College is a time of weight gain for many students, especially freshman year. A variety of factors play into this, including the “all-you-can-eat” dining halls, late-night snacking (Figure 13-2), convenience of high-fat snack foods, drinking sugar-based beverages, refrigerators in dorm rooms, eating quickly, and reduced physical activity from sitting in classes along with studying in the library. The freshman 10 (pounds) has increased over time to the freshman 15, and many college students gain far more weight than this.

FIGURE 13-2 Late-night snacking is a common social experience in college dormitories.

Entering the workforce also alters food habits and may reduce kcalorie expenditure. Once-athletic adolescents or former military personnel who now find themselves in desk jobs 40 hours weekly may soon realize that their food habits need to change to curb weight gain.

Other changes occur to transform eating habits, from living on one’s own to eating at restaurants on dates and blending food preferences in a marriage or partnership. Social occasions contribute to overeating high-fat, high-sugar foods, some of which are entrenched in society (Figure 13-3). Becoming parents can dramatically affect mealtimes (e.g., contending with a crying baby during dinner).

FIGURE 13-3 Marriage has many influences on food choices.

If young adults were exposed to a positive meal environment throughout their own childhood, and learned to accept a variety of foods, the transitions will be easier and a positive nutritional status can still be maintained. For the young adult who has not yet learned how to accept a variety of foods, it is still possible. Just as a child needs to try a new food 10 times before a preference is developed, the same seems to hold true for adults. The fear of new foods can still be a major obstacle, but with motivation can be overcome.

HOW DO LIFE CYCLE ISSUES AFFECT NUTRITIONAL STATUS?

Various changes incurred during the early adult years will influence food habits. This includes food availability at college and work settings, new relationships with blending of food preferences, and marriage status. A study of married individuals found widowed men and women were at the greatest risk of low carotenoid levels (Stimpson and Lackan, 2007). Even the empty nest can alter food habits for older couples. Older adults may stop cooking after children leave home, or increased intake may result because of an inability to decrease amounts of food prepared. Elder adults who are cared for by an adult son or daughter may have their usual intake altered with fewer choices available. Loss of mobility to shop for food occurs when physical impairments make driving a car or using public transportation difficult. Isolation from others will result unless there are friends or family members on whom the elder person can rely. Entering a nursing home profoundly changes eating habits. It is human nature not to deal well with change. Any change in the social environment can trigger depression, which can lead to overeating or undereating with concomitant changes in weight and nutritional status.

Alcohol plays a role in many adult lives. In college, binge drinking is common. One study found almost one quarter of college student current drinkers reported mixing alcohol with energy drinks. The combination of caffeine in the energy drinks with the alcohol can further impair judgment (O’Brien and colleagues, 2008). Older adults lose their ability to metabolize alcohol as efficiently as when they were younger, leading to alcohol-related problems such as falls.

Caffeine plays a central role in most adults’ lives. The older adult is most likely to drink black coffee or tea, whereas young to middle-age adults have designer coffees or caffeinated soft drinks and the younger adults may eat coffee beans or consume energy drinks that are marketed to this population. Most are not drinking the caffeinated beverages intentionally as a fluid source, although they do contribute fluid for bodily needs. A study of consumers of energy drinks found two thirds drank one container due to lack of sleep or energy provided, whereas about half drank three or more with alcohol while partying. About one out of five consumers of energy drinks reported they caused headaches and heart palpitations (Malinauskas and colleagues, 2007).

ECONOMIC CHANGES

A young adult, often earning minimum wage, may find it difficult to purchase nutritious foods. Learning how to budget to include the essentials is an important step in maintaining health throughout life. With advancing age, retirement from work usually results in a decrease in income at a time when an increased amount of money is being spent on medical care. As a result, less money may be available for food. High-protein foods may be consumed in lesser amounts because they are expensive and require preparation and many are difficult to chew and swallow. Young and old alike may consume excessive amounts of high-carbohydrate foods, which are inexpensive, easily stored without refrigeration, and simple to prepare.

PHYSICAL CHANGES

Once the growth spurt of adolescence is past, the need for kcalories decreases. During the aging process the basal metabolic rate begins to slow during the early adult years. By the middle adult years the amount of lean body mass (muscle tissue) begins to reduce. Exercise needs to be part of daily activities and will help to maintain muscle strength and tone throughout the adult years. Even bedridden older adults can exercise (Figure 13-4).

FIGURE 13-4 Exercise is possible even for bedridden adults.

During the later years, perceptual changes may affect eating behavior. Taste may be altered because of a decrease in the number of taste buds that occurs either as part of the aging process or as an effect of disease states, nutritional deficiencies, or medications. A reduced ability to detect odors and impaired hearing and sight may reduce the enjoyment of the social aspects of eating. All these perceptual changes may contribute to reduced food consumption. Reduced senses also increase the risk of food poisoning for the older adult who has impaired vision, taste, and smell (see Chapter 14 for guidelines on food safety).

Loss of teeth, found even with young adults and prevalent in the elder population, may lead to altered food choices that decrease the nutritive value of the diet. Ill-fitting dentures will also affect food choices. If refined foodstuffs are eaten instead of raw fruits and vegetables, alterations in gastrointestinal function may lead to constipation, especially at older ages, because of a decrease in the body’s ability to move waste products through the gastrointestinal tract. Increasing the fiber content of the diet and maintaining an adequate fluid intake and exercise are important for gastrointestinal functioning.

With decline in function of organs such as the liver and kidneys, the metabolism and excretion of food nutrients are altered. Use of protein is altered with liver disease, and buildup of toxins can occur when the kidneys lose their ability to filter harmful substances. These health declines may be apparent with younger adults who have had chronic illness since childhood.

Because the sense of thirst diminishes with older adults, it is especially important for such individuals to be aware of the need for fluids to prevent dehydration. This is particularly true for a person taking diuretics to promote loss of excess fluid. However, for an individual with advanced renal disease or ascites (fluid buildup in the abdomen) from liver digease, fluid restrictions may be imposed.

Decreases in body secretions also occur with the older adult. For example, swallowing may become more difficult because of decreased saliva production, and protein digestion is less efficient because of decreased hydrochloric acid secretion. The body’s production of digestive enzymes decreases with aging as well. Table 13-1 summarizes the effect of the physiologic changes in the older adult.

Table 13-1

Physiologic Changes in the Older Adult

COMPONENT	FUNCTIONAL CHANGE	OUTCOME
Body composition	↓ Muscle mass	↑ Fat tissue in muscle size and strength
	↓ Basal metabolic rate	↓ Caloric requirements
	↓ Bone density	↑ Risk of osteoporosis
Perceptions	↓ Hearing	Feeling of isolation
	Slowing of adaptation to darkness	Reluctance to eat in public places or at large social affairs
		Need for brighter light to perform tasks
	↓ Number of taste buds	↓ Ability to taste salt, sweet
		↑ Ability to taste bitter and sour
Gastrointestinal tract	↓ Smell	↑ Threshold for odors
	↓ Motility	Constipation
	↓ Hydrochloric acid	↓ Efficiency of protein digestion
		More prone to food poisoning
	↓ Saliva production	Difficulty swallowing
Heart	↑ Blood pressure	↓ Ability to handle physical work and stress
Lungs	↓ Ability to use oxygen	↑ Fatigue
	↓ Capacity to oxygenate blood	↓ Capacity for exercise
Endocrine	↓ Number of secretory cells	↓ Blood hormone levels
	↓ Insulin production	↑ Blood glucose level
Kidney	↓ Renal blood flow	↓ Capacity for filtration and absorption

Even though little is known about an elder person’s nutritional needs, meals should be planned according to the five-food-group system of the MyPyramid Food Guidance System, as discussed in Chapter 1. Six small meals per day are often more appropriate than three full-size meals for someone with a small appetite.

Teaching Pearl

The elder population was raised to respect authority figures. Consequently, many will adhere to advice given by health care providers, even if the advice is not in their best interest. Thorough assessment of nutritional habits, including fluid intake and other factors influencing eating habits and health requirements, needs to be conducted before any nutritional guidance is given, in order to avoid unintentional harm to the elder population. Manners and showing respect, including appropriate attire, are very important to many of the elder population and include being addressed as Mr., Mrs., or Miss, unless the individual states otherwise. Middle-age and younger adults generally prefer being called by their first name.

WHAT ARE THE NUTRIENT NEEDS OVER THE LIFE SPAN?

ENERGY

Younger adults typically require 2000 to 2500 kcal daily. For this reason, the Daily Values found on food labels list the amounts of fat, carbohydrate, and protein based on these levels (see Figure 1-4). There is, however, a wide range in caloric needs for individuals, based on body composition, level of physical activity, age, and metabolism. For any adult, generally a minimum of 1200 to 1500 kcal is required to have an adequate nutritional intake, and most young adults will lose weight at these levels. For athletic adults the minimum kcalorie needs are generally at least 2000 kcal.

We know that energy needs are lower for the older adult because basal metabolism decreases gradually with aging owing to a decrease in lean body tissue. Older adults generally have the same minimum needs for micronutrients and protein as younger adults, with the minimum number of servings of the MyPyramid being necessary throughout the adult life span.

PROTEIN

Protein requirements do not decrease with age. It is now generally believed that a slightly higher need for protein exists for the elder population at 1.0 g/kg of body weight—versus 0.8 g/kg for the younger adult—because of the diminishing efficiency of protein use in the older adult. Athletic adults need a higher protein intake of up to 1.5 g/kg of body weight to a maximum of 2.0 g/kg of body weight. Factors such as renal health and serum albumin levels help determine individual protein needs. Also, for people of any age, protein requirements increase in response to certain types of physiologic stress, such as infection, bone fractures, surgery, and burns. The minimum number of servings of the MyPyramid easily meets the basic protein needs of most adults. Exceptions exist mainly for pregnant women, athletes, and those who have more immediate needs, such as for healing from trauma.

With aging there is loss in both muscle mass and strength. This is called sarcopenia. There is some evidence that protein intake, especially from animal sources, may help reduce the risk of sarcopenia (Lord and colleagues, 2007). Milk, with its high protein content, has been found to promote increased muscle mass, especially along with resistance exercise (Wilkinson and colleagues, 2007).

VITAMINS AND MINERALS

The Dietary Reference Intakes (DRIs) for vitamins and minerals are similar in older and younger adults. Eating a healthy, well-balanced diet continues its importance throughout the life span. Women living in the community who have higher serum selenium and carotenoid levels are at a lower risk of death (Ray and colleagues, 2006). On the other hand, low serum micronutrient (carotenoids, vitamins E and D) levels have been shown to increase the risk for frailty in older women. The more micronutrient deficiencies, the greater the risk of frailty (Semba and colleagues, 2006). Maintaining adequate intake of foods high in folate is important throughout the life span for its role in cell division and protein metabolism. Folate is important to help prevent cardiovascular disease in individuals who have hyperhomocysteinemia (see Chapter 7).

Taking a multivitamin and mineral supplement may be helpful for the older adult who has nutrient deficiencies. However, there can be problems with excess nutrients from multivitamins such as if the person has renal insufficiency, in which a buildup of vitamin A can occur, and especially if fortified foods also are consumed in large amounts such as with fortified cereals that may be eaten more than just at breakfast. Iron is another micronutrient that can be consumed in excess with supplements. Although the need continues to be high for the young adult woman due to losses incurred from menstruation and pregnancy, this is not the case with the older adult. The DRI of iron for women over 50 years old matches men’s need. This is the approximate time of menopause for most women. This is reflected in the lower amounts of iron found in multivitamin and mineral supplements designed for the older adult, such as Centrum Silver or men’s preparations. An increased need for iron, however, may develop after surgery, as a result of blood loss. Worsening iron deficiency anemia in an older adult may be a result of gastrointestinal blood loss from a medical condition, and the cause of the anemia needs to be determined.

Maintaining appropriate intake of calcium and vitamin D from the diet alone can be a challenge for a variety of reasons such as allergies or dislike of milk. Generally 1200 mg calcium and 400 International Units of vitamin D (1 mcg of vitamin D equals 40 International Units) is required daily for most adults (see differences as noted in the DRIs at the back of the book). For persons who can drink 1 quart (4 cups) of vitamin D–fortified milk, this will provide the recommended 1200 mg of calcium and 400 International Units of vitamin D. Equivalent amounts of cheese and yogurt will provide calcium but are generally low in vitamin D. As previously reviewed, a higher intake of vitamin D may be advisable in areas with limited sunshine such as in Northern areas of the world. Adults with limited sunshine, such as those who remain indoors, are advised to take increased amounts of vitamin D. A supplement of 800 International Units of vitamin D per day in combination with calcium has been shown to reduce the risk of falls and fractures (Mosekilde, 2005). Others have recommended up to 1000 International Units of vitamin D in the elder years, in conjunction with a healthy diet that provides a variety of vitamins and minerals for optimal bone health (Nieves, 2005). Total calcium and vitamin intake needs to be considered by health care professionals before supplementation is advised. Serum vitamin D levels (25[OH]D—see Chapter 3) can be monitored. The nutrient needs of the elder population over 80 years of age are not as well known. The DRI guidelines currently provide only for greater than 70 years (see the back of the book). Identification of possible unique needs of the elder population will be determined through further research.

Cultural Considerations

The older generation who lived on farms would have had liver at slaughtering times. It appears that the message, beginning in the 1970s, to reduce cholesterol intake resulted in many adults who not only don’t eat eggs, but also don’t eat liver. Although liver is high in cholesterol, it is low in total fat and saturated fat and is extremely high in a number of micronutrients (see Tables 3-1, 3-2, 3-3, and 3-4). Encouraging the reintroduction of liver into the diet of an older adult can greatly round out the nutritional quality of his or her diet.

HYDRATION

Adequate fluid intake is important throughout life. Adults generally require an intake of 1 mL/kcal or 30 to 35 mL/kg of body weight. This generally equates to at least 2 L or 8 cups of total fluids daily for most adults. Adults involved in athletics may have special needs (see section below). Any adult who has excess loss of sweat from work or leisure activities will need increased amounts of fluids. Fluid needs will increase for lactating women. Excess fluid intake can also occur but is usually not dangerous unless fluid is being pushed beyond the thirst mechanism.

For older adults or those involved in strenuous sports the sense of thirst is not an adequate indicator of fluid need. In athletic sports, rapid loss of fluid from sweat may occur that needs to be replenished before the recognition of thirst is apparent. With age, the sense of thirst diminishes. Dehydration in the older adult is associated with increased risk for falls because dehydration adversely affects the sense of balance. Other health issues with chronic dehydration include dental decay and impaired swallowing because of reduced saliva flow, very low blood pressure, and increased risk for urinary tract infections (UTIs). Signs of dehydration include fatigue, mental confusion, poor skin tone, loss of ability to sweat, and constipation.

Adults who take diuretics are at increased risk for dehydration. Excess alcohol intake, without intake of other sources of liquids, may cause dehydration because alcohol is a diuretic. With renal impairment, the ability to concentrate urine becomes impaired and increases the risk of dehydration. Adults with heart failure or edema may need to follow fluid restriction, generally about 25 mL/kg of body weight.

Teaching Pearl

A graphic description of the color of normal urine can help adults recognize hydration. Urine that is dark yellow or amber generally reflects dehydration. An adult who is trying too aggressively to increase fluid intake may note clear urine. Normal urine color is pale yellow. Comparing amount of fluid intake to the color of urine excreted can help to recognize a need for greater or lesser intake. The message that anything that melts or is a liquid is considered a fluid source may be helpful (with the exception of alcohol and fats). Caffeinated beverages are not as able to be used as a fluid source because of their weak diuretic effect but do contribute to hydration status.

FIBER

Fiber is also important throughout life. It serves as a marker at any age for intake of a variety of trace minerals. Minerals are essential for the numerous metabolic activities that occur within the body cells.

In older adults, low fiber intake is related to chronic disorders such as diverticulosis and constipation. The recommended amount is about 25 g/day, which is reflected in the U.S. Department of Agriculture (USDA) MyPyramid minimum number of servings of fruits, vegetables, and whole grains. It is particularly easy to meet the fiber and mineral goals through the consumption of legumes, which on average contain three to four times the fiber content of any other plant-based food.

When providing advice on increasing fiber intake, it also is important to emphasize fluids. A high fiber intake with insufficient fluids can lead to bowel impaction. This is particularly important for the older population, who may not recognize when they are becoming dehydrated. Inadequate hydration status should be suspected whenever reduced bowel function or constipation develop.

Teaching Pearl

The correlation of fiber and mineral content of food can be related through the description of plant growth. Minerals are microscopic rocks (refer back to Chapter 3) that are drawn from the soil by the roots of various plants (whole grains, vegetables, fruits, and so on). The minerals are tied up with the fiber in plant-based foods.

WHAT ARE SOME NUTRITION ISSUES FOR WOMEN?

PREMENSTRUAL SYNDROME

Premenstrual syndrome (PMS) occurs the first few days before the onset of the monthly menstrual cycle and disappears after menstruation. A high intake of calcium (1300 mg) and vitamin D (700 International Units) may reduce the risk of PMS (Bertone-Johnson and colleagues, 2005).

The majority of American women experience some degree of PMS with increased appetite, anxiety, irritability, and headaches. Although these symptoms are similar to ones indicating hypoglycemia, eating does not always relieve these symptoms as would be expected in treating hypoglycemia. Nutrition has no known affect on PMS. Eating small, frequent meals may help with control of hunger without resulting in weight gain of adipose tissue. Including dairy foods and a variety of whole grains, legumes, and nuts can help provide the minerals as discussed previously.

Premenstrual dysphoric disorder (PMDD) is the more severe and disabling form of PMS. This condition is estimated to occur in 2% to 9% of menstruating women. The selective serotonin reuptake inhibitor (SSRI) antidepressants, used either continuously or only during the luteal phase, lead to rapid improvement in symptoms and functioning (Freeman and Sondheimer, 2003).

MENSTRUAL MIGRAINES

Migraine incidence is similar between the sexes before puberty and after age 50 with the onset of menopause. About one out of four women of reproductive age experience migraines, three times the incidence of males (Raña-Martínez, 2008). Pregnancy allows for temporary cessation of menstrual migraines. Menstrual migraine attacks are more severe, of longer duration (potentially lasting more than 3 days), and are typically difficult to treat (Pringsheim, Davenport, and Dodick, 2008). Triptan medications, in particular sumatriptan, are the most effective in the management of acute menstrual migraine attack (Allais and Benedetto, 2004). See section below for dietary factors in the prevention of migraine.

Although the pathogenesis of menstrual-related pain conditions is not fully understood, menstrual-related overproduction of prostaglandins is implicated in the pathophysiology of both menstrual migraine and dysmenorrhea (Mannix, 2008).

MENOPAUSE

Menopause is the permanent cessation of ovarian activity. Women have symptoms of menopause for a number of years before complete onset. This period is referred to as perimenopause, or the time around menopause. These symptoms can consist of weight gain, mood swings, increased serum cholesterol levels, and hot flashes. The physical changes associated with hot flashes consist of increased peripheral blood flow with a feeling of heat that is not registered as body temperature, increased heart rate, and profuse sweating. It is believed this is a disturbance of the temperature-regulating mechanism found in the hypothalamus. Asian women have lower incidence of hot flashes, which has been thought to be due to higher intake of soy products and their natural phytoestrogen content. However, dietary supplementation with phytoestrogens has not provided the same effect as hormone replacement therapy (Sturdee, 2008). Consuming soy products, rather than supplements, may be of benefit.

Questions of safety and efficacy continue with herbal products. Black cohosh has been reported to be useful in the treatment of menopausal symptoms; however, the research on this herb is limited. Adverse events such as nausea, vomiting, headaches, dizziness, breast pain, and weight gain have been observed in clinical trials. A few cases of hepatotoxicity have been reported, but a direct link has not been made with black cohosh. Black cohosh does not appear to act like estrogen, a concern for women at risk for estrogen-dependent breast cancer (Mahady, 2005). Because there are few studies on the impact of herbs for control of hot flashes, and the supplement industry is largely unregulated, herbs cannot yet be widely recommended. Because women may seek their own alternatives, health professionals need to be aware of possible side effects from over-the-counter herbal products.

WHAT ARE NUTRITIONAL NEEDS FOR PHYSICAL ENDURANCE, STRENGTH, AND HEALTH IN SPORTS AND PHYSICALLY DEMANDING OCCUPATIONS?

SPORTS NUTRITION ISSUES

Increasingly, adults of all ages are engaging in sports (see Figure 13-1). There are a variety of reasons from simple pleasure to body building or health reasons. There are many positive reasons to maintain a high level of physical activity throughout the adult life span.

In regard to decreasing insulin resistance to help manage diabetes, it has been observed that high-intensity exercise is more effective than moderate intensity. With the equivalent of 1000 kcal per week of high-intensity exercise, insulin sensitivity and metabolism of glucose increased 20% (Coker and colleagues, 2006). Aerobic and resistance exercise have been found to be comparable in improving glucose metabolism in older men (Ferrara and colleagues, 2006).

In helping to maintain muscle mass in older ages, a higher level of physical activity also is needed. Leisure type activities were found to be insufficient in preventing sarcopenia in persons greater than 65 years of age (Raguso and colleagues, 2006). Minimizing inflammatory conditions among older adults also appears necessary to minimize loss of muscle strength (Schaap and colleagues, 2006). Adequate protein intake is further important, with some evidence that older adults require a higher intake of protein beyond the DRI of 0.8 g/kg of body weight to maintain muscle mass. Goals for protein need to be evaluated in terms of preexisting renal or liver disease that precludes an increased intake.

The foundation of a nutritious diet with appropriate amounts of kcalories, protein, and fluids is essential for all adults. Individual needs are dictated by body size, age, and type of sports in which one is involved.

An elite athletic adult who is involved with endurance sports will have different needs than an adult who is focusing primarily on increasing muscle strength or is engaged in leisure activities. Although many athletes choose to take performance-enhancing supplements, sound nutritional status is still fundamental for peak performance.

For the health professional working with athletes, understanding the fundamental nutritional needs and interventions is essential. Being able to help prevent and correctly identify the cause of exercise-induced problems is paramount in preventing physical injury or mortality of athletes. Resistance training is not without potential harm. It is associated with periods of acute intracellular hypoxia (lack of oxygen within the body cells ) and low intramuscular pH levels. Rhabdomyolysis (a condition resulting from muscle injury with release of cell contents into the plasma) can be caused by overly aggressive resistance training such as excessive weight lifting. Excess physical tension on the muscle fibers and lowered levels of adenosine triphosphate (ATP) with altered electrolyte levels in the cell can induce this condition. Symptoms of rhabdomyolysis include muscle soreness, reduction in the range of motion, decreased muscle strength, black urine, and, in severe cases, acute renal failure. A gradual training program with maintenance of appropriate hydration is advised to prevent this condition (Heled and colleagues, 2005).

Being able to distinguish the relatively benign exercise-associated hypotensive collapse caused by events such as marathon runs or triathlons from potentially fatal conditions is essential for proper treatment. Hyponatremia (low serum sodium levels less than 135 mEq/L), dehydration, hyperthermia, and diabetes-related hypoglycemia are all potentially lethal conditions that require different nutritional interventions.

PROTEIN NEEDS

Most adults easily meet their protein requirements. With adequate kcalorie intake, protein needs are only slightly increased for low- to moderate-intensity endurance at an estimated 1.0 g of protein per kilogram of body weight. Results suggest that a protein intake of 1.2 g/kg or 10% of total energy intake is needed to achieve a positive nitrogen balance for higher levels of physical activity. This is not a concern for most endurance athletes who routinely consume protein at or above this level (Gaine and colleagues, 2006). For the elite athlete the maximum protein requirement has been estimated at 1.6 g/kg of body weight (Tarnopolsky, 2004).

Diet plays a role in promotion of muscle mass with adequate kcalories and protein required. Protein requirements for novice weightlifters are not elevated (Moore and colleagues, 2007). This is due to the beneficial effect of resistance training that lowers requirements for protein initially (Hartman, Moore, and Phillips, 2006). Ultimately, increased dietary protein intake (up to 1.6 g of protein per kilogram of body weight daily) may best promote increased muscle development in response to resistance exercise. Adequate protein and kcalories is particularly important for the elder population in this quest (Evans, 2004). Including milk after resistance exercise has been shown to improve the body’s uptake of amino acids needed in muscle protein production. Evidence suggests whole milk may be more efficient at protein synthesis than low-fat milk (Elliot and colleagues, 2006). The benefit of milk may be more important in groups of persons with low levels of lean mass and strength such as the elderly (Phillips, Hartman, and Wilkinson, 2005). Healthy young men who routinely include milk after exercise were shown to have greater muscle growth during early stages of resistance training when compared with soy or carbohydrate sources (Hartman and colleagues, 2007). The optimal amount of the milk proteins, casein and whey, has been observed at 40 g/day of whey protein plus 8 g/day of casein for the greatest increase in lean tissue development (Kerksick and colleagues, 2006). Young adults generally do not need supplemental protein sources beyond that provided by diet to increase lean tissue mass and strength (Candow and colleagues, 2006).