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The book also includes appendices that list nutrient recommendations for dle-aged adults established by three major organizations: the Institute of Medicine, National Academy of Sciences

Nutrition and Exercise Concerns

of Middle Age

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Library of Congress Cataloging‑in‑Publication Data

Nutrition and exercise concerns of middle age / editor, Judy A Driskell.

p cm.

Includes bibliographical references and index.

ISBN 978‑1‑4200‑6601‑2 (alk paper)

1 Middle‑aged persons‑‑Nutrition 2 Exercise for middle‑aged persons I

Driskell, Judy A (Judy Anne)

This book is dedicated to the experts who wrote the included chapters.

Contents

Preface xiThe Editor xiiiContributors xv

Chapter Fat-Soluble Vitamins 111

Maria Stacewicz-Sapuntzakis and Gayatri Borthakur

Chapter 0 Trace Elements Excluding Iron—Chromium and Zinc 233

Henry C Lukaski and Angus G Scrimgeour

Chapter 2 Caffeine and Tannins 269

Jay Kandiah and Valerie A Amend

1

Chapter 3 Herbal Supplements 283

Jidong Sun and David W Giraud

VI

SectIon I Recreational Activities

1

Chapter 4 Endurance Training 317

Shawn R Simonson and Catherine G Ratzin-Jackson

1

Chapter 5 Resistance Training 353

Robert J Moffatt, Jacob M Wilson, and Tait Lawrence

Contents ix

VII

1

Chapter 6 Cardiovascular Issues 397

Susan Hazels Mitmesser

1

Chapter 7 Cancer 415

Farid E Ahmed

Appendices 457

Preface

The scientific and lay media extol the health benefits of good nutrition and physical activity Most books that have been published about nutrition and physical activity have dealt with nutritional needs of young adults who exercise vigorously At around

30 years of age or so, individuals start to become more concerned about having and maintaining good health and realizing the personal benefits of good nutrition and moderate-intensity physical activity Some health professionals seem to believe that nutrition and physical activity information is the same for all people What consti-tutes good nutrition and exercise habits is generally not interpreted for middle-aged individuals Middle age is considered to be around 30 to 60 years of age Middle-aged individuals most often are not involved in collegiate or professional sports but frequently do exercise on a regular basis as a form of recreation Middle-aged adults are concerned about obtaining and maintaining good health and how they can reduce their risk of chronic diseases

This volume includes a collection of chapters written by scientists from several academic disciplines who have expertise in an area of nutrition or kinesiology as it relates to exercise and sport The introductory chapter on nutrition and exercise con-cerns of middle age is followed by chapters on the energy-yielding nutrients (carbo-hydrates, lipids, and proteins), three chapters on the vitamins (fat-soluble vitamins, vitamin C, and B-vitamins), three chapters on the minerals (major minerals, iron, and trace elements excluding iron) A chapter is included on fluids, electrolytes, and hydration Chapters are included on the commonly consumed substances caffeine and tannins as well as herbal supplements Two chapters describe resistance training and endurance training relating these to nutrient intakes, exercise recommendations, and overall health The age-related chronic diseases cardiovascular disorders and cancer are discussed in relation to nutrition and exercise

The book also includes appendices that list nutrient recommendations for dle-aged adults established by three major organizations: the Institute of Medicine, National Academy of Sciences for those living in the United States and Canada; the National Health and Medical Council (Australia and New Zealand Government for those living in Australia and New Zealand); and the World Health Organization The daily values for vitamins and minerals are also listed

mid-Sports nutritionists, sports medicine and fitness professionals, researchers, coaches, trainers, physicians, dietitians, nurses, athletes, students, and the well-informed layperson will find this book to be informative and timely It discusses

“cutting edge” research on the topics of nutrition and exercise

Judy A Driskell, Ph.D., R.D.

Professor, University of Nebraska

The Editor

Judy Anne Driskell, Ph.D., R.D is Professor of Nutritional Science and Dietetics

at the University of Nebraska She received her B.S degree in Biology from the University of Southern Mississippi in Hattiesburg Her M.S and Ph.D degrees were obtained from Purdue University She has served in research and teaching positions

at Auburn University, Florida State University, Virginia Polytechnic Institute and State University, and the University of Nebraska She has also served as the Nutrition Scientist for the U.S Department of Agriculture/Cooperative State Research Service and as a Professor of Nutrition and Food Science at Gadjah Mada and Bogor Universities in Indonesia

Dr Driskell is a member of numerous professional organizations including the American Society of Nutritional Sciences, the American College of Sports Medicine, the International Society of Sports Nutrition, the Institute of Food Technologists, and the American Dietetic Association In 1993 she received the Professional Scientist Award of the Food Science and Human Nutrition Section of the Southern Association of Agricultural Scientists In addition, she was the 1987 recipient of the Borden Award for Research in Applied Fundamental Knowledge of Human Nutrition She is listed as an expert in B-Complex Vitamins by the Vitamin Nutrition Information Service

Dr Driskell co-edited the CRC book Sports Nutrition: Minerals and Electrolytes with Constance V Kies In addition, she authored the textbook Sports Nutrition and co-authored the advanced nutrition book Nutrition: Chemistry and Biology, both pub- lished by CRC She co-edited Sports Nutrition: Vitamins and Trace Elements, first

all with Ira Wolinsky She also edited the book Sports Nutrition: Fats and Proteins,

published by CRC Press She has published more than 160 refereed research cles and 16 book chapters as well as several publications intended for lay audiences and has given numerous presentations to professional and lay groups Her current research interests center around vitamin metabolism and requirements, including the interrelationships between exercise and water-soluble vitamin requirements

Contributors

Farid E Ahmed, Ph.D.

GEM Tox Consultants and Labs, Inc

Greenville, North Carolina

Department of Kinesiology and Health

Georgia State University

Nutrition and Applied Clinical Research

Miami Research AssociatesSouth Miami, Florida

Hamilton, Ontario, Canada

George U Liepa, Ph.D., F.A.C.N.

School of Health Sciences

Eastern Michigan University

Ypsilanti, Michigan

Henry C Lukaski, Ph.D.

Grand Forks Human Nutrition Research

Center

U.S Department of Agriculture,

Agricultural Research Service

Grand Forks, North Dakota

Susan Hazels Mitmesser, Ph.D.

Mead Johnson Nutrition

U.S Department of Agriculture,

Agricultural Research Center

Grand Forks, North Dakota

Heather E Rasmussen, Ph.D., R.D.

Department of Nutrition and Health Sciences

University of NebraskaLincoln, Nebraska

Catherine G Ratzin-Jackson, Ph.D.

Department of KinesiologyFresno State UniversityFresno, California

Herb E Schellhorn, Ph.D.

Department of BiologyMcMaster UniversityHamilton, Ontario, Canada

Angus G Scrimgeour, Ph.D.

Military Nutrition DivisionU.S Army Research Institute for Environmental MedicineNatick, Massachusetts

Shawn R Simonson, Ed.D., C.S.C.S., A.C.S.M., H.F.S.

Department of KinesiologyBoise State UniversityBoise, Idaho

Brian S Snyder, M.S.

Department of Human NutritionKansas State University

Manhattan, Kansas

I Section

Introduction

Nutrition and Exercise

Concerns of Middle Age

Judy A Driskell

I INTRODUCTION

Middle-aged adults should have good nutritional and exercise habits These habits influence their physical performance as well as their overall health The American College of Sports Medicine, American Dietetic Association, and Dietitians of Canada issued a joint position statement on nutrition and athletic performance in 2000.1–3 The key points of this joint position statement are given in Table 1.1 These key points sum-marize the current energy, nutrient, and fluid recommendations for physically active adults and competitive athletes These recommendations would also apply to physi-cally active middle-aged adults This position statement is intended to provide guid-ance to health professionals working with physically active adults and is not intended for use with children or adolescents It is currently being updated The updated ver-sion, once it is available, can be accessed via the websites of these organizations According to the World Health Organization (WHO), about 30% of deaths in the world in 1999 were due to cardiovascular diseases, and this percentage is expected

to increase.4 One of the main objectives of the WHO’s global strategy for the preven-tion and control of noncommunicable diseases is to reduce exposure in an integrated manner to the major risk factors of tobacco use, unhealthy diet, and physical inactiv-ity Unhealthy diets and physical inactivity are a problem to populations worldwide

CONTENTS

I Introduction 3

II Definition of Middle Age 5

III Energy Balance 6

IV Nutrient Recommendations 8

V Dietary Guidelines 13

VI Food Guidance Recommendations 16

VII Exercise Recommendations 16

VIII Conclusions 20

References 20

4 Nutrition and Exercise Concerns of Middle Age

TABLE 1.1

Key Points of the Joint Position Statement of the American College of Sports Medicine, American Dietetic Association, and Dietitians of Canada

on Nutrition and Athletic Performance

During times of high-intensity training, adequate energy needs to be consumed to maintain body

•

weight, maximize the training effects, and maintain health Low-energy intakes can result in loss

of muscle mass, menstrual dysfunction, loss or failure to gain body density, and increased risk of fatigue, injury, and illness.

Body weight and composition can affect exercise performance but should not be used as the sole

•

criterion for participation in sports; daily weigh-ins are discouraged Optimal body-fat levels vary depending upon the sex, age, and heredity of the athlete, as well as the sport itself Body-fat assessment techniques have inherent variability, thus limiting the precision with which they can

be interpreted If weight loss (fat loss) is desired, it should start early—before the competitive season—and involve a trained health and nutrition professional.

Protein requirements are slightly increased in highly active people Protein recommendations for

•

endurance athletes are 1.2 to 1.4 g/kg body weight per day, whereas those for resistance and strength-trained athletes may be as high as 1.6 to 1.7 g/kg body weight per day These

recommended protein intakes can generally be met through diet alone, without the use of protein

or amino acid supplements, if energy intake is adequate to maintain body weight.

Fat intake should not be resisted, because there is no performance benefit in consuming a diet

•

with less than 15% of energy from fat, compared with 20% to 25% of energy from fat Fat is important in the diets of athletes as it provides energy, fat-soluble vitamins, and essential fatty acids Additionally, there is no scientific basis on which to recommend high-fat diets to athletes The athletes at greatest risk of micronutrient deficiencies are those who restrict energy intake or

•

use severe weight-loss practices, eliminate one or more food groups from their diet, or consume high-carbohydrate diets with low micronutrient density Athletes should strive to consume diets that provide at least the RDAs/DRIs for all micronutrients from food.

Dehydration decreases exercise performance; thus, adequate fluid before, during, and after

•

exercise is necessary for health and optimal performance Athletes should drink enough fluid to balance their fluid losses Two hours before exercise 400 to 600 mL (14 to 22 oz) of fluid should

be consumed, and during exercise 150 to 350 mL (5 to 12 oz) of fluid should be consumed every

15 to 20 minutes depending on tolerance After exercise the athlete should drink adequate fluids

to replace sweat losses during exercise The athlete needs to drink at least 450 to 675 mL (16 to

24 oz) of fluid for every pound (0.5 kg) of body weight lost during exercise.

Before exercise, a meal or snack should provide sufficient fluid to maintain hydration, be

•

relatively low in fat and fiber to facilitate gastric emptying and minimize gastrointestinal distress,

be relatively high in carbohydrate to maximize maintenance of blood glucose, be moderate in protein, and be composed of foods familiar and well tolerated by the athlete.

During exercise, the primary goals for nutrient consumption are to replace fluid losses and

•

provide carbohydrate (approximately 30 to 60 g per hour) for the maintenance of blood glucose levels These nutrition guidelines are especially important for endurance events lasting longer than an hour, when the athlete has not consumed adequate food or fluid before exercise, or if the athlete is exercising in an extreme environment (heat, cold, or altitude).

Introduction: 5

II DEFINITION OF MIDDLE AGE

Exactly what is middle age? Simply stated, middle age is the period of life between young adulthood and old age The idea that midlife or middle age is a separate and distinct life stage is a cultural conception that originated in the 20th century.5 The emergence of middle age as a life stage is linked to the increase in longevity and the decrease in fertility.6 Little research has been conducted on the middle aged, espe-cially with regard to nutrition and exercise

Middle age is better defined by a pattern of characteristics as opposed to logical age Generally by middle age, adults are expected to have established a family

chrono-of their own, have found a clear career direction, and have taken on responsibility with respect to their children, their aging parents, and sometimes their community.7

Many physiological changes occur during aging Aging is a gradual process Many of the physiological changes that usually occur in healthy individuals dur-ing middle age are given in Table 1.2 Good nutrition and exercise practices can moderate the effects of aging on the body’s physiological functioning Caloric restriction may slow some of the changes that occur in aging.8 Conclusive evi-dence indicates that endurance and strength training generally slow some of the age-related changes.8–11 The chapters in this book discuss how good nutrition and exercise practices are beneficial to the health status of individuals, particularly dur-ing middle age

After exercise, the dietary goal is to provide adequate energy and carbohydrates to replace

•

muscle glycogen and to ensure rapid recovery If an athlete is glycogen-depleted after exercise, a carbohydrate intake of 1.5 g/kg body weight during the first 30 minutes and again every 2 hours for 4 to 6 hours will be adequate to replace glycogen stores Protein consumed after exercise will provide amino acids for the building and repair of muscle tissue Therefore, athletes should consume a mixed meal providing carbohydrates, protein, and fat soon after a strenuous

competition or training session.

In general, no vitamin and mineral supplements should be required if an athlete is consuming

•

adequate energy from a variety of foods to maintain body weight Supplementation

recommendations unrelated to exercise—such as folic acid in women of childbearing potential— should be followed If an athlete is dieting, eliminating foods or food groups, is sick or

recovering from injury, or has a specific micronutrient deficiency, a multivitamin/mineral supplement may be appropriate No single nutrient supplements should be used without a specific medical or nutritional reason (e.g., iron supplements to reverse iron deficiency anemia) Athletes should be counseled regarding the use of ergogenic aids, which should be used with

Sources: American College of Sports Medicine, Joint position statement: nutrition and athletic

perfor-mance, Med Sci Sports Exerc 32, 2130–45, 2000.1 Used with the permission of Wolters Kluwer Health.

RDAs = Recommended Dietary Allowances; DRIs = Dietary Reference Intakes.

6 Nutrition and Exercise Concerns of Middle Age

Some researchers, governmental agencies, and others have utilized chronological age in designating the middle years of adulthood These designations vary from 40

to 65 years,12 35 to 54 years,13 25 to 75 years,14 40 to 60 years,15 and 31 to 50 years.16

No consensus exists regarding the entry and exit points of middle age

III ENERGY BALANCE

Energy balance in individuals depends on their energy intakes as well as their energy outputs The majority of the population in the United States consumes more food energy than they expend, primarily because they are sedentary Data from the 2006 National Health Interview Survey indicates that 35% of adults 18 years of age and older in the United States were overweight (but not obese) and 26% were obese.17

Sixty-two percent of adults included in the survey reported not participating in any type of vigorous leisure-time physical activity This is also true in other developed countries, though in some developing countries, most of the population consumes too little food energy In the United States, food energy is expressed as calories

Lung function gradually declines after age 20 10

A decrease in height begins at around age 25 in men and 20 in women 8

Loss of muscle mass begins around age 30 9

The number and size of muscle fibers progressively decrease, beginning when individuals are in their 30s; this results in a decrease in skeletal muscle mass and lean body mass 10

A modest increase in the size of the heart occurs from age 20 to 80 8

Plasma endothelin-1 concentration, which is produced by vascular endothelial cells and has been implicated in regulation of vascular tonus and progression of atherosclerosis, was higher in healthy middle aged women (31–47 years) than in healthy young women (21–28 years) 11

Intellectual abilities peak during the 30s and plateau through the 50s and 60s 10

Renal blood flow progressively decreases at age 30 to 40 years to age 80 10

Bone density begins to decrease between ages 40 and 50 in both genders, but most rapidly in

women 10

The abilities to taste and smell start to gradually diminish when people are in their 50s 9

Adapted from: Masoro, E.J., Challenges of Biological Aging, Springer, New York, 1999;8 Beers, M.H

and Jones, T.V., Eds., The Merck Manual of Health & Aging, Merck Research Laboratories,

Whitehouse Station, NJ, 2005; 9 Beers, M.H and Berkow, R., Eds., The Merck Manual of Geriatrics, 3rd ed., Merck Research Laboratories, Whitehouse Station, NJ, 2006; 10 Maeda S

et al., Aerobic exercise training reduces plasma endothelin-1 concentration in older women,

J Appl Physiol. 96, 336–41, 2003 11

Introduction: 7

(properly referred to as kilocalories), while some other countries express food energy

as kilojoules; one calorie is equal to 4.186 kilojoules18 or 4.18 kilojoules.19

The three major components of energy expenditure are basal metabolism (though sometimes resting metabolism is utilized), thermic effect of food (previously known

as specific dynamic action), and physical activity (also known as thermic effect of exercise and as energy expenditure of physical activity) All three of these compo-nents decrease as one ages, with a more rapid decline occurring around 40 years of age in men and 50 years of age in women.20,21

The Institute of Medicine, National Academy of Sciences, uses the term Estimated Energy Requirement (EER) which is the average dietary intake predicted to main-tain energy balance in a healthy adult of a certain gender, age, weight, height, and level of physical activity that is consistent with good health.18 The formula for calcu-lating the EER for men 19 years of age and older is given below:

EER = 662 – (9.53 x age [y]) + PA x (15.91 x weight [kg] + 539.6 x height [m])The physical activity coefficient (PA) for men is 1.00 for those who are sedentary; 1.11, for low active; 1.25, for active; and 1.48, for very active The formula for calcu-lating the EER for women 19 years of age and older is given below:

EER = 354 – (6.91 x age [y]) + PA x (9.36 x weight [kg] + 726 x height [m])The PA for women is 1.00 for those who are sedentary; 1.12, low active; 1.27, active; and 1.45, very active

Individuals who take 30 minutes of moderately intense activity (such as walking

2 miles in 30 minutes) or an equivalent amount of physical exertion in addition to activities involved in maintaining a sedentary lifestyle have a physical activity level (PAL) of about 1.5 and are classified as low active PALs of ≥1.0–<1.4 are classified

as sedentary, ≥1.4–<1.6 as low active, ≥1.6–<1.9 as active, and ≥1.9–<2.5 as very active.18 Total energy expenditure (TEE) predictive equations were also developed

by the Institute of Medicine (IOM), National Academy of Sciences18 for use in mating body weight maintenance in normal weight, overweight, and obese adults The National Institutes of Health (NIH)22 in the United States and the World Health Organization (WHO)23 utilized body mass index (BMI as kg/m2) in defining these body weight categories BMIs <18.5 are considered underweight, 18.5 to 24.99 as healthy or desirable body weight, 25 to 29.99 as overweight, and ≥30 as obese Total daily expenditures as calculated from TEE equations for normal weight, overweight, and obese men and women intended for use for those living in the United States and Canada18 are given in Tables 1.3 and 1.4

esti-The group responsible for establishing the nutrient recommendations for Australia and New Zealand EERs of adults using predicted basal metabolic rate (BMR) multi-plied by PAL, with PAL values varying from 1.2 to 2.2 PAL values of 1.75 and above are consistent with good health while values below 1.4 are incompatible with mov-ing around freely or earning a living.19 To determine maintenance or actual energy requirements (EERM), an individual’s current body weight is utilized In determin-ing desirable estimated energy requirements (DEER), the current body weight is used

8 Nutrition and Exercise Concerns of Middle Age

if it is within the healthy weight range (BMI between 18.5 and 24.99), but if the BMI

is ≥25, the desirable body weight is determined by assuming a BMI of 22 The EER,

in megajoules, using predicted BMR multiplied by PAL are intended for use by men and women living in Australia and New Zealand are given in Table 1.5 The estimated total energy recommendations of Australia and New Zealand for men and women approximate those of the United States and Canada, though slightly different terms are used and the recommendations are given in a different unit of measurement.Energy expenditure is discussed in greater detail in chapters 14 and 15 of this book Detailed information on energy balance is also available in references 18 and

19 of this chapter, several chapters in the books Energy-Yielding Macronutrients and

obe-sity on energy expenditure

IV NUTRIENT RECOMMENDATIONS

Water is the largest single constituent of the body The IOM established an Adequate Intake (AI) for total water (from drinking water, beverages, and foods) based on the

a For each year above 30, subtract 10 kcal/d from TEE.

b PAL = physical activity level PAL = ≥1.0<1.4, sedentary; ≥1.4<1.6, low active; ≥1.6<1.9, active;

≥1.9<2.5, very active.

In that scientific evidence suggests that individuals can consume moderate levels

of the energy-yielding macronutrients carbohydrates, lipids (fats), and protein out risk of adverse health effects, increased risk may occur with chronic consump-tion of diets that are too high or too low in each of these macronutrients Much of this

a For each year above 30, subtract 7 kcal/d from TEE

b PAL = physical activity level PAL =≥ 1.0<1.4, sedentary; ≥1.4<1.6, low active; ≥1.6<1.9, active;

≥1.9<2.5, very active.

10 Nutrition and Exercise Concerns of Middle Age

evidence is based on associations of high or low intakes of these macronutrients with risks of coronary heart disease, cancer, diabetes, and obesity Hence, the IOM estab-lished Acceptable Macronutrient Distribution Ranges (AMDR) intended for use by healthy individuals in the United States and Canada The AMDR is given as a range

of intakes for a food energy source that is associated with reduced risk of chronic disease yet ensuring sufficient intakes of essential nutrients The AMDRs for adults are as follows: carbohydrates, 45–65% of calories (not more than 25% of calories from added sugars); lipids, 20–35% of calories (0.6–1.2% of calories from α-linolenic acid and 5–10% of calories from linoleic acid); and protein, 10–35% of calories.18

The Australian National Health and Medical Research Council in conjunction with the New Zealand Ministry of Health, while establishing Nutrient Reference Values

in 2006 reviewed and discussed the AMDRs intended for use by United States and Canadian healthy populations but did not set any for use by their populations.19

The IOM16 has established a set of reference nutrient intake values called Dietary Reference Intakes (DRIs) intended for use with the healthy populations in the United

TABLE 1.5

Estimated Energy Requirements (MJ/d) of Men and Women using

Predicted Basal Metabolic Rate (BMR) Multiplied by Physical Activity Level (PAL) for Men and Women Living in Australia and New Zealand

BMI = 22 a Physical activity level (PAL) b

Adapted from: Australian National Health and Medical Research Council and New Zealand Ministry of

Health, Nutrient Reference Values for Australia and New Zealand, Available at: http://www.

Introduction: 11

States and Canada The DRIs encompass the Estimated Average Requirements (EARs), Recommended Dietary Allowances (RDAs), Adequate Intakes (AIs), and Tolerable Upper Intake Levels (ULs) These terms are defined in Table 1.6 The RDAs and the AIs are the values intended for use in guiding individuals to achieve adequate nutrient intakes.16,28 The uses of the DRIs for healthy individuals and groups

as given by the IOM16,28 are given in Table 1.7

Healthy middle-age adults living in the United States and Canada should consume

at least the RDA or AI for a nutrient but not more than the UL The RDAs or AIs for the essential nutrients for individuals 31 to 70 years of age are given in Appendices A–C and the ULs are given in Appendices D and E.16,18,26,29–31

The group responsible for establishing the nutrient recommendations for Australia and New Zealand decided to adopt the approach of the United States/Canada DRIs but to vary some of the terminology.19 Their Nutrient Reference Values included EARs, Recommended Dietary Intakes (RDIs; similar to the United States/Canadian Recommended Dietary Allowances or RDAs), AIs, and Upper Levels of Intake (ULs; similar to the Tolerable Upper Intake Levels or ULs of the United States and Canada) The RDIs, AIs, and ULs for healthy adults living in Australia and New Zealand are given in Appendices F–J Many of the numerical values of the Australia/New Zealand Nutrient Reference Values are similar to those of the United States and Canada, though some are slightly different Likely the small differences that exist

in these recommendations are influenced by the fact that different experts served on the two groups that established the recommendations Several other countries have

TABLE 1.6

Categories of Dietary Reference Intakes

Estimated Average Requirement (EAR) The daily intake value estimated to meet the

nutrient requirement of 50% of the healthy individuals in a life stage/gender group.

Recommended Dietary Allowance (RDA) The average daily dietary nutrient intake

sufficient to meet the needs of 97–98% of healthy individuals in a life stage/gender group.

The RDA is calculated from the EAR.

Adequate Intake (AI) The daily nutrient intake or approximation of

observed mean intakes by a group(s) of healthy individuals in a life stage/gender group.

The daily nutrient intake calculated when scientific evidence is not available to calculate

an EAR.

Tolerable Upper Intake Level (UL) The highest daily nutrient intake that is likely to

pose no risk of adverse health for almost all individuals in a life stage/gender group.

Adapted from: Institute of Medicine, National Academy of Sciences, Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride, National Academies Press, Washington, DC, 1997 16

12 Nutrition and Exercise Concerns of Middle Age

established nutrient recommendations for their populations The Recommended Nutrient Intakes of Vitamins and Minerals for adults established by the WHO32 are given in Appendices K and L

Some evidence exists that athletes and others who are vigorously active may efit from the consumption of larger amounts of some of the vitamins and minerals than from the amounts recommended for the general public in the same lifestage (gender/age) groupings The following suggestions come from the IOM:

ben-Because of the functioning of niacin in the oxidation of fuel molecules at least

a 10% adjustment should be be made to reflect differences in the average energy utilization and body sizes of individuals who exercise vigorously.29

Those spending much time training for active sports may require additional thiamin and those who are ordinarily physically active may require more riboflavin.29

Those who exercise vigorously may need more of the antioxidant nutrients vitamin A, carotenoids, vitamin E, and vitamin C.30

Potassium can be lost, primarily via sweat, during heat exposure and cise; however, it is not known how much the intake should be increased to compensate for this loss

exer-TABLE 1.7

Uses of the Dietary Reference Intakes in Evaluating Nutrient Intakes

Allowance

Usual intake at or higher than this level has a low probability of being inadequate.

Not utilized in evaluating intakes of groups.

Adequate Intake Usual intake at or higher than

this level has a low probability of being inadequate.

Mean usual intake or higher than this level implies a low prevalence of inadequate intakes However, this assessment is made with less confidence when not based

on mean intakes of healthy people.

Tolerable Upper Intake Level Usual intake higher than this

level may put the individual

at risk of adverse effects from excessive intake of the nutrient.

Utilized in estimating the percentage of the population

at potential risk of adverse effects from excessive intakes

of the nutrient.

Adapted from: Institute of Medicine, Dietary Reference Intakes: Applications in Dietary Assessment,

National Academies Press, Washington, DC, 2002/2005 28

Introduction: 13

Individuals who exercise strenuously in the heat on a daily basis can lose substantial amounts of sodium (along with chloride), but it has not been ascertained how much The United States Army Research Institute of Environmental Medicine (USARIEM) estimated sodium and water losses

at four levels of energy expenditure (1900, 2400, 2900, and 3600 kcal daily) This report estimated the daily sodium requirements at average day-time dry bulb temperatures varying from 59–104 ºF to be as follows: 1900 kcal/d, ~1600–4020 mg sodium/d; 2400 kcal/d, ~2000–6200 mg sodium/d;

2900 kcal/d, ~2500–7500 mg sodium/d; and 3600 kcal/d, ~3020–9600 mg sodium/d This USARIEM model is an empirical model that includes an equation to predict sweating rate during work.26

The vitamin and mineral needs of middle-aged individuals who exercise moderately

or vigorously are discussed in more detail in Chapters 5–10

The contents of specific nutrients in processed foods must be placed on the uct label in the United States Specific nutrient content information may also be provided for nonprocessed foods, but it is not mandatory The term Daily Value

prod-is used in stating the nutrient content of processed foods and dietary supplements

in the United States The Daily Value is not the same as the RDA However, the Daily Values were developed utilizing the 196833 and the 197434 RDAs The Daily Values include Daily Reference Values (DRVs) and Reference Daily Intakes (RDIs) DRVs have been established for fat (meaning total fat), saturated fat, carbohydrates (including fiber), protein, cholesterol, sodium, and potassium RDIs have been established for most of the vitamins and essential minerals The Daily Values35 for adults and children 4 or more years of age, based on a 2,000-calorie diet, are given

in Appendix M

V DIETARY GUIDELINES

The Department of Health and Human Services (HHS) and the Department

of Agriculture (USDA) have developed Dietary Guidelines for Americans36

(Table 1.8) These guidelines are intended for use by healthy individuals 2 years

of age and above The Dietary Guidelines for Australian adults37 are given in

Table 1.9 The dietary guidelines for the United States and for Australia are rather similar, although those for the United States are more detailed Both the United States and Australia update their dietary guidelines on a regular basis Several other countries also have developed dietary guidelines for use by individuals living

in their countries

Some health organizations have also developed dietary guidelines and these are updated from time to time For example, the American Heart Association Dietary Guidelines38 are currently available online at http://www.americanheart.org/presenter.jhtml?identifier=4561 The World Cancer Research Fund in conjunction with the American Institute for Cancer Research39 in 2007 made eight basic dietary recom-mendations expected to reduce the incidence of cancer and issued personal recommen-dations for each of the eight These recommendations are given in Appendix N The

14 Nutrition and Exercise Concerns of Middle Age

TABLE 1.8

Dietary Guidelines for Americans, Key Recommendations

Adequate Nutrients Within Calorie Needs

Consume a variety of nutrient-dense foods and beverages within and among the basis food groups

•

while choosing foods that limit the intake of saturated and trans fats, cholesterol, added sugars,

salt, and alcohol.

Meet recommended intakes within energy needs by adopting a balanced eating pattern, such as the

well-being, and a healthy body weight.

– To reduce the risk of chronic disease in adulthood: Engage in at least 30 minutes of intensity physical activity, above usual activity, at work or home on most days of the week – For most people greater health benefits can be obtained by engaging in physical activity of more vigorous intensity or longer duration.

moderate-– To help manage body weight and prevent gradual, unhealthy body weight gain in adulthood: Engage in approximately 60 minutes of moderate- to vigorous-intensity activity on most days

of the week while not exceeding caloric intake requirements.

– To sustain weight loss in adulthood: Participate in at least 60 to 90 minutes of daily intensity physical activity while not exceeding caloric intake requirements Some people may need to consult with a healthcare provider before participating in this level of activity.

moderate-Achieve physical fitness by including cardiovascular conditioning, stretching exercises for

•

flexibility, and resistance exercises or calisthenics for muscle strength and endurance.

Food Groups To Encourage

Consume a sufficient amount of fruits and vegetables while staying within energy needs Two cups

Introduction: 15

Fats

Consume less than 10 percent of calories from saturated fatty acids and less than 300 mg/day of

•

cholesterol, and keep trans fatty acid consumption as low as possible.

Keep total fat intake between 20 and 35 percent of calories, with most fats coming from sources of

•

polyunsaturated and monounsaturated fatty acids, such as fish, nuts, and vegetable oils.

When selecting and preparing meat, poultry, dry beans, and milk or milk products, make choices

•

that are lean, low-fat, or fat-free.

Limit intake of fats and oils high in saturated and/or

such fats and oils.

amounts suggested by the USDA Food Guide and the DASH Eating Plan.

Reduce the incidence of dental caries by practicing good oral hygiene and consuming sugar- and

•

starch-containing foods and beverages less frequently.

Sodium and Potassium

Consume less than 2,300 mg (approximately 1 teaspoon of salt) of sodium per day.

Alcoholic beverages should be avoided by individuals engaging in activities that require attention,

16 Nutrition and Exercise Concerns of Middle Age

recommendations made by these health organizations are rather similar to those of the Dietary Guidelines for Americans36 and the Dietary Guidelines for Australian adults.37

VI FOOD GUIDANCE RECOMMENDATIONS

The USDA and HHS have developed a food guidance system known as MyPyramid.40

MyPyramid is given in Figure 1.1 and can be viewed in more detail and utilized at

http://www.MyPyramid.gov The pyramid is intended for use by healthy individuals

2 years of age and above The pyramid gives the amount of foods from the various food groups that one should consume (Figure 1.2) People can use the pyramid web-site in evaluating their diets and their physical activity Some other countries have also developed food guidance systems for their populations

VII EXERCISE RECOMMENDATIONS

In June, 1998 the ACSM issued a position stand entitled “The Recommended Quantity and Quality of Exercise for Developing and Maintaining Cardiorespiratory and Muscular Fitness and Flexibility in Healthy Adults.”41 This position stand will likely be updated soon, and readers are encouraged to check the organization’s web-site for the update These recommendations are for healthy adults who are not ath-letes These recommendations are summarized in Table 1.10 After seeking advice of

TABLE 1.9

Dietary Guidelines for Australian Adults

Enjoy a wide variety of nutritious foods

Eat plenty of vegetables, legumes and fruits

and take care to

Limit saturated fat and moderate total fat intake

Prevent weight gain: be physically active and eat according to your energy needs

Care for your food: prepare and store it safely

Encourage and support breastfeeding

Taken from: National Health and Medical Research Council, Australian Government, Dietary Guidelines for all Australians, 2003 Available at http://www.nhmrc.gov.au/publications/synopses/diet- syn.htm 3

Introduction: 17

those invited to a workshop planned by the Food and Nutrition Board, IOM, and the Board on Population Health and Public Health Practice, the USDA and HHS consid-ered developing a comprehensive set of physical activity guidelines for Americans.42

These Physical Activity Guidelines for Americans43 were recently released and the Key Guidelines for Physical Activity for Adults are given in Table 1.11

VIII CONCLUSIONS

Nutrition and exercise influence the physical performance of individuals of all ages, including middle-aged adults Experts do not agree as to when middle age begins or ends In this book, middle age is considered to be around 30 to 60 years of age.Many individuals, particularly those living in developed countries, consume more food energy than they expend, primarily because they are sedentary Individuals who exercise vigorously need to consume more food energy because they expend more energy Maintaining energy balance is of great importance to athletes, as it has been shown to influence physical performance

Athletes and nonathletes need to always be hydrated as this influences their physical performance as well as their health Acceptable macronutrient distribution ranges have been established for the energy-yielding macronutrients carbohydrates, lipids (fats), and proteins The recommended intakes of vitamins and minerals for individuals living in the United States and Canada,16,26,29–31 in Australia and New Zealand,19 and those given by the WHO32 are detailed in Appendices A–L in the back of this book

Dietary guidelines have been established for Americans36 and for Australians,37

as well as those living in several other countries These guidelines are intended for use by both athletes and nonathletes

Exercise recommendations, particularly those of the ACSM,41 are given Chapters 14

and 15 of this book discuss in detail the benefits of resistance and endurance training.Little is known regarding the relationships among nutrition, exercise, and health during middle age Additional research is needed on this topic, as the middle aged are a substantial portion of the population

FIGURE 1.1 MyPyramid (U.S Department of Agriculture Available at http://www.

mypyramid.gov/ 40 )

USDA is an equal opportunity provider and employer.

Eat at least 3 oz of

whole-grain cereals, breads,

crackers, rice, or pasta

every day

1 oz is about 1 slice of

bread, about 1 cup of

breakfast cereal, or ½ cup

of cooked rice, cereal,

or pasta

Eat more dark-green veggies like broccoli, spinach, and other dark leafy greens Eat more orange vegetables like carrots and sweetpotatoes Eat more dry beans and peas like pinto beans, kidney beans, and lentils

Eat a variety of fruit Choose fresh, frozen, canned, or dried fruit

Go easy on fruit juices

Go low-fat or fat-free when you choose milk, yogurt, and other milk products

If you don’t or can’t consume milk, choose lactose-free products or other calcium sources such as fortified foods and beverages

Choose low-fat or lean meats and poultry Bake it, broil it, or grill it Vary your protein routine — choose more fish, beans, peas, nuts, and seeds

For a 2,000-calorie diet, you need the amounts below from each food group To find the amounts that are right for you, go to MyPyramid.gov.

Eat 6 oz every day Eat 2½ cups every day Eat 2 cups every day Get 3 cups every day;for kids aged 2 to 8, it’s 2 Eat 5½ oz every day

Find your balance between food and physical activity Know the limits on fats, sugars, and salt (sodium)

Be sure to stay within your daily calorie needs.

Be physically active for at least 30 minutes most days of the week.

About 60 minutes a day of physical activity may be needed to prevent weight gain.

For sustaining weight loss, at least 60 to 90 minutes a day of physical activity may be required.

Children and teenagers should be physically active for 60 minutes every day or most days.

Make most of your fat sources from fish, nuts, and vegetable oils.

Limit solid fats like butter, stick, margarine, shortening, and lard, as well as foods that contain these

Check the Nutrition Facts label to keep saturated fats, trans fats, and sodium low.

Choose food and beverages low in added sugars Added sugars contribute calories with few, if any, nutrients.

Make half your grains whole Vary your veggies Focus on fruits Get your calcium-rich foods Go lean with protein

U.S Department of Agriculture Center for Nutrition Policy and Promotion

April 2005 CNPP-15

FIGURE 1.2 Food group comments for MyPyramid (U.S Department of Agriculture Available at http://www.mypyramid.gov/.40 )

Introduction: 19

REFERENCES

1 American College of Sports Medicine, Joint position statement: Nutrition and athletic

performance, Med Sci Sports Exerc 32, 2130–45, 2000.

2 American Dietetic Association, Joint position statement: Nutrition and athletic

perfor-mance, J Am Diet Assoc 100, 1543–56, 2000.

3 Dietitians of Canada, Joint position statement: Nutrition and athletic performance, Can

J Diet Prac Res 61, 176–92, 2000.

4 World Health Organization, Diet, Physical Activity and Health: Report by the Secretariat, 55th World Health Assembly, Document WHA55/16, March 27, 2002.

5 Skolnick, A., Embattled Paradise, Basic, New York, 1991.

6 Moen P and Wethington, E., Midlife development is a life course context, in Life in the Middle, Willis, S.L and Reid, J.D., Eds., Academic Press, San Diego, CA, 1999, chap 1.

7 Staudinger, U.M and Bluck, S., A view on midlife development from life-span theory,

in Handbook of Midlife Development, Lachman, M.E., Ed., John Wiley & Sons, New

For Cardiorespiratory Fitness and Body Composition

Duration of training:

•

20 to 60 minutes of continuous or intermittent aerobic activity The intermittent activity should

be for 10 minutes or more time periods during the day The 20 to 60 minutes is dependent on the activity’s intensity.

Mode of activity:

•

Any activity that utilizes the large muscle groups and is maintained continuously.

For Muscular Strength and Endurance, Body Composition, and Flexibility

Resistance training:

•

One repetition of 8-10 exercises that trains the major muscle groups 2 to 3 days weekly

Additional repetitions may provide greater benefits.

Flexibility training:

•

Flexibility exercises sufficient to develop and maintain range of motion 2 to 3 days weekly.

Adapted from: Pollock, M.L., Gaesser, G.A., Butcher, J.D., Després, J.P., Dishman, R.K., Franklin, B.A and Garber, C.E., The recommended quantity and quality of exercise for developing and maintaining cardiorespiratory and muscular fitness and flexibility in healthy adults:

American College of Sports Medicine position stand, Med Sci Sports Exerc 30, 975–91,

1998 41

20 Nutrition and Exercise Concerns of Middle Age

TABLE 1.11

Key Physical Activity Guidelines for Adults

All adults should avoid inactivity Some physical activity is better than none, and adults who participate in any amount of physical activity gain some health benefits.

• For substantial health benefits, adults should do at least 150 minutes (2 hours and 30 minutes) a week of moderate-intensity, or 75 minutes (1 hour and 15 minutes) a week of vigorous-

intensity aerobic physical activity, or an equivalent combination of moderate- and intensity aerobic activity Aerobic activity should be performed in episodes of at least 10 minutes, and preferably, it should be spread throughout the week.

vigorous-• For additional and more extensive health benefits, adults should increase their aerobic physical activity to 300 minutes (5 hours) a week of moderate-intensity, or 150 minutes a week of vigorous-intensity aerobic physical activity, or an equivalent combination of moderate- and vigorous-intensity activity Additional health benefits are gained by engaging in physical activity beyond this amount.

• Adults should also do muscle strengthening activities that are moderate- or high-intensity and involve all major muscle groups on 2 or more days a week, as these activities provide

additional health benefits.

• All adults should avoid inactivity Some physical activity is better than none, and adults who participate in any amount of physical activity gain some health benefits.

Adults should also do muscle strengthening activities that are moderate- or high-intensity and involve all major muscle groups on 2 or more days a week, as these activities provide additional health benefits.

Examples of Different Aerobic Physical Activities

Heavy gardening (continuous digging or hoeing, with heart rate increases)

Hiking uphill or with a heavy backpack.

Source: U.S Department of Health and Human Services, 2008 Physical Activity Guidelines for Americans Available at http://www.health.gov/paguidelines , accessed October 28, 2008.

Introduction: 21

9 Beers, M.H and Jones, T.V., Eds., The Merck Manual of Health & Aging, Merck

Research Laboratories, Whitehouse Station, NJ, 2005.

10 Beers, M.H and Berkow, R., Eds., The Merck Manual of Geriatrics, 3rd ed., Merck

Research Laboratories, Whitehouse Station, NJ, 2006.

11 Maeda, S., Tanabe, T., Miyauchi, T., Otsuki, T., Sugawara, J., Iemitsu, M., et al., Aerobic

exercise training reduces plasma endothelin-1 concentration in older women, J Appl Physiol. 95, 336–41, 2003.

12 Whitbourne, S.K., The physical aging process in midlife: Interactions with

psychologi-cal and sociocultural factors, in Handbook of Midlife Development, Lackman, M.E.,

Ed., John Wiley & Sons, New York, 2001, chap 4.

13 Middle Age Wikipedia, http://en.wikipedia.org/wiki/Middle_age , accessed 08/06/2008.

14 Adams, R.L Definition—When or What is Middle Age? http://www.middleage.org/ definition.shtml , accessed 08/06/2008.

15 Middle Age Britannica Encyclopedia Website, http://www.britannica.com/#search=tab

~TOPICS%2Cterm~middle%20age , accessed 08/06/2008.

16 Institute of Medicine, National Academy of Sciences, Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride National Academy Press, Washington, DC, 1997.

17 Pleis, J.R and Lethbridge-Cejku, M., Summary Health Statistics for U.S Adults: National Health Interview Survey, 2006 Vital Health Statistics Series 10, Number 235 Hyattsville, MD, National Center for Health Statistics, U.S Department of Health and Human Services, 2007.

18 Institute of Medicine, National Academy of Sciences, Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids National Academies Press, Washington, DC, 2002/2005.

19 Australian National Health and Medical Research Council and New Zealand Ministry

of Health, Nutrient Reference Values for Australia and New Zealand Available at http:// www.nrv.gov.au , posted May, 2006, accessed 08/06/2008.

20 Poehlman, E.T., Energy expenditure and requirements in aging humans, J Nutr 122,

2057–65, 1992.

21 Poehlman, E.T., Regulation of energy expenditure in aging humans, J Am Geriatr Soc

41, 552–9, 1993.

22 National Heart, Lung, and Blood Institute and National Institute of Diabetes and

Digestive and Kidney Diseases, Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults The Evidence Report, NIH Publication No 98–4083, National Institutes of Health, Bethesda, MD, 1998.

23 World Health Organization, Obesity: Preventing and Managing the Global Epidemic Report of a World Health Organization Consultation on Obesity, World Health Organization, Geneva, 1998.

24 Driskell, J.A., Wolinsky, I., Eds., Energy-Yielding Macronutrients and Energy Metabolism in Sports Nutrition, CRC Press LLC, Boca Raton, FL, 2000.

25 Wolinsky, I., Driskell, J.A., Eds., Sports Nutrition: Energy Metabolism and Exercise,

Taylor and Francis, 2008.

26 Institute of Medicine, National Academy of Sciences, Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate National Academies Press, Washington, DC, 2005.

27 Sawka, M.N., Burke, L.M., Eichner, E.R., Maughan, R.J., Montain, S.J and Stachenfeld, N.S., Exercise and fluid replacement: American College of Sports Medicine position

stand, Med Sci Sports Exer 39, 377–90, 2007.

28 Institute of Medicine, National Academy of Sciences, Dietary Reference Intakes: Applications in Dietary Assessment National Academies Press, Washington, DC, 2000.

22 Nutrition and Exercise Concerns of Middle Age

29 Institute of Medicine, National Academy of Sciences, Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B 6 , Folate, Vitamin B 12 , Pantothenic Acid, Biotin, and Choline National Academies Press, Washington, DC, 1998.

30 Institute of Medicine, National Academy of Sciences, Dietary Reference Intakes for Vitamin

C, Vitamin E, Selenium, and Carotenoids National Academies Press, Washington, DC, 2000.

31 Institute of Medicine, National Academy of Sciences, Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc National Academies Press, Washington, DC, 2001.

32 World Health Organization and Food and Agriculture Organization of the United

Nations, Vitamin and Mineral Requirements in Human Nutrition, 2nd ed., World Health

Organization, Geneva, 2004.

33 National Research Council, National Academy of Sciences, Recommended Dietary Allowances, 7th rev ed., Printing and Publishing Office of National Academy of Sciences, Washington, DC, 1968.

34 National Research Council, National Academy of Sciences, Recommended Dietary Allowances, 8th rev ed., Printing and Publishing Office of National Academy of Sciences, Washington, DC, 1974.

35 U.S Food and Drug Administration, A Food Labeling Guide: Reference Values for Nutrition Labeling Available at http://www.cfsan.fda.gov/~dms/flg–7a.html , editorial revisions June, 1999, accessed 08/06/2008.

36 U.S Departments of Agriculture and of Health and Human Services, Dietary Guidelines for Americans, 2005 Available at http://www.health.gov/dietaryguidelines/dga2005/ document , posted 2007, accessed 08/06/2008.

37 National Health and Medical Research Council of Australia, Dietary Guidelines for Australian Adults Available at http://www.nhmrc.gov.au/publications/synopses/diet- syn.htm , posted 2003, accessed 1/25/08.

38 American Heart Association Dietary Guidelines, American Heart Association Dietary Guidelines Available at http://www.americanheart.org/presenter.jhtml?identifier=4630 , posted 2007, accessed 08/06/2008.

39 World Cancer Research Fund/American Institute for Cancer Research, Food Nutrition, Physical Activity, and the Prevention of Cancer: A Global Perspective, American Institute for Cancer Research, Washington, DC, 2007.

40 U.S Departments of Agriculture and of Health and Human Services, MyPyramid Available at http://www.mypyramid.gov , posted 2005, accessed 08/06/2008.

41 Pollock, M.L., Gaesser, G.A., Butcher, J.D., Després, J.P., Dishman, R.K., Franklin, B.A and Garber, C.E., The recommended quantity and quality of exercise for develop- ing and maintaining cardiorespiratory and muscular fitness and flexibility in healthy

adults: American College of Sports Medicine position stand, Med Sci Sports Exerc 30,

975–91, 1998.

42 Food and Nutrition Board, Institute of Medicine, Adequacy of Evidence for Physical Activity Guidelines Development: Workshop Summary, National Academies Press, Washington, DC, 2007.

43 U.S Department of Health and Human Services, 2008 Physical Activity Guidelines for Americans Available at http://www.health.gov/paguidelines , posted 10/7/2008, accessed 10/28/2008.

II Section

Energy-Yielding Nutrients

high-a source of energy during exercise Chigh-arbohydrhigh-ate stores in the body high-are limited, high-and are not able to indefinitely sustain moderate- to high-intensity exercise Considerable research over the last 30 years has investigated dietary carbohydrate and methods of manipulating its intake at several key time points before, during, and after exercise This chapter will present information regarding the metabolism of carbohydrate dur-ing exercise, as well as methods for manipulating carbohydrate consumption before, during, and after training or competition with the aim of enhancing performance and recovery.

CONTENTS

I Introduction 25

II Carbohydrate Metabolism 26

A Dietary Sources of Carbohydrates 26

B Classification of Carbohydrates 26

C Digestion and Absorption 28

D Glycemic Index 29

E Carbohydrate Transportation and Storage 30

F Carbohydrate Utilization During Exercise 32III Manipulation of Carbohydrate Intake and Physical Performance 34

A Daily Training Diet 35

B Preparation for Prolonged Endurance Exercise and Competition 37

1 Carbohydrate Loading Protocols 37

2 Pre-Event Meal 38

C Carbohydrate Consumption During Exercise 39

D Carbohydrate Consumption During Recovery from Exercise 43

IV Considerations for the Middle-Aged Athlete 44

V Research Needs 46

VI Conclusions 46References 47

26 Nutrition and Exercise Concerns of Middle Age

II CARBOHYDRATE METABOLISM

A D IETARY S OURCES OF C ARBOHYDRATES

Carbohydrates, an economical and plentiful source of calories, can be found in ing amounts in a wide variety of foods The basic diet should be consistent with the recommendations for chronic disease prevention and long-term health promotion Such a diet is high in carbohydrate (>55% of total calories), low in fat (≤30% of total calories), and places a significant emphasis on a wide variety of foods.1

vary-The various recommendations made in this chapter regarding carbohydrate intake can be satisfied via consumption of a wide range of carbohydrates, depending

on personal and cultural preference Although structure and consistency are tant aspects of an athlete’s daily routine, consumption of the same carbohydrate-containing foods day in and day out can lead to a reduction in the joy of eating Incorporating traditional foods from different ethnic groups can be an excellent way

impor-of creating variety in an athlete’s diet For example, although most athletes are iar with the fact that the main carbohydrate source in Italian food is pasta-based, it should be noted that Asian food is rice- and soybean-based, Mexican food is rice- and bean-based, and South American food is tuber-, bean-, and nut-based Being largely composed of carbohydrates, food types such as these can be incorporated into the diet to promote varied and interesting carbohydrate consumption patterns A selection of common sources of dietary carbohydrate can be found in Table 2.1

famil-B C LASSIFICATION OF C ARBOHYDRATES

Carbohydrates can be classified according to several criteria, including those based

on the structure and number of sugar molecules, as well as the degree to which they induce a rise in blood glucose and insulin levels

Monosaccharides contain only one sugar molecule and include glucose, fructose, and galactose Disaccharides, which contain two sugar molecules, include sucrose, lactose, and maltose Disaccharides can be distinguished from each other based on their specific monosaccharide building blocks, with sucrose made up of glucose and fructose, lactose made up of glucose and galactose, and maltose made of two glucose molecules.Monosaccharides and disaccharides are collectively referred to as simple sugars

or carbohydrates Simple sugars, or food products containing large amounts of ple sugars, have often been referred to as “bad” carbohydrates, mostly as a method

sim-of describing the fact that they contain little additional nutritional value other than the provision of calories Simple sugars are not inherently bad, but should certainly not make up the bulk of dietary carbohydrate intake This may be especially true for sedentary or obese individuals, with studies suggesting that consumption of large amounts of rapidly absorbed sugars can predispose such individuals to chronic dis-eases such as type 2 diabetes.2–4

Polysaccharides, which include starch, fiber, and glycogen, contain many glucose units linked together and are referred to as complex carbohydrates Maltodextrins, another type of polysaccharide, are glucose polymers containing no starch or fiber and are subsequently metabolized like simple sugars Examples of simple and com-plex carbohydrates and their dietary sources can be found in Table 2.2

Carbohydrates 27

TABLE 2.1

Common Sources of Dietary Carbohydrate

Carbohydrate (g)

(Corn Flakes)

1 cup (28 g) 24 Oatmeal, cooked 1 cup (234 g) 25 Pasta, cooked 0.5 cup (70 g) 19 Potato chips 1 ounce (28 g) 15 Rice, cooked 0.5 cup (97 g) 22

Starchy vegetables Corn, cooked 0.5 cup (75 g) 15

Green peas, cooked 0.5 cup (75 g) 11 Potatoes, mashed 0.75 cup (140 g) 25

Beans/legumes Dried beans, cooked 0.5 cup (98 g) 20

Lentils, cooked 0.5 cup (98 g) 20

Chocolate milk 1 cup (245 g) 26

Yogurt, plain 1 cup (245 g) 17 Yogurt, sweetened 1 cup (245 g) 26

Sugared beverages Orange juice 0.5 cup (125 g) 13

Sports beverage (6%) 1 cup (244 g) 14 Soft drink 12 ounces (368 g) 40

Other foods Pizza, cheese, thick

crust

2 slices (142 g) 55 Pizza, cheese, thin

crust

2 slices (166 g) 46 Cheese lasagna 1 cup (250 g) 45 Chili with beans 1 cup (260 g) 22

28 Nutrition and Exercise Concerns of Middle Age

C D IGESTION AND A BSORPTION

Digestion of carbohydrates begins to a small degree in the mouth Enzymes (salivary amylases) begin the process of digestion of complex carbohydrates by initiating the breakdown of starches Chewing (mastication) is an important part of the digestive process, reducing foods to smaller-sized particles Continuing this process of size reduction, mechanical action of the stomach increases both the rate of gastric empty-ing of food from the stomach into the small intestine and the surface area of the food particles made accessible to intestinal enzymes

The majority of carbohydrate digestion and absorption occurs in the small tine After moving into the small intestine, the monosaccharides (glucose, fructose, and galactose) are absorbed directly into the blood via the capillaries within the

intes-TABLE 2.2

Classi cation of Carbohydrates

Comments Simple Carbohydrates

Monosaccharides

Glucose Also known as dextrose; found in plant foods, fruits, honey

Fructose Also known as fruit sugar; found in plant foods, fruits, honey

Galactose Product of lactose digestion

Disaccharides

Sucrose Also known as white or table sugar; composed of glucose and fructose;

used as a sweetener Lactose Composed of galactose and glucose; found in milk and dairy products Maltose Composed of two glucose molecules; product of starch digestion

Complex Carbohydrates

Polysaccharides

Amylopectin Starch; found in plant foods and grains

Amylose Starch; found in plant foods and grains

Carrageenan Soluble fiber; found in the extract of seaweed and used as food thickener and

stabilizer Cellulose Insoluble fiber; found in the bran layers of grains, seeds, edible skins, and

peels Corn Syrup Hydrolyzed starch; found in processed foods

Dextrins Starch; found in processed foods

Glycogen Animal starch; found in meat, liver

Hemicellulose Insoluble fiber; found in the bran layers of grains, seeds, edible skins, and

peels Inulin Soluble fiber; found in Jerusalem artichokes

Invert Sugar Hydrolyzed sucrose; found in processed foods

Lignin Insoluble fiber; found in plant cell walls

Pectin Soluble fiber; found in apples

Carbohydrates 29

intestinal villi Glucose (and galactose) is absorbed via numerous dent glucose transporters (SGLT-1), whereas fructose is absorbed via less numerous sodium-independent carriers Disaccharides (sucrose, lactose, and maltose) are split into their constituent monosaccharides by specific disaccharidases, which are then absorbed directly into the blood Complex carbohydrates are acted upon by pan-creatic amylase and brush border enzymes, splitting polysaccharides to monosac-charides that are then absorbed as described above The monosaccharides absorbed into the intestinal circulation are transported to the liver via the hepatic portal vein Ultimately, glucose is the end point of carbohydrate digestion and absorption regardless of whether the original compound was a polysaccharide, disaccharide, or monosaccharide

sodium-depen-Not all of the carbohydrate content of foods consumed is digested and absorbed Carbohydrate that is not absorbed may be related to the form of the food, the type of starch, or the amount of fiber present in the food Undigested and unabsorbed car-bohydrates go to the large intestine, where they are acted upon by colonic bacteria

or excreted in the feces Large amounts of indigestible carbohydrates, or excessive amounts of simple sugars consumed rapidly, may result in excessive gas production

or gastrointestinal disturbances such as cramping and diarrhea The fiber content

of carbohydrate foods, which is largely indigestible by humans, plays an important role in maintaining appropriate gastric transit, may influence the eventual glycemic response to the foods consumed, and has important long-term health implications

D G LYCEMIC I NDEX

Consumption, digestion, and absorption of carbohydrates results in a postprandial increase in blood glucose, stimulation of insulin secretion by the pancreas, and sub-sequent increase in glucose uptake by various tissues in the body The time course and magnitude of this glycemic response are highly variable with different foods, and do not follow the basic structural characterization of carbohydrates as simple

or complex For example, consumption of identical amounts of two simple sugars, the monosaccharides glucose and fructose, results in very different blood glucose responses Glucose ingestion provokes a rapid, large increase in blood glucose, which

in turn rapidly returns to baseline levels, whereas fructose consumption results in a much slower and lower glycemic response

The concept of the Glycemic Index (GI) was developed to facilitate prediction of the glycemic response to a wide variety of foods.5 The GI is a ranking based on the postprandial blood glucose response of a particular food compared with a reference food (glucose or white bread containing 50 g of carbohydrate) Test foods contain an identical amount of carbohydrate, and the blood glucose response is determined for several hours after consumption of the test food.6 Specifically, the GI is a percentage

of the area under the glucose response curve for a specific food compared with the area under the glucose response curve for the reference food.7

Extensive testing of foods has resulted in the publication of tables of glycemic indices for a wide variety of foods.8 The GI of glucose (GI = 100) and fructose (GI

= 19) clearly demonstrates the vast differences in glycemic response that can occur with the consumption of these two structurally similar monosaccharides A GI of 19