Nutritional Aspects Of Aging

Volume 1

Linda H. Chen

• Publisher: CRC Press
• Year: 2018
• Print ISBN: 9781315896038
• eBook ISBN: 9781351092036
• Edition: 1
• Topic: Medicine
• Subtopic: Nutrition, Dietics & Bariatrics

The first section in Volume 1 describes the fundamentals of nutrition and aging which include research strategies for the study of nutrition and aging. The nutritional modulation of the aging process which has provided a major breakthrough in the field of nutrition and longevity is also discussed. These include biomedical influences, and social and psychological aspects. Section 3 includes dietary characteristics of the elderly population and methods for the assessment of nutritional status. The nutritional status of the elderly with respect to individual nutrients as determined by dietary survey and by biochemical methods is described in Section 4. Section 4 also includes discussion on nutrient metabolism, requirements, nutritional imbalances, and deficiencies of nutrients. Energy metabolism and obesity as a factor in pathogenesis of diseases are also discussed.

Section IV
Nutrient Metabolism, Requirements, Nutritional Status, Imbalance, and Deficiencies

Chapter 7
Energy

Loren G. Lipson and George A. Bray

Table of Contents

1. I. Introduction
2. II. Energy Homeostasis: General Considerations
3. III. Energy Homeostasis in the Elderly
   1. A. Factors Influencing Energy Intake
   2. B. Changes in Body Composition with Age
   3. C. Changes in Energy Utilization with Age
4. IV. Obesity and Aging
5. V. The Hyperglycemia of Aging
6. VI. Therapeutic Interventions
7. References

I. Introduction

The energy needs of an individual vary according to the person's metabolic rate, size, sex, activity, physical environment, hormonal balance, and age. With increasing age there are marked changes in man's energy consumption and requirements. Age-associated factors in the elderly influence energy intake and lead to alterations in body composition and general energy needs. It is the purpose of this chapter to examine energy requirements of the elderly population, to investigate some special problems in energetics and metabolism involving the aging process, and to formulate a rational approach to meet the energy requirements in our senior citizens.

II. Energy Homeostasis: General Considerations

Energy homeostasis requires a dynamic balance between nutrient intake and energy expenditure. This complex series of processes begins with the intake of nutrients which are physically and chemically acted upon and transported into various body compartments and then into the cells of these various compartments under the control and regulation of hormonal and neural stimuli. These stimuli are governed in part by the level of nutrient intake. When intake is low, these stimuli act to mobilize the energy which is stored in the body in the form of fat, protein, and carbohydrate. These fuels are metabolized to produce the energy for mechanical work and to maintain the basal metabolic rate (functions such as maintaining constant internal temperature, intracellular environment, and the mechanical processes such as respiration and cardiac function which sustain the body at rest).¹

Adenosine triphosphate (ATP) is the principal intermediate for energy transfer in the body. Its energy is contained in the high-energy terminal phosphate bond, which can be coupled to biochemical or physical processes and results in the formation of adenosine diphosphate (ADP) or adenosine monophosphate (AMP). These latter compounds may be regenerated to ATP by oxidative phosphorylation. The net result of this process is the consumption of oxygen and fuel and the production of ATP, water, and carbon dioxide. By the process of fuel combustion, two thirds of the energy is released as heat and the other one third is trapped in the terminal phosphate bond of ATP.¹ (See Figure 1.)

In normal man, there is a large endogenous fuel reservoir made up primarily of fat, which accounts for about 85% of the energy reserve (135,000 kcal).² Protein stores account for 24,000 kcal (primarily in muscle), while glycogen stores account for only 1200 kcal. These stored fuels can be utilized when nutrient intake is low in order to maintain the basal metabolic rate and to regenerate ATP stores. Triglycerides from the diet or stored in adipose tissue yield fatty acids and glycerol. The latter may be converted back to glucose in the liver or muscle and fatty acids can be metabolized to or, in conditions of insulin deficiency, converted by the liver to ketone bodies.¹ Protein from muscle or other body sources or from food sources is broken down to amino acids; stored glycogen and ingested polysaccharides may be converted to glucose. These key metabolites are further metabolized to produce ATP, heat, water, and carbon dioxide. Some amino acids may enter the Krebs cycle directly and the resulting released ammonia is converted to urea in the liver; other amino acids, glucose, and lactate are first converted into pyruvate and then to acetyl coenzyme A, which is also the product of metabolism of fatty acids and ketone bodies.¹ Thus, changes in the body composition and organ function may have profound changes on energy homeostasis. Regulatory processes by which food intake is coupled to energy needs are not fully understood, but changes in food availability, eating behavior, emotional outlook, and taste perception may influence energy h...

Table of contents

• Cover
• Title
• Copyright
• PREFACE
• THE EDITOR
• CONTRIBUTORS
• Contents
• SECTION I: FUNDAMENTALS OF NUTRITION AND AGING
• SECTION II: IMPACT OF AGING ON NUTRITIONAL STATUS
• SECTION III: ASSESSMENT OF NUTRITIONAL STATUS
• SECTION IV: NUTRIENT METABOLISM, REQUIREMENTS, NUTRITIONAL STATUS, IMBALANCE, AND DEFICIENCIES
• Index