P ART I Nutritional Concerns of Athletes
CHAPTER 5 CHAPTER 5 Nutritional Concerns of Elderly Athletes
II. OVERLYING CHARACTERISTICS OF THE ELDERLY A. Physiological Aspects
1. Body Composition and Muscular Strength
Aging brings about many changes in physical condition. Among these changes, body fat increases,19 at the expense of muscle and bone, both of which decrease.17 Most of the body fat increase accumulates in the abdominal area.19 With a decrease in muscle (or lean body mass), which is more metabolically active tissue, the body uses fewer calories to function and thus the basal metabolic rate of the elderly is lower.20 The decline in resting metabolic rate is also attributed to other factors including Na-K pump activity, increasing fat mass, lower maximal aerobic power, and menopausal status.21 Total energy needs also decrease concomitant with a decline in energy expenditure due to decreased physical activity. If caloric intake is not reduced, weight gain may occur.
As one ages, total body composition changes due to the decrease in fat-free mass and increasing body fat.20 Sedentary elders have a higher body fat percentage than their active peers,22 and there is some evidence that those with a high percent body fat have high levels of disability.23 While total body weight may not change with aging, loss of muscle is usually great. An increase in body fat tends to equal the weight that is lost from a decrease in muscle mass.
By controlling energy intake and exercising, the elderly can maintain the same body fat levels as much younger individuals.24 Regular aerobic or endurance exercise produces fat loss in this population;25 however, the amount lost is not enough to completely balance aging-associated body composition changes. A dual-component program of aerobic and strength training is needed to preserve lean body mass25,26 and to increase the metabolism of endogenous fat stores.27 Fat oxidation, in general, is lower in the elderly than in younger adults,27,28 but can be increased after endurance training with no significant changes in lipolysis or free fatty acid availability during exercise.27
Positive benefits are associated with exercise for the elderly29 and include increased muscle strength. A decrease in muscle strength, as occurs with aging, is one of the major causes of disability.20 For example, decreases in walking and chair-rising speeds are associated with a decrease in strength.30 Even small increases in muscle strength in the elderly can slow functional decline and provide a better quality of life.31 The decrease in mobility and physical performance as one ages is directly linked to loss of muscle mass.32-34 This is attributed to the combined loss from both types of muscle fibers, but especially from type II fibers.30,35 Reduced muscle fiber size also occurs with aging. A decline in muscle mass begins after age 30, becoming more exaggerated after the age of 50.36-38 Muscle strength, however, usually does not differ dramatically until approximately age 70, when reduced contractile strength of muscle becomes evident.36,39,40
Resistance training helps to lessen the normal muscle loss and loss of muscle strength that are associated with aging.41-43 With strength training, it is possible to substantially increase both upper- and lower-body strength while also increasing total fat-free mass and decreasing total fat mass by the same amount.44
Dietary supplements are often prescribed for elderly and/or rehabilitation patients in need of weight gain. When combined with a program of strength training, the supplements might influence increases in lean and adipose tissues without affecting strength gain,45 but by themselves, multi- nutrient supplements are not effective in counteracting muscle weakness and frailty among the very elderly.46 Likewise, neither chromium picolinate nor creatine monohydrate, both popular supple- ments among athletes, enhances muscle size or power development,47 muscle strength or lean body mass accretion,47,48 or endurance48 in older men participating in resistance training.
At or around age 65, muscle mass is about 80% of what it was at age 20, with the loss occurring in the lower extremities more quickly than in the upper extremities.49 As well, muscle strength begins to decline rapidly after approximately age 50.50 However, the elderly are able to regain
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strength as easily as younger people,51 and regular exercise may also ameliorate age-related dis- eases.52 The strength gain comes, not from changes in muscle mass, but from an increased ability to recruit more muscle units and fibers as well as a possible increase in neural activation.53,54 Aging- associated body composition changes are also very similar to those that occur with certain diseases:
exercise, nutrition, vascular and neurologic abnormalities, and hormones all have effects similar to those of aging on body composition changes.55
Age-specific formulae and tables should be used when determining body composition of older adults.56 Because stature decreases with increasing age, height should be measured rather than taken from self-reports.1 In elderly women, there are several differences among health-related factors based on the level of physical activity, including body weight and body mass index, flexibility of the hip and spine, and endurance.57
Obesity is common among the elderly58,59 until the age of approximately 75 years, after which it occurs less often.60 Many diseases, including myocardial infarction, stroke, hypertension, hyper- lipidemia, and diabetes, as well as overall mortality, are associated with obesity.61-63 Obese elderly should be encouraged to make dietary and lifestyle changes, to include reducing total fat intake (i.e., balancing the dietary energy profile), avoiding micronutrient deficiencies, and increasing intake of dietary fiber.60 Energy balance is more likely among women and fat loss is less significant.64 2. Cardiovascular Functions
Heart disease is the number one cause of death for those aged 65 years and over.65 Age-related changes in the healthy heart include cellular hypertrophy and increased impedance to left ventricular ejection,66 decreased maximal heart rate due to reduced contractility of the myocardium,52,67 and increased systolic blood pressure.68 Arterial function and structure also change with age, showing increasing vascular stiffness and accumulations of lipids, collagen, and minerals.69 Finally, the ability of the muscles to use oxygen declines 8–10% per decade, and most of this decrease is due to inactivity.17 Fortunately, regular exercise may reduce the rate of this decline.29,31,70-72
There is enough evidence to support an inverse correlation between physical activity and heart disease to influence public health policy regarding lifelong physical activity and physical fit- ness.18,29,73-76 Atherosclerosis, too, is influenced by exercise-induced metabolic changes,77-81 as is hypertension.82-86 Whereas earlier reports of the benefits of regular exercise in preventing heart disease rarely included women or non-white individuals, several recent papers have extended our understanding,87-89 although more studies are needed, especially concerning racial and ethnic differences.87,90,91
3. Bone Health
Dietary calcium and vitamin D are important to bone fracture risk, especially among women, who may have poor mineral and vitamin intakes, and to the elderly, who may suffer decreased mineral and vitamin absorption.92 A decline in calcium absorption is a normal consequence of aging,93 beginning at approximately age 60 for women and age 70 for men.94 This decrease in absorption is associated with low calcium intake, hypercalciuria, and decreased blood levels of 1,25-dihydroxy vitamin D,93 and can eventually lead to osteoporosis and bone fractures. There are also seasonal differences in vitamin D levels and bone mineral density in northern-latitude- dwelling elderly women,95 and overt vitamin D deficiency has been implicated as a contributing factor of syndrome X (in which degenerative vascular disease increases with glucose intolerance and diabetes).96
Gender, hormonal status, heredity, and calcium and vitamin D intake influence bone mass, which declines 5–10% per decade after age 40;93 up to 6% per year after menopause.97 More than 30% of women over age 65 will develop spinal fractures due to age-related loss of bone density,
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and the number of total fractures among Americans is expected to rise substantially in the next 50 years.17 An awareness of adequate dietary calcium and its role in the prevention of osteoporosis has received continuing emphasis in the literature of nutrition.98-101
Physical activity is important in the prevention of hip fractures,102 whereas physical inactivity has been noted as a significant risk factor for the occurrence of hip fractures and possibly osteoporo- sis.101,103 High-intensity strength training for postmenopausal women has a protective effect on bone density and improves muscle mass and strength.98,102,104-106 Continued resistance exercise increases bone mass and reverses the loss of skeletal calcium in the elderly,92,106-108 and aerobic exercise may similarly affect bone density.109 Elderly athletes would do well to exercise in moderation, however, using a well-planned regimen after consulting with a physician, for there is some evidence to indicate that endurance athletes may suffer an uncoupling of bone cell metabolism and consequent loss of bone density.110,111
Falls occur with increasing frequency as aging progresses, in both men112,113 and women.114-116 Regular exercise, by increasing strength and balance, may reduce the risk of falling.92,100,102,108
Lifelong regular exercise has become part of the prescription for reducing age-related loss of bone mass.29,117,118 Even patients with osteoarthritis, which is often associated with obesity, can exercise if they focus on lower intensity, longer duration activities that place less impact on the joints.119 These may be simple, job-related activities120 or more leisurely pursuits.29,105
4. Gastrointestinal and Alimentary Functions
By itself, aging has no significant adverse effects on caloric intake and nutritional status of healthy elderly individuals.121 Although many physiological factors can affect these two parameters, overall gastrointestinal function remains largely unchanged by aging.122 However, specific gas- trointestinal parameters may show age-related changes in some elderly individuals, such as a slowing of gastric emptying time,123 an increase in esophageal (e.g., reflux disease)124 and colonic (diarrhea, irritable bowel syndrome, constipation, etc.) disorders,124,125 changes in intestinal absorp- tion,122,126-130 decreased insulin production and sensitivity,131-133 and, perhaps most important, a loss of reserve capacity, which may compromise gastrointestinal function during periods of stress.134 Some of these can be partially overcome or prevented by exercise.52
Several other age-related physical and physiological changes have the potential to compromise nutrition in some individuals. Many will lose some or all of their natural teeth as they age, conditions that may be associated with lower than recommended intakes for some important nutrients.135,136 Difficulty chewing food is a logical consequence of tooth loss, occurring even if the missing teeth are replaced with dentures, and may lead to patterns of food avoidance and dietary inadequacies.137 The sense of smell seems to decrease with age, but there is limited information addressing the mechanisms of this aging-related sensory loss. Most researchers agree, however, that perceived aging-related loss of taste is actually a function of olfactory ability.138-142 Sensory-specific satiety, i.e., a decrease in the perceived pleasantness of a food as it is consumed, may change with age and may be entirely absent in people over the age of 65.143,144 More research is needed to determine whether, as one ages, observed declines in olfactory ability, appetite, and hunger, together with perceived decline in tasting ability, are linked to inactivity and/or other physical or psychosocial variables.121
Research concerning the effects of exercise on gastrointestinal function is relatively recent, although infrequent observations have been made since William Beaumont’s landmark studies over 100 years ago.145 What seems clear is that the gastrointestinal tract functions optimally at rest, that both upper and lower gastrointestinal disorders can occur with even moderate exercise, and that female exercisers seem to be more affected by digestive maladies than male exercisers.146-151 Wise athletes of any age would do well to develop an individualized regimen to minimize or eliminate their specific gastrointestinal discomfort(s) when exercising.
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