Dietary consequences of oral health in frail elders
This chapter focuses on the etiology and consequences of undernutrition and nutritional deficiencies in frail elders, and the interrelationship of this with oral health. An overview of how nutritional needs change with advancing age is presented. This is followed by a discussion of evidence for a relationship between loss of teeth, prosthodontics, quality of life, and nutritional well-being, including how nutritional status is assessed in geriatric populations. Finally, we offer practical suggestions for appropriate foods for older people who are frail and have oral health-related eating problems.
THE IMPORTANCE OF GOOD NUTRITION FOR FRAIL ELDERS
Nutrition and diet are key factors in healthy aging. Undernutrition and micronutrient deficiencies are common among older people, but they are not inevitable consequences of being old. Indeed, prevention of dietary inadequacy helps promote good general and oral health, and promotion of good oral health can impact on dietary adequacy and nutritional well-being.
NUTRITIONAL NEEDS OF OLDER PEOPLE
A healthy and balanced diet low in saturated fat and free sugars but high in fruits, vegetables, wholegrain foods, and fiber plays a key role in preventing a number of chronic diseases, including dental caries, diabetes, cardiovascular disease, and some cancers (World Health Organization, 2003). Continuing a healthy balanced diet maintains this protection into old age. Elders who consume 5–10 portions of fruits and vegetables daily when compared with elders who consume less can reduce by one-third their risk of atherosclerotic disease (Liu et al., 2000). In addition, a healthy balanced diet will also help prevent constipation, optimize immune function, and maintain a healthy body weight. Constipation is a chronic problem for many older adults due to reduced peristaltic strength, which is often coupled with an inadequate intake of dietary fiber. Obesity is a risk factor for disability, and a sedentary lifestyle is a risk factor for obesity. Together they contribute to a vicious cycle. Indeed, obesity is associated with functional decline even among community-dwelling elders who are relatively active and healthy (Jensen and Friedman, 2002). The immune response declines with age, and intake of nutrients has an important role in optimizing the function of the immune system in later life.
Energy requirements in old age
Energy requirements decrease due to loss of lean body mass and, in some, a more sedentary lifestyle as we get old (Fujita and Volpi, 2004). They are reduced by approximately 10%–16% in people aged 75 years and over (Institute of Medicine of the National Academies, 2005). To put this into context, the average daily energy requirement of a typically active 70-kg man aged 39–59 years is around 10.5 megajoules (MJ), whereas for a man of similar weight aged 75 years or over it is 8.8 MJ (Department of Health, 1991). Energy intakes, despite this, often fail to meet energy requirements (McDowell et al., 1994; Liu et al., 2000). The U.K. National Diet and Nutrition Survey (NDNS) of people aged 65 years and over indicated that about 1 in 20 (4% of men; 6% of women) aged 75–84 years living in the community were underweight, but the prevalence rose to as high as 1 in 5 older men living in residential care (Finch et al., 1998). Data from the United States suggest that approximately half of long-term care residents are malnourished (Neel, 2001), and 6 out of 10 older people in acute care hospitals in the United Kingdom are at risk of malnutrition (Age Concern, 2006).
Importance of dietary protein in old age
A diet adequate in protein is important to minimize loss of lean body tissue that tends to occur after age 70 years. Protein energy malnutrition (PEM) in older people is associated with reduced lean body tissue, reduced bone mass, impaired cognitive function, poor wound healing, reduced immune response, and increased morbidity and mortality (MacIntosh et al., 2000). Weight loss in later life is often disproportionately due to a loss of lean muscle tissue rather than adipose tissue. This loss of lean body tissue will impact body strength and mobility and, if marked, increases the risk of falls (Gariballa and Sinclair, 2005). Protein requirements in adults are approximately 1 g/kg body weight/day (Department of Health, 1991), but it has been suggested that the level of intake of protein should be increased to ∼1.25 g/kg/day for elders (Fujita and Volpi, 2004).
Changes in requirements for micronutrients in old age
Despite a lower requirement for energy, the requirement for many vitamins and minerals does not decrease with age, and can increase due to reduced absorptive capacity of later life. This means that a diet that is nutrient dense is advocated.
Adequate intake of iron is important for prevention of anemia in later life (Eisenstaedt et al., 2006), for optimum immune function (Ahluwalia, 2004), and for wound healing. Absorptive capacity for iron is often reduced in later life. Vitamin C promotes iron absorption; therefore, concurrent consumption of foods containing iron and vitamin C should be encouraged to maximize the absorption of dietary iron. However, concurrent consumption of tea should be discouraged since it can bind with iron in the gut, reducing absorption further.
Calcium is required to maintain bone mass and lower the risk of osteoporosis. However, dietary intakes by elders often fall short of requirements. It has been suggested that an intake of 1,500 mg/day may be required, but usually dietary intakes fail to reach 1,000 mg/day (Finch et al., 1998).
Zinc has a role in many enzymes and proteins, and it impacts on gene expression and on immune function. Moderate zinc deficiency is often observed in old age (Blumberg, 1997) probably due to marginal intake coupled with reduced absorptive capacity. The U.S. National Health and Nutrition Examination Survey showed that more than half (57%) of the U.S. population over 70 years had less than adequate intake of zinc (Briefel et al., 2000). Several factors may interfere with its absorption, such as a high intake of phytates or grains. Malabsorption, physiological stress, and trauma reduce zinc status, which dampens the immune response, disturbs taste perception (Meunier et al., 2005), impairs wound healing (Haase et al., 2006), reduces appetite (Little et al., 1989), and can contribute to age-related osteoporosis (Heaney, 1986). Low concentration of serum zinc is also associated with reduced cognitive function in old age (Ortega et al., 1997).
Vitamin D has an important role in maintaining bone mineralization, and an adequate intake is required to minimize age-related reduction in bone density (Thomas, 2001) and thereby to prevent osteoporosis (Schneider, 2008). Younger people get most of their requirements entirely by the action of the sun on the skin; however, elders need to consume about 10 µg/day (found in approximately five sardines!) because of the reduced ability of the kidneys to hydroxylate vitamin D to its active form.
Elders, especially if frail and housebound, are also at increased risk of vitamin D deficiency because the precursor to the vitamin in the skin decreases with age, and older people frequently lack exposure to the synthesizing effect of sunlight on vitamin D through the skin (Thomas, 2001). It is difficult to maintain adequate serum vitamin D levels through diet alone (Dawson-Hughes, 2008); therefore, supplements of vitamin D and calcium might help prevent fractures of older bones (Schneider, 2008).
Vitamins B12 and folate
Adequate vitamin B status, particularly folate and B12, might be important in preventing dementia (Brachet et al., 2004). Consumption of foods rich in vitamin B12 tends to be reduced in old age (Wakimoto and Block, 2001). Animal protein foods provide the richest sources, but they can be expensive and difficult to chew (Chernoff, 2005). Digestion of vitamin B12 requires that it be released from protein complexes in the gut; however, age-related achlorhydria and other gastrointestinal disorders reduce the ability to disassociate these complexes (Hurwitz et al., 1997). B12 helps the nervous system to function; therefore, there are hopes that dietary supplements of B12 might delay the onset of dementia (Bourre, 2006).
Folate is an important vitamin for older people and subclinical deficiency has been associated with depression and cognitive decline, including Alzheimer’s disease and other forms of dementia (D’Anci and Rosenberg 2004). It might protect against cognitive decline in older people (McNulty and Scott, 2008). Folate and vitamin B12 are needed for transmethylation of neuroactive substances, and this process may be altered if the vitamins are deficient, causing depression and/or dementia—the so-called “hypomethylation hypothesis” (Wolters et al., 2004). A low folate status is associated with increased levels of homocysteine, which contributes to vascular disease, dementia, and Alzheimer’s disease.
It is not yet certain that cognitive impairment can be reduced by nutritional intervention to lower homocysteine levels, but the possibility is being investigated. An insufficiency of folate may occur in older people due to low intake, reduced absorptive capacity, or consumption of medications that alter folate status. Therefore, adequate dietary intake of folate is important for frail elders.
Synthesis of collagen requires vitamin C, which has an important role in wound healing and vascular integrity. It is a powerful antioxidant that protects against age-related oxidative damage. Adequate vitamin C status is also required for optimal immune function.
Achieving a diet that is nutrient-dense with adequate micronutrients can be difficult at any age, but even more so for frail elders due to eating difficulties.
Older adults living in residential and nursing care homes
Malnutrition is common in older people living in residential care facilities, and it contributes to morbidity and mortality, but typically, it impacts negatively on general well-being and quality of life (Crogan and Shultz, 2000; Neel, 2001). There is little information available on the prevalence of malnutrition among frail elders living in residential care. A survey of nutritional status on admission to a care home in the United Kingdom, for example, found malnutrition in approximately one in three residents: Prevalence was higher if they had transferred from an acute-care hospital and other care homes, whereas malnutrition was less prevalent (about one in four) if the residents came directly from their own homes (Russell and Elia, 2008). Similar information has surfaced from Belgium, France, and Spain (Lamy et al., 1999; Dion et al., 2007; Gil-Montoya et al., 2008), with as many as half of the residents of care homes at risk of malnutrition. In the United States, between 50% and 85% of the residential care population is malnourished (Crogan et al., 2001; Neel, 2001).
Causes of malnutrition in older people
A complexity of problems including social, financial, and functional barriers to achieving adequate food intake contributes to malnutrition in older people. Illness, reduced appetite and/or disease-related anorexia, depression, loss of mental capacity, loss of ability to shop and cook, along with chewing and swallowing problems all contribute to the development of malnutrition (Moynihan, 2007).
Socioeconomic factors and disease have a greater impact than advancing age on nutritional status (Gariballa and Sinclair, 2005). Anorexia is common in old age due to age-related early satiety (MacIntosh et al., 2000), diminished taste and sensory perceptions (Mioche et al., 2004), and use of medications that depress appetite and sometimes taste sensation (Morley, 1997). Older people consume smaller meals and eat more slowly, with few snacks between meals (Morley, 1997). Therefore, oral health is just one of many factors impacting on how older people choose and eat food.
Diagnosis of nutritional deficiencies in all older adults is difficult, and symptoms are often unseen until there are clinical signs of advanced nutritional deficiency (Gariballa and Sinclair, 2005). Early signs of micronutrient deficiencies are often seen initially in the mouth, and therefore, the dentist has an important role in early diagnosis of deficiencies (Mioche et al., 2004).
There are numerous instruments available for assessing the presence and severity of undernutrition in frail elders, but not all have been adequately validated (Green and Watson, 2005, 2006). The Malnutrition Universal Screening Tool (MUST) established by the British Association for Parenteral and Enteral Nutrition is the preferred instrument for nutritional screening for older persons in the United Kingdom (Elia, 2003), while the Mini Nutritional Assessment (MNA®) developed by Nestlé Nutrition in the 1990s is popular in North America (Bauer et al., 2008). Both measures are used for assessing and screening older populations (Green and Watson, 2005, 2006).
DOES MASTICATORY ABILITY PLAY A ROLE IN ACHIEVING GOOD NUTRITION AMONG FRAIL ELDERS?
Association between dentition and nutrition
The number of natural teeth and their position as opposing pairs are related to chewing ability, and people without teeth or even with dentures tend to chew less effectively compared with people with healthy natural teeth. A reduced ability to chew possibly impacts on selection of food and intake of nutrients, which puts older people at risk of malnutrition. The evidence for a causal relationship between chewing ability and dietary intake is, however, equivocal.
Both masticatory ability and nutrition can be assessed using a variety of measures. Masticatory ability can been assessed using dentition as a proxy measure of chewing ability, clinical measures, and subjective perceptions of chewing ability and oral health-related quality of life (OHRQoL). Nutrition is assessed using dietary assessment methods (food and/or nutrient intakes); anthropometric measurements of height and weight from which body mass index (BMI) is calculated; nutritional screening/assessment tools, such as the MNA; and biological markers such as serum albumin. Variations in the definition of “dentate” and grouping study participants by the status of their dentitions, along with varying methods of assessing nutritional status and inadequacies in reporting these dietary studies, makes it difficult to compare results and limit the conclusions that can be drawn. Moreover, the vast majority of research studies in this area have a cross-sectional design, which seriously restricts inferences or conclusions about whether tooth loss changes diet.
There are two possible scenarios associated with a compromised dentition and nutritional status. Eating difficulties may reduce food intake because it is uncomfortable to chew, leading to a lower energy intake, greater risk of malnutrition, and a lower BMI. Alternatively, they may lead to selection of softer processed foods that may be less nutrient dense but higher in energy, leading to a greater risk of malnutrition and a higher BMI.
Complete denture-wearers can experience difficulties eating some foods, particularly foods that are hard, sticky, or with seeds, such as steak, apples, raw carrots, tomatoes, fresh bread, and toffees (Ettinger, 1973; Sheiham and Steele, 2001). Hard foods might also be avoided by people with few natural teeth, particularly older people who are frail (Sheiham and Steele, 2001). People with ≥20 natural teeth, when compared with denture-wearers, do eat more fruits and vegetables, although the difference is relatively small (Johansson et al., 1994; Joshipura et al., 1996; Sahyoun et al., 2003; Hung et al., 2005; Ervin and Dye, 2009). It is unclear yet whether a higher or lower energy intake is associated with dental status; however, edentulous people have lower intakes of nutrients associated with fruits and vegetables, that is, dietary fiber, vitamin C, carotenes, and folate, although again these differences are small (Joshipura et al., 1996; Krall et al., 1998; Sheiham et al., 2001; Marshall et al., 2002; Hung et al., 2005; Ervin and Dye, 2009).
BMI may be used as an indicator of malnutrition, with a BMI <18.5 defined as underweight and BMI ≥25.0 as overweight (World Health Organization, 2006). In the absence of illness, a low BMI suggests that energy intake does not meet energy expenditure, whereas a high BMI suggests that energy intake exceeds energy expenditure. The relationship between the status of a dentition and BMI is complex, but the pattern emerging is that a higher BMI is associated with a compromised dentition. In other words, people who are edentate and who wear one or no denture, and people without a functionally natural dentition or with many missing natural teeth without a denture, are more likely to be overweight or obese (Sheiham et al., 2001; Rauen et al., 2006; Mack et al., 2008; Hilgert et al., 2009). The pattern might be different with frailer elders living in an institution where residents with a dysfunctional dentition have a significantly lower BMI than elders with better function (Mojon et al., 1999). The likelihood of malnutrition, as defined by the MNA, is higher in those with fewer teeth or no dental prosthesis (Lamy et al., 1999; Dion et al., 2007; De Marchi et al., 2008). Plasma albumin has been used widely as a biochemical indicator of nutritional status to assess the risk associated with dentition (Lamy et al., 1999; Musacchio et al., 2007; Sadamori et al., 2008). However, it is too insensitive and nonspecific to make a good indicator of nutritional status (Crook, 2009).
Diet and masticatory ability
We have seen that the dentition is associated with diet and with risk of malnutrition in frail elders, but are these differences due to a decreased chewing ability, or is a compromised dentition a marker for other factors associated with an inadequate intake of nutrients?
Masticatory ability has little impact on intakes of fruits and vegetables, energy and nutrients, or risk of malnutrition in older adults (Krall et al., 1998; Lamy et al., 1999; Marshall et al., 2002; Shinkai et al., 2001, 2002; Bartali et al., 2003; Chen and Huang, 2003; Liedberg et al., 2007; Bradbury et al., 2008; Gil-Montoya et al., 2008). Factors such as attitude to healthier eating, increasing age, difficulties swallowing, cognitive decline, death of a spouse, living in an institution, in addition to physical limitations associated with age, such as difficulty carrying a shopping bag, are equally or even more important than compromised masticatory ability (Bartali et al., 2003; Chen and Huang, 2003; Dion et al., 2007; Musacchio et al., 2007; Bradbury et al., 2008; Gil-Montoya et al., 2008).
EFFECT OF PROSTHODONTICS ON DIET AND NUTRITIONAL STATUS
There is reasonable evidence of an association between the dentition and nutrition. However, the association between chewing difficulties and compensatory alterations to diet is weak and inconclusive, probably because frailty in old age is itself associated usually with few teeth, chewing difficulties, and malnutrition. Consequently, it is almost impossible to separate the affect of one association from the others.
Loss of teeth and a poor diet have many risk factors in common, such as low socioeconomic status, poor education, and tobacco smoking. The unhealthy diets of those with relatively few teeth, rather than being a consequence of tooth loss, probably contributed to the loss of teeth. Eating habits and diet in childhood and adolescence typically continue into old age, so that children who eat healthy diets are likely to eat healthy diets as adults (Maynard et al., 2005; Mikkilä et al., 2005; Newby et al., 2006).
Impact of prosthodontics on dietary intake
Masticatory efficiency is improved dramatically by implant-supported dentures (van Kampen et al., 2004). However, improved masticatory efficiency does not necessarily lead to improvements i/>