表明，营养因素对维持身体机能很重要。随着年龄的增长，瘦体重的减少，以及与之相关的力量的下降，都有很好的文献记载，并部分解释了与年龄相关的身体功能的丧失。膳食蛋白质不足被认为可能是导致瘦体重、力量和身体功能随年龄增长而下降的一个因素。国家数据显示，相当大比例的老年人蛋白质摄入量不足。此外，目前的膳食蛋白质需求主要是基于对年轻人的短期氮平衡研究，可能低估了最佳地保持老年人的瘦体重、力量或身体功能所需的摄入量。我们建议使用来自Health ABC研究的数据，在6年的随访中检查饮食蛋白质摄入量与力量变化和客观和主观测量的身体功能之间的关系。自1997-98年来，每年都会对3075名70多岁的黑人和白人男性和女性进行前瞻性队列跟踪调查。将解决以下具体目标：1)确定饮食蛋白质摄入量是否预测力量和体能表现的变化；2)确定饮食蛋白质摄入量是否预测活动受限事件。我们假设，在6年的随访中，与蛋白质摄入量较低的参与者相比，蛋白质摄入量较高的参与者在力量和体能方面的下降较小，活动受限的风险也较低。在探索性分析中，我们还将研究蛋白质来源(例如动物和蔬菜)和必需氨基酸摄入量(特别是支链氨基酸，如赖氨酸)和身体机能变化之间的关系~饮食蛋白质摄入量和身体机能之间的联系是否通过瘦体重的变化而调节~蛋白质和身体机能之间的联系是否被其他危险因素(例如，身体不活动、肥胖、体重减轻、炎症和胰岛素抵抗)改变~以及饮食蛋白质摄入量和身体机能之间的关联是否因种族而异或有助于解释身体机能的种族差异。拟议的分析将确定饮食蛋白质在维持老年人身体机能方面的作用，并提供关于在老龄化人口中维持身体机能的最佳蛋白质摄入量水平的饮食建议。

DESCRIPTION (provided by applicant): The number of older adults is expected to double by 2030. With the growth of the older population comes a parallel expectation of growth in the burden of age-related declines in physical function. Observational data show wide variations in the functional capabilities of older adults and have identified several potentially modifiable factors that influence the risk of functional decline. While the role of nutrition is well-establised in delaying or preventing chronic disease, because of the lack of large prospective studies of nutrition and diet in older adults, less is known about the role of nutrition in the maintenance of physical function. Nonetheless, increasing evidence suggests that nutritional factors are important to the maintenance of physical function. Loss of lean mass with aging, and the associated declines in strength, are well documented and partially account for aging-related loss of physical function. Inadequate dietary protein has been suggested as a factor that may contribute to the declines in lean mass, strength, and physical function that occurs with age. National data suggest that a significant proportion of older adults consume inadequate protein. Furthermore, current dietary protein requirements are based predominately on short-term nitrogen balance studies in young adults and may underestimate the intakes needed to optimally preserve lean mass, strength, or physical function in older adults. We propose to examine the association between dietary protein intake and change in strength and both objectively and subjectively measured physical function over 6 years of follow-up using data from the Health ABC study, a prospective cohort of 3,075 black and white men and women in their seventies who have been followed annually since 1997-98. The following specific aims will be addressed: 1) to determine whether dietary protein intake predicts change in strength and physical performance~ and 2) to determine whether dietary protein intake predicts incident mobility limitation. We hypothesize that participants with higher intakes of protein will have smaller declines in strength and physical performance and a decreased risk of incident mobility limitation over 6 years of follow-up compared to those with lower intakes of protein. In exploratory analyses, we will also examine the association between protein source (e.g., animal vs. vegetable) and essential amino acid intake (particularly branched chain amino acids such as leonine) and change in physical function~ whether the associations between dietary protein intake and physical function are mediated through changes in lean mass~ whether the associations between protein and physical function are modified by other risk factors (e.g., physical inactivity, obesity, weight loss, inflammation, and insulin resistance)~ and whether the associations between dietary protein intake and physical function differ by race or help explain racial disparities in physical function. The proposed analyses will determine the role of dietary protein in the maintenance of physical function in older adults and inform dietary recommendations regarding the level of optimal protein intake for the maintenance of physical function in an aging population.