status, dehydration, and healthy ageing
Older adults are at risk for dehydration because of both reduced fluid intake and increased fluid losses. Ageing is associated with a reduction in thirst in response to water deprivation that is observed in a lower self‐reported thirst score during dehydration and in ingestion of less water after the dehydration period. Acute weight loss of ≥3% of total body mass or more than 1 kg weight loss per day points to the possibility of dehydration. It is a common and potentially lethal problem in both institutionalized and community‐dwelling elderly people. In hospitals, the mortality rate may be up to 50% in older adults with dehydration. The most common causes of dehydration are infection, altered level of consciousness, cognitive impairment, and use of diuretics. Schols et al.13 concluded that dehydration is a common problem in nursing homes, often due to failures in the detection of dehydration and appropriate management. An overload of water and salt is also common and may result in impaired recovery from surgery or perioperative mortality and morbidity. The general recommendation for elders is to consume approximately 1.5 l of fluid daily.
Bone loss, nutrition, and healthy ageing
Bone loss commences around age 40 and then averages between 0.5 and 1% per year in men. Women have accelerated bone loss around menopause ranging from about 2% per year. Bone mineral density (BMD) loss of 2.5 SD below the mean for younger adults is considered osteoporosis by WHO criteria.14 Osteoporosis is a multifactorial disease characterized as ‘a systemic skeletal disease characterized by low bone mass and microarchitectural deterioration of bone tissue, with a consequent increase in bone fragility and susceptibility to fractures’. Both environmental and genetic factors play an important role in the risk, prevention, and progression of osteoporosis. The prevalence of osteoporosis varies widely by geographic and enthno‐racial strata. For instance, the NHANES III study15 showed that low BMD is most common among elderly non‐Hispanic white women (21% osteoporosis) and Mexican American women (20% osteoporosis) and lower in non‐Hispanic black women (18%). In Europe, it is estimated that 179,000 men and 611,000 women suffer a hip fracture every year, and these numbers are expected to double in the next 40 years.16,17
Although a low percentage of variance in the bone mass is attributable to nutritional factors (<20%), it can still have a significant impact. The benefits of supplementing populations at risk for osteoporosis with vitamin D and calcium are well established in studies with endpoints such as effects on BMD, bone turnover, and a reduced risk of fractures without side effects. The vitamin D requirement may be higher in regions where calcium intake is low. Vitamin D also has a beneficial effect on the risk of falling, explained by improved muscle function. Evidence for associations between optimal protein intake and bone mass is diverse, with positive, negative, and no associations all having been found. Other dietary factors such as vitamin K, vitamin A, caffeine, fluoride, phosphorus, strontium, and zinc are also under investigation and hotly debated for promotion of bone health.18
Energy intake, macronutrients, and satiety in ageing
Population‐based nutritional surveys have shown a gradual decline in energy intake in old age. Shifts in the proportion of energy coming from various macronutrients with ageing is unclear. Between populations, the macronutrient composition appears to vary considerably. Across studies, intakes range from 12 to 18% protein, 20 to 42% fat, and 38 to 65% carbohydrate.19
Prentice20 considered the extent to which the development of recommendations for dietary energy needs to account for the sources of energy (i.e. macronutrient profiles). He discussed the issue with a view to avoiding undernutrition in addition to obesity. He concluded that ‘at the metabolic level, only diets with the most extreme macronutrient composition would have any consequences by exceeding the natural ability to modify fuel selection. However, diets of different macronutrient composition and energy density can have profound implications for innate appetite regulation and hence energy consumption’. The Omni‐Heart study,21 a randomized three‐period cross‐over feeding trial, studied self‐reported appetite and selected fasting hormone levels by comparing the effects of three diets, each with a different macronutrient profile. It was concluded that a diet rich in protein from lean meat and abundant in vegetables reduces self‐reported appetite when compared with diets high in carbohydrate and unsaturated fats. Satiety was not explained by hormonal changes, leaving putative mechanisms unclear.
The role of proteins in the diet is currently being extensively studied and discussed, not only because of the satiating effect. Alterations in the ability of cells to regulate homeostasis underlie the pathogenesis of severe human diseases. Even in the absence of disease, deterioration of protein homeostasis likely contributes to different aspects of ‘normal ageing’. This makes it difficult to formulate evidence‐based requirements for proteins in the diet of (frail) elderly people. There is a general consensus to moderately increase protein intake above 0.8 g /kg−1 body weight in the elderly (up to 1.5 g /kg−1), which may help to reduce progressive muscle loss and stimulate muscle protein anabolism. Current gaps in our understanding of altered protein homeostasis in ageing urgently require further studies.22
Determinants of dietary preference and intake among older adults
It is generally recognized that food preference is affected by a variety of factors, including biological (i.e. hunger, sense of taste and smell), economic (i.e. cost, socioeconomic status), structural (i.e. access, education, cooking facilities, skills, and time), social (i.e. culture, family, peers, and meal patterns) and attitudes, beliefs, and knowledge about food. Ageing is associated with a decline in the ability to smell (olfaction) and taste (gustatory) (Figure 12.1). It is estimated that over half of those between ages 65 and 80, and more than 75% of those over 80, have a measurable decline in olfactory sense.23 The decline in sense of smell lowers quality of life by impairing the sense of flavour in food and beverages and the identification of hazards such as spoiled foods. Deems et al.24 reported that 46% of older adults with olfactory dysfunction have a change in appetite or body weight. Olfactory dysfunction has more recently been reported as an early risk factor for neurodegenerative diseases.25
Figure 12.1 Decline in olfaction with age. University of Pennsylvania Smell Identification Test (UPSIT) scores as a function of subject age and gender. Numerical data points indicate the sample size for each age group. Note that women identify odorants better than men of all ages.
Source: Doty et al.23 ©1984, The American Association for the Advancement of Science.
Social isolation, loneliness, institutionalization, and lower socioeconomic status in older adults is associated with consuming an unbalanced diet.26 Locher et al.27 found that ethnicity and gender were risk factors for dietary intake disturbances. Older black women were most at risk followed by older black men and older white women. They concluded that what contribute most to nutritional deficiencies are social isolation, low income level, limited support and social capital, including transportation to food shops and congregated meal sites, and also limited independent life span.
Institutionalized elders also tend to have a lower energy intake, mainly due to lower fat and protein intake. Furthermore, nutrient inadequacy is more prevalent in the institutionalized elderly than in community‐dwelling groups. At the same time, no clear differences in food patterns have been observed. Therefore, the main cause of the higher prevalence of nutrient inadequacy in dependent elders may be the low level of total caloric intake. An exception might be the group with a poor state of dentition. In both the NHANES III and SENECA studies, lower diet quality was observed due to avoidance of food groups such as meat, fruit, and vegetables in people with dental issues – a finding consistent