Nutritional Strategies to Combat Type 2 Diabetes in Aging Adults: The Importance of Protein

Abstract

The prevalence of pre-diabetes (PD) and type II diabetes (T2D) has risen dramatically in recent years affecting an estimated 422 million adults worldwide. The risk of T2D increases with age, with the sharpest rise in diagnosis occurring after age 40. With age, there is also a progressive decline in muscle mass starting after the age of 30. The decline in muscle mass and function due to aging is termed sarcopenia and immediately precedes the sharp rise in T2D. The purpose of the current review is to discuss the role of protein to attenuate declines in muscle mass and insulin sensitivity to prevent T2D and sarcopenia in aging adults. The current recommended dietary allowance for protein consumption is set at 0.8 g/kg/day and is based on dated studies on young healthy men and may not be sufficient for older adults. Protein consumption upwards of 1.0-1.5 g/kg/day in older adults is able to induce improvements in glycemic control and muscle mass. Obesity, particularly central or visceral obesity is a major risk factor in the development of PD and T2D. However, the tissue composition of weight loss in older adults includes both lean body mass and fat mass and therefore may have adverse metabolic consequences in older adults who are already at a high risk of lean body mass loss. High protein diets have the ability to increase weight loss while preserving lean body mass therefore inducing "high-quality weight loss," which provides favorable metabolic changes in older adults. High protein diets also induce beneficial outcomes on glycemic markers due to satiety, lowered post-prandial glucose response, increased thermogenesis, and the ability to decrease rates of muscle protein breakdown (MPB). The consumption of dairy specific protein consumption has also been shown to improve insulin sensitivity by improving body composition, enhancing insulin release, accelerating fat oxidation, and stimulating rates of muscle protein synthesis (MPS) in older adults. Exercise, specifically resistance training, also works synergistically to attenuate the progression of PD and T2D by further stimulating rates of MPS thereby increasing muscle mass and inducing favorable changes in glycemic control independent of lean body mass increases.

Keywords: aging; dairy; protein; resistance exercise; sarcopenia; type 2 diabetes.

Figure 1

Insulin resistance and anabolic resistance are the hallmarks of aging and can exacerbate the increased risk of sarcopenia and type 2 diabetes. Insulin resistance results in a lower ability to decrease muscle protein breakdown in the fed state, which can lead to loss of muscle mass, contributing to development of sarcopenia. Older adults have anabolic resistance, which leads to decrease in muscle protein synthesis in the fed state, which overtime leads to muscle mass loss. Lower muscle mass will lower glucose storage capacity, which in turn can increase the risk of type 2 diabetes.

Figure 2

Interrelated effects of increased protein consumption on factors related to both sarcopenia and type II diabetes in older adults.