Changes in Nutritional Needs With Aging
Teresa Juarez-Cedillo1,2, 1Mexican Institute of Social Security, Mexico City, Mexico, 2National Autonomous University of Mexico, Mexico City, Mexico
Abstract
Knowing the causes of changing nutritional needs and dietary preferences is needed before we can understand the health status of elderly populations. Nutritional deficiencies have been associated with increases in morbidity and mortality, so consuming a balanced and nutritious diet is important for the elderly. However, normal aging is associated with changes in body composition and nutritional requirements. As healthy people age, body fat increases, muscle mass and total body water decrease, and the number of calories necessary to maintain body weight declines. These changes are influenced by life events, illnesses, genetic traits, and socioeconomic factors. For this reason, diet and nutrition play important roles in maintaining health and preventing disease. This article describes some aspects of normal aging and their effects on nutritional status, and it introduces some of the screening tools used to identify an older adult’s nutritional risks. In addition, basic interventions for commonly encountered problems in the office setting are discussed.
Keywords
Nutrition; elderly; dietary supplements; nutrient needs; weight loss
Introduction
Aging brings physiological, physical, mental, social, and environmental changes that can negatively impact the nutritional status of the elderly population regardless of medical conditions or lifestyles. Knowing the causes of changing nutritional needs and dietary preferences is needed to understand a patient’s nutritional status. To meet their nutritional needs, more than just diet must be considered. Although there is no uniformly accepted definition of malnutrition in the elderly, common indicators include involuntary weight loss, abnormal body mass index (BMI) (Leonard and Ulijaszek, 2002), specific vitamin deficiencies, and decreased dietary intake (Reuben et al., 2004). Even though older persons are particularly vulnerable to malnutrition, attempts to provide them with adequate nutrition often encounter practical problems. First, nutritional requirements for the aging are not well defined. Since both lean body mass and basal metabolic rate decline with age, an older person’s energy requirement per kilogram of body weight is also reduced. Understanding that diet and nutrition play an important role in maintaining health, preventing disease, and functioning (WHO, 2003), this chapter reviews the changing nutritional needs of aging, diagnostic evaluation, and management of elderly patients and offers guidelines for the prevention of disabilities related to nutritional needs.
Age-Related Changes Affect Nutrition
As people age, multiple changes affect an individual’s nutritional status. The main body composition changes are a loss of fat free mass and fat mass from muscles, organ tissues, skin, and bone (Hebuterne et al., 2001). This change in the body composition leads to a decrease in basal metabolic rate, which translates into a lower requirement for other nutrients (Olson et al., 1989). Hence, an approximate doubling of body fat between ages 20 and 50 has been observed (Perissinotto et al., 2002; Roberts and Dallal, 1998). Some authors have determined that fat increases at a rate >7.5% per decade in both genders (Hughes et al., 2002) and that older subjects have a mean of fat tissue 7 kg higher than younger ones (Piers et al., 1998). The basal metabolism or energy requirements for the elderly diminish by about 100 kcal/day per decade. For some seniors, it may be difficult to meet daily micronutrient requirements with this reduced caloric intake (Morley, 1997; Compher et al., 1998).
Age-related changes to the gastrointestinal tract may affect oral intake, but it is unclear if these normal physiological changes themselves contribute to decreased food intake (Westenhoefer, 2005). Oral and dental issues, esophageal motility, and atrophic gastritis may also affect nutritional status. The latter may be implicated in impaired vitamin B12 and iron adsorption (Wells and Dumbrell, 2006).
In addition to gastrointestinal physiological changes, renal function declines with age. This decreases responsiveness to antidiuretic hormones, which often results in an increased risk of dehydration in older patients and may also affect vitamin D adsorption (Compher et al., 1998).
It is well known that aging is associated with a gradual decline in energy requirements, a reduction in the basal metabolic rate, and a physiological diminution in food intake (Zafon, 2007). Recent studies has revealed the existence of genes involved with hormonal signals that play an important role in the regulator of energy metabolism, including fat storage (Cheng et al., 2004). Hence, genetic approaches provide a direct demonstration that aging is related to a metabolic reorganization of adipose tissue. The aforementioned ideas are consistent with the concept that aging is associated with a shift away from energy use toward energy storage. Other points to consider are the changes related to diseases common in older persons.
Changes in Nutritional Needs
Many older adults face changes that can affect their food intake and nutritional status. Many need fewer calories to maintain their weight but still need the same amounts of vitamins and minerals as they did when they were younger (DH, 1991; Roberts and Dallal, 2005).
Consuming a diet that meets nutrition requirements without exceeding energy requirements poses an additional challenge for older adults and requires limiting discretionary energy intake. Recent evidence on dietary trends is concerning. The usual intake for a large percentage of older adults ages 51–70 was below the minimum recommended amounts, especially for nutrient-rich food groups. More than 90% of persons 51–70 years old and >80% of persons 71 and older had intakes of empty energy that exceeded the discretionary energy allowances (Krebs-Smith et al., 2010).
The dietary fiber intake of older adults is lower than recommended levels (Food and Nutrition and Institute of Medicine, 2005). In addition to providing nutrients such as vitamins, minerals, and antioxidants, fiber provides benefits such as improved gastric motility, improved glycemic control, and reduced cholesterol. About 60% of calories should come from carbohydrates, with emphasis on complex carbohydrates. Vegetables, fruits, grain products, cereals, seeds, legumes, and nuts are all sources of dietary fiber. Foods low in fiber are frequently inferior in nutrient composition and contribute to discretionary energy intake, thereby decreasing the nutrient density of the diet and placing older adults at risk of malnutrition and obesity. For this reason, is very important that when making recommendations regarding the fiber content in the diet of an older adult, fluid intake must be appropriately assessed and guidelines for adequate fluid should accompany those for dietary fiber (Food and Nutrition and Institute of Medicine, 2005).
Water is the most important of all nutrients and serves many essential functions. Adequate water intake reduces stress on kidney function, which tends to decline with age. Adequate fluid intake also eases constipation. With the aging process, the ability to detect thirst declines, so it is not advised to wait to drink water until one is thirsty. The kidneys’ decreased ability to concentrate urine, blunted thirst sensation, endocrine changes in functional status, alterations in mental status and cognitive abilities, adverse effects of medications, and mobility disorders are commonly reported risk factors for dehydration in older adults. Individuals should be sure to drink plenty of water, juice, milk, and coffee or tea to stay properly hydrated. The equivalent to eight glasses of fluid should be consumed every day (Amella, 2007). Dehydration, a form of malnutrition, is a major problem in older adults, especially persons aged 85 and older and institutionalized older adults (Food and Nutrition and Institute of Medicine, 2005). Regular consumption of high-quality proteins can be challenging for older adults with physical and environmental limitations (Chernoff, 2004). The question of whether or not dietary protein needs change with advancing age is subject to scientific debate. Studies suggest that 0.8 g of dietary protein per kilogram of body weight daily is adequate to meet minimum dietary needs. Although a protein intake moderately greater than that amount may be beneficial to enhance muscle protein anabolism and reduce progressive loss of muscle mass with age. Some experts suggest that a protein intake of 1.0 g to 1.6 g/kg daily is safe and adequate to meet the needs of healthy older adults. Aging does not impair the ability to synthesize muscle protein after consumption of foods rich in high-quality protein or a high-quality protein meal and resistance exercise. Therefore, some experts now recommend that older adults consume between 25 and 30 g high-quality protein at each meal. For many older adults, this primarily means including a high-quality protein source at each meal throughout the day as recommended in the US Department of Agriculture’s MyPlate food guidance system (Tholking et al., 2011; Bernstein et al., 2012).
Using Supplements
Although little research has been conducted on micronutrient requirements in the elderly, certain key nutrients demand attention (Rand et al., 2003). Among the micronutrients, the significant ones associated with deficiencies in the elderly include vitamins A, B12, C, and D and calcium, iron, zinc, and other trace minerals.
Vitamin B12 is a nutrient of interest in the old primarily because the consumption of foods rich in this nutrient decreases with age (Wakimoto and Block, 2001). An estimated 6–15% of older adults have a vitamin B12 deficiency, and approximately 20% are estimated to have marginal status. The atrophic gastritis is a severe impediment to the transport and release of vitamin B12. The production of gastric acid is necessary to digest food rich in vitamin B12 such as animal protein. The vitamin B12 requirements that are not met through diet can be met with supplements that contain crystalline vitamin B12, although there is still a limited bioavailability (Olson et al., 1989). For elderly adults, the recommendation to meet vitamin B12 needs is through foods fortified with B12 or that naturally contain B12. The primary source of vitamin B12, is expensive, difficult to chew, and has been associated with elevated blood lipids. Further research is needed to investigate the efficacy and benefits of fortification of foods with vitamin B12 in older adults (Green, 2009).
It has been suggested that dietary vitamin A be obtained from an increased intake of carotenoids, including β-carotene among others. Compromised hepatic function may contribute to an increased risk of toxicity, particularly in those who are using supplements or eating fortified foods. Vitamin A has many roles in the maintenance of health; it is important to maintain normal vision, for cell differentiation, efficient immune function, and genetic expression. Vitamin A recommendations for older adults have been lowered from previous editions of the recommended daily amounts. Current suggested levels are 700 μg retinol activity equivalents (RAEs) for women and 900 μg RAE for men. Some researchers have recommended that these recommendations be set at even lower levels because, although the vitamin A intake for many older adults is below current recommendations, their vitamin A levels remain normal (Bjelakovic et al., 2014).
Vitamin D and Calcium
Among their numerous benefits, adequate vitamin D and calcium are best known for their crucial role in the prevention and delay of the progression of osteoporosis. Older adults are at high risk of vitamin D inadequacy because of limited sources of vitamin D in the diet (fortified milk, fatty fishes), less exposure to sunlight, a decreased capacity to synthesize vitamin D in the skin even when exposure to sunlight is plentiful, and a decreased capacity of the kidneys to convert vitamin D into its active form (Nieves, 2003). There are two primary sources of vitamin D: diet and skin. Dietary sources of vitamin D are fatty fishes and fortified dairy products. Skin as a source for vitamin D precursor may be helpful for those who live in temperate climates, but for those who live in warmer areas fear of skin cancer is an impediment to activating vitamin D precursors. In addition, the vitamin D precursor found in skin decreases with age. Adequate intake of calcium and vitamin D are difficult to achieve from food alone. Historically, calcium and vitamin D from dietary or supplement sources have been the major therapeutic focus for bone health. The ability of the kidney and liver to hydroxylate vitamin D precursors is affected by age, thereby suggesting that the vitamin D requirements might be higher than have been recommended (Shiue, 2016). Other nutrients such as protein, vitamins A and K, magnesium, and phytoestrogens are also involved in bone health, and research continues to expand the understanding of the roles of these nutrients in the bone health of older adults (Kitchin and Morgan, 2003; Nieves, 2003).
Iron is a mineral naturally present in many foods and added to some food products and available as a dietary supplement. Iron is an essential component of hemoglobin, an erythrocyte protein that transfers oxygen from the lungs to the tissues (Wessling-Resnick, 2014). As a component of myoglobin, a protein that provides oxygen to muscles, iron supports metabolism (Aggett, 2012). Iron is also necessary for the growth, development, normal cellular functioning, and synthesis of some hormones and connective tissue (Aggett, 2012; Murray-Kolbe et al., 2010).
Dietary iron has two main forms: heme and nonheme (Wessling-Resnick, 2014). Plants and iron-fortified foods contain nonheme iron only, whereas meat, seafood, and poultry contain both heme and nonheme iron (Aggett, 2012). Heme iron, which is formed when iron combines with protoporphyrin IX, contributes about 10–15% of total iron intake in Western populations (Aggett, 2012; Food and Nutrition and Institute of Medicine, 2005).
Most of the 3–4 g of elemental iron in adults is in hemoglobin (Aggett, 2012). Much of the remaining iron is stored in the form of ferritin or hemosiderin (a degradation product of ferritin) in the liver, spleen, and bone marrow or is located in myoglobin in muscle tissue (Wessling-Resnick, 2014). Humans typically lose only small amounts of iron in urine, feces, the gastrointestinal tract, and skin (Drakesmith and Prentice, 2012). Needs for iron in older males revert to the same levels as those for adult males: 10 mg/day (Garry et al., 2000; Fleming et al., 2002).
Zinc has been recognized as an essential mineral with a role in many enzymes, gene expression, and immune function, among other physiological functions. Marginal intake of dietary zinc will lead to lower physiologic zinc levels, but the real challenge may be factors that inhibit or interfere with zinc absorption. Consequences of poor zinc status may include reduced immune function, dermatitis, loss of taste acuity, and impaired wound healing. Zinc supplementation may contribute to a reversal of symptoms in individuals who are zinc deficient. In individuals who have adequate zinc status, however, supplementation will not improve their conditions (Beckett and Ball, 2015).
Copper is a trace mineral that is part of several enzymes and proteins that are essential for the body to adequately use iron. Lower copper intake has been implicated with other variables such as heightened cholesterol and in some studies as a possible risk factor for cardiovascular disease. Due to the difficulty in measuring copper status, the many factors such as zinc, carbohydrate, and vitamin C intake that affect copper bioavailability remain unknown (Wu et al., 2002). Copper is widely distributed in a variety of foods and is relatively accessible if a diet with variety is consumed in adequate amounts. Estimated average requirements for copper for adults to age 70 have been established at 700 µg/day (Arredondo and Núñez, 2005).
There is little specific information regarding micronutrient requirements for elderly. It seems that the metabolic changes that occur with aging would have some impact on vitamin, mineral, but there is a clear need for future research to elucidate these nutrient needs.
Assessing Nutritional Status
A comprehensive assessment of nutritional status includes anthropometric measurements, laboratory values, physical exam, and patient history. Anthropometric measures include height, weight, BMI, body fat measurement, and muscle mass measurement. Laboratory values should include albumin, retinal-binding prealbumin, transferring, complete blood count, serum folate, vitamin B12, and cholesterol. A diet history is helpful if there is good 24-h recall or if a food record for 3 days leading up to the exam can be completed.
The elderly are vulnerable to a number of nutritional risks because of associated multiple pathologies and the frequent changes in body composition and nutritional needs they undergo. Furthermore, nutritional assessment in the elderly is especially difficult because many of the signs of malnutrition are also associated with aging. Recently, rapid-application scales have appeared for the purpose of allowing nutritional assessment in geriatrics; these instruments can be classified according to their objective and scope of application.
Nutritional Screening Initiative, Level I and II Screening
This set of instruments is well suited to community screening. It incorporates a simple nomogram to determine BMI and a questionnaire of laboratory data (albumin and serum cholesterol), clinical characteristics, eating habits, living environment, and mental and cognitive states. Level II adds skinfold measurements and biochemical indicators. The objective of these instruments is to estimate the magnitude and causes of malnutrition (Montorio and Lázaro, 1996). The questionnaire, applied separately, can be used as an indicator of high, medium, or low risk of malnutrition.
Mini Nutritional Assessment
This questionnaire was created for the elderly population and can be applied in cases of ambulatory or hospitalized care. It qualifies the condition of a malnourished patient, the risk of malnutrition, and the general nutritional status. It can be performed in approximately 10 min with a total possible score of 30 points. A score above 23.5 classifies the individual as well fed; scores between 17 and 23.5 indicate a situation of risk, in spite of no evidence of loss or biochemical alteration; and scores below 17 express a situation of malnutrition (Guigoz et al., 1996).
Mini Nutritional Assessment–Short Form
This abbreviated form was created to reduce the time of administration to 10 min without losing diagnostic power and thus simplifying and generalizing implementation in clinical practice. Among its characteristics, the following stand out: good correlation with the mini nutritional assessment (MNA), adequate sensitivity and specificity, and good internal consistence. This form presents false positives when compared with customary dietary assessment due to the fact that it detects not only malnourished individuals but also those at risk of malnutrition. This version consists of six questions that can be effectively asked in approximately 3 min. The questionnaire should be used in two phases: (1) filling out the short form and if a risk of malnutrition is detected (score lower than or equal to 11 points), then (2) the entire questionnaire is administered (Rubenstein et al., 2001).
Malnutrition Universal Screening Tool
Initially, this tool was developed for noninstitutionalized individuals, but currently its use has been validated in various contexts, including the hospital environment, external consultation, and home residences (Stratton et al., 2004). Its limitations include not incorporating any measure of functionality and a focus on acute disease.
Subjective Global Assessment
This method was designed by Detsky et al. (1987) to estimate nutritional status through clinical history and physical exploration. It has greater sensitivity and specificity than assessment with measurements of albumin, transferrin, cutaneous sensitivity, anthropometry, height creatinine, and the prognostic nutritional index. The subjective global assessment (SGA) can be used to determine which patients require nutritional intervention and which would benefit from intensive nutritional support.
The data obtained from the clinical history include the evolution of weight, current dietary intake in relation to customary dietary intake, digestive symptoms present in the preceding 2 weeks, functional capacity, and metabolic requirements. Within the scope of the physical examination are evaluations of loss of subcutaneous fat and musculature and the presence of edema or ascites. Each element is evaluated as light, moderate, or severe, and patients are classified into three groups: adequate nutritional status, suspicion of malnutrition or moderate malnutrition, and severe malnutrition.
Laboratory tests based on blood and urine can be important indicators of nutritional status, but they are influenced by nonnutritional factors as well. Lab results can be altered by medications, hydration status, and disease states.
Clinical data provide information about an individual’s medical history, including acute and chronic illness and diagnostic procedures, therapies, or treatments that may increase nutrient needs or induce malabsorption (Older Americans Act, 2016).
Conclusion
There is little specific information regarding micronutrient requirements for the elderly. One challenge in defining nutritional needs is the heterogeneity of elderly adults. To understand the dietary needs of the older adult, it is important to know what the basic requirements of the healthy older adult are and whether the metabolic changes that occur with aging will have some impact on a vitamin or mineral. For this reason, there is a clear need for future research to elucidate these nutrient needs. A comprehensive assessment must include a lot more than just basic nutritional assessment and should consider the person’s overall physical, mental, and psychosocial status. This will lead to a better understanding of how to realistically meet the nutritional needs of older adults compounded by the likelihood of multiple chronic conditions, the use of many prescriptions, and the variable quality of nutritional intake associated with limited income, disability, and institutionalization.