Nutritional challenges for the elderly.

KEY POINTS

* There are an increasing number of elderly people with a wide range of body weights, chronic diseases, disabilities and food preferences.

* The elderly are the largest group of nutritionally vulnerable people in Australia, with those in residential care establishments having the greatest nutritional risk.

* Unintentional weight loss is associated with increased morbidity and mortality. It is not clear whether weight reduction in older obese adults has beneficial health and quality-of-life outcomes. Weight loss achieved through adoption of a healthy diet plan combined with increased physical activity could be of benefit.

* There is a reduction in energy requirements with increasing age, whereas there are increased requirements for a number of nutrients, such as: protein, riboflavin, vitamin B6, calcium, vitamin D and, for some, vitamin B12. Therefore, it is difficult for older people on relatively low-energy diets to meet their nutrient requirements from food, and vitamin supplements and/or fortified foods may be required to meet nutrient requirements.

* To ensure optimal nutritional status, we must assess nutritional requirements on an individual level and provide practical advice regarding appropriate food choices which takes into account, physical and psychological conditions, body weight, level of physical activity, medication use, food preferences, income, ethnic group, social support, access to retail food outlets, cooking facilities and access to community support schemes.

* There is a reduction in appetite with increasing age; therefore, one of the key challenges is keeping older people interested in food through the development of meals and snacks that are both nutritious and appetising.

* Animal sources of protein are generally well accepted by older people, and if tender cuts of meat are chosen and cooked correctly, even small amounts can assist the elderly to maintain adequate intakes of protein, vitamin B12 and iron

INTRODUCTION

Australia is going grey at an amazing rate. For the first time in Australian history (by 2021), those over the age of 65 years will outnumber those under 15 years. By 2051, nearly 25% of the population will be over 65 years and 5% will be over 85 years. (1) Although preventative health strategies commencing in early life are likely to have the greatest effect on chronic disease, significant reductions in morbidity and mortality can also be achieved through the adoption of healthy dietary practices in later life (between 70 and 90 years). (2) Importantly, these lifestyle improvements are likely to allow us to maintain a good quality of life in our later years. The new Nutrient Reference Values (NRVs) for Australia and New Zealand (3) have taken this into account because, for the first time, they have incorporated recommendations to reduce chronic disease risk. The suggested dietary targets for 'optimising diets' include recommendations for: vitamins A, C and E, selenium, folate, sodium/potassium, protein, fat, carbohydrate, dietary fibre, linoleic acid, [alpha]-linolenic acid, and omega-3 long-chain fats (docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA)). These recommendations are relevant not only to younger adults, but also to the older age groups.

The body composition of older people varies widely, with an increasing number of obese persons surviving into old age, but this is also coupled with an increasing number of underweight older people in those over the age of 80 years. (4) The ageing process results in a reduction in skeletal muscle mass and body weight. (5,6) Height, body weight and body mass index (BMI) decreases after age 70 years. (5) Increasing frailty (characterised by exhaustion, low walking speed and low hand grip strength) is seen in those over 70 years of age, resulting in reduced quality of life. (7) Low body weight is associated with poor physical function, disability (8) and a decline in muscle strength, (9) and it is well established that being underweight is associated with increased mortality. (10-12) Loss of body weight is associated with increased risk of hip fracture, (13-15) reduced mobility (16,17) and increased mortality. (18,19) Underweight older people are at increased risk of consuming inadequate amounts of nutrients due to low energy intakes. The ability to meet dietary requirements for older people may be further compromised by drug-nutrient interactions or by the presence of chronic diseases, which affect absorption, transportation, metabolism and excretion of essential nutrients. The majority of elderly people suffer from a range of chronic diseases, at different levels of severity, and most take some type of medication, with many taking a large number of different drugs daily. These chronic diseases can also be combined with, and/or result in, reduced appetite, (20) difficulties in self-feeding, poor mobility, (21) dementia (22) and depression. (23) Those in residential care establishments are particularly at risk. One recent Australian study found that, on one day, more than half of the residents were at risk of consuming an inadequate energy intake, although wastage was not excessive and energy served was adequate. (24) Common medical conditions associated with ageing, environmental issues relating to access of food, cooking facilities, social isolation and low income can further exacerbate nutritional problems. The presence of these numerous risk factors signifies that the elderly are the most nutritionally vulnerable group in Australia today.

Malnutrition in the elderly is difficult to diagnose, as there is no one optimal single measurement and there is an acknowledgement that malnutrition is a continuum. (25) However, most definitions of undernutrition do include an anthropometric measure (weight for height or BMI) with or without weight loss. (26) There are few large-scale studies on the nutritional status, using anthropometric measures, of free-living elderly people, but limited data from overseas indicate that the prevalence of low body weight ranges from 5% in the USA (BMI <18.5 kg/[m.sup.2]), (27) to 15% in Europe (BMI <20 kg/[m.sup.2]). (28) In the elderly residential care setting, the prevalence of low body weight is higher than in the community-dwelling elderly. Pauly et al. (29) conducted an analysis of all published reports of malnutrition in nursing home residents and found large variations in prevalence. Eight studies reported that 10-50% of residents had a BMI <20 kg/[m.sup.2]. Weight loss was reported in seven studies, with prevalence rates between 5% and 41%, and reduced serum albumin (indictor of protein status) (<35 g/L) was reported in 10 studies, with prevalence rates between 0% and 50%. (29)

In addition to these anthropometric measurements and physical characteristics, a range of biochemical markers have been used to assess malnutrition. Many of the readily available serum markers, however, provide little information on the body stores of specific nutrients. In Australia there are limited published data, but recently an Australian study found in a sample of 115 elderly residents in a residential care facility, low serum 25-hydroxy-vitamin D (25(OH)D) concentrations among 79% of residents, and 46% had low serum zinc (<10.7 [micro]mol/L). Only 7% of residents had no deficiencies or insufficiencies (based on body weight, serum 25(OH)D, albumin, folate, vitamin B12 and zinc). (30) On the other hand, the obesity epidemic now has reached the elderly with an increasing number of overweight and obese people living to an older age. In older groups particularly, obesity has also been associated with poor physical performance, (31) functional limitations (32) and disability. (33) Overweight and obese people may also be at nutritional risk due to the continued consumption of higher-energy/low-nutrient-density foods, and fail to meet their nutrient needs even though they may not be consuming particularly low-energy diets.

It is unclear whether being obese is also associated with increased mortality in this age group. (34,35) However, evidence from a recent intervention study (36) suggests that intentional weight loss, achieved through a balanced diet, when combined with increased physical activity, is beneficial to health. This contrasts to the situation of unintentional weight loss in later life, which is detrimental to health. (16) With these issues in mind, this paper considers the nutritional requirements of elderly Australians and the potential contribution of red meat to meet nutritional challenges for this group.

NUTRITIONAL REQUIREMENTS FOR ELDERLY AUSTRALIANS

The new NRVs, for the first time, make provision for the changing nutrient requirements with age, and the NRVs now include different recommendations for adults, 18-50 years, 51-70 years and greater than 70 years. (3) These new NRVs reflect the increasing body of evidence that older people actually have increased dietary requirements for a range of nutrients, including: protein, riboflavin, vitamins B6, calcium and vitamin D (Table 1). Additionally, vitamin B12 is not as well as absorbed in the elderly, particularly in those with atopic gastritis, although this is not reflected in the Australian NRVs. However, older people also have reduced energy requirements due to reduction in basal metabolic rate (BMR), which is related to reduced muscle mass.

Protein

Protein-energy malnutrition (PEM) is associated with impaired muscle function, decreased bone mass, immune dysfunction, anaemia, reduced cognitive function, poor wound healing and delayed recovery from surgery, and ultimately increases morbidity and mortality. (37) It is more difficult for older people to maintain nitrogen balance and, consequently, the new NRV for protein is greater in older people. Compared with younger people, those over the age of 70 years have an approximate 20% higher daily requirement for protein. Evidence from an intervention study suggests that an increase in dietary protein intake can result in enhanced muscle hypertrophy in the elderly when combined with high-intensity resistance exercise training. (38) So it may be possible to reduce some of the age-related loss of muscle, but it does not appear possible to completely prevent this muscle loss.

Protein is an important component of bone, and higher protein intakes have been associated with reduced risk for hip fracture (39,40) and greater bone density. (41,42) Recent studies suggest that higher protein intakes would be beneficial for the elderly, particularly in light of adverse health consequences attributable to PEM. In a prospective study, women with protein intakes ranging from 1.20 to 1.76 g/kg body weight, tended to have fewer health problems over a 10-year period than those with protein intakes <0.8 g/kg body weight. (43)

The source of protein in the diet is also of importance. Where diets are restricted in variety and size, as is often the case in the elderly, choosing protein foods with a high biological value, such as meat, milk and eggs, can be important to ensure that essential amino acid requirements are met.

Calcium

Older people experience a 0.5-1% reduction in bone mass per year that commences in the 4th-5th decade of life. In women there is an additional accelerated loss in bone mass of 1-2% per year for up to 10 years around the age of menopause. (44) This reduction in bone density contributes to the high rates of hip and vertebral fracture seen in older people. (45) This reduction in the bone mass can be attenuated in old age by consuming an adequate intake of calcium and maintaining a reasonable level of physical activity, particularly weight-bearing activities.

Zinc

There appears to be a reduction in the effectiveness of the immune system with increasing age, leading to an increased incidence of infections and an extended time to recovery. (46) There is a role for zinc (Zn) in elderly people, particularly in behavioural and mental function, immunity and bone metabolism. (47) However, there are few randomised controlled trials demonstrating health benefits. There is evidence from the 1995 National Nutrition Survey that zinc intakes are low in older people, particularly women, where 43% of women had an intake of zinc less than 70% of the 1991 Recommended Dietary Intake. (48)

B vitamins and iron

The process of ageing has a significant effect on gastrointestinal function, with a decrease in the secretion of gastric acid, intrinsic factor and pepsin, which can reduce the bioavailability of vitamin B6, vitamin B12, folate, iron and calcium. The iron requirement of older people is relatively low, but factors associated with old age may increase the risk of iron-deficiency anaemia. The UK National Diet and Nutrition Survey in people over the age of 65 years found that 34% of men aged >75 years and 21% of women aged >75 years had a low haematocrit. (49) Approximately 94% of the total iron intake in this population was in the form of non-haem iron. Cereal products provided almost half the iron intake of the participants in this survey, but cereal products did not correlate with iron status, possibly because of the low bioavailability of iron from cereal products. (50) Dietary intakes of alcohol, vitamin C, protein, haem and non-haem iron and fibre were positively associated with iron status. Consumption of meat, poultry and fish was positively associated with six measures of iron status, and the authors concluded that a varied diet containing meat, poultry and fish, vegetables and fruit, with a moderate intake of alcohol makes a positive contribution to the iron status of elderly people. (49)

Common diseases associated with old age lead to poor absorption and, combined with use of medications, increase the risk of iron-deficiency anaemia. Older people who are not vegetarians should be encouraged to consume foods containing bioavailable haem iron, such as red meat, liver and meat products, to maintain adequate iron status. (51) Haem iron is only minimally affected by other components of a meal, such as phytic acid and calcium. Non-haem iron can, however, be greatly affected by such components. (49) This may be of particular significance for the elderly (particularly those in nursing homes) who drink a lot of tea and may consume milk products with meals.

THE ROLE OF MEAT IN THE DIET FOR THE ELDERLY

In Australia the median intake of combined meat, poultry and game products and dishes, estimated from the 1995 National Nutrition Survey, in older people (>65 years) was 127 g/day for men and 83 g/day for women. There also appears to be a reduction in meat intake with increasing age, as these amounts represented a 34% lower intake than that consumed by those aged 25-44 years. (52) There also appears to be a tendency for the elderly to reduce their consumption of red meat over time. A longitudinal study of non-institutionalised people aged 70 years in New Zealand found, over a six-year period, a significant decrease in the number of meat servings per month for both men and women. (53) In a cross-sectional study (26) of 1368 free-living and institutionalised older people in the UK, subjects defined as being at high risk of undernutrition were more likely to eat less meat and meat products (119 g vs 141g/day) and protein (57 g vs 63 g/day).

Meat is a major contributor of protein, niacin equivalents, iron, zinc and vitamin B12 in the Australian diet. (54) Red meat provides many important nutrients, particularly protein, omega-3 long-chain fatty acids, iron, zinc, selenium, vitamins B12 and B6, and possibly vitamin D. In addition to preventing nutrient deficiencies in older people, meat is also a good source of nutrients that are associated with the reduction of chronic disease. Vitamins B6 and B12 can reduce circulating homocysteine levels, a recognised risk factor for cardiovascular disease, (55) although it is not clear whether reducing homocysteine levels results in a beneficial effect on health. Additionally, polyunsaturated and monounsaturated fats, B vitamins, especially vitamins B6 and B12, appear to be protective against cognitive decline in the elderly. (56) Although red meat is viewed as a contributor to saturated fat intake, lean red meat contains a higher proportion of unsaturated fatty acids, together with the omega-3 long-chain fatty acids, EPA, DPA and DHA, (57) which could contribute to reduction in cardiovascular disease (58) as well as improved cognition.

It has been suggested that meat may be a useful dietary source of bioavailable vitamin D for those who do not receive sufficient exposure to sunlight to synthesise vitamin D, (59) but more research is need to assess the content and role of meat in maintaining vitamin D status in older people in Australia. The rates of vitamin D deficiency are highest in the elderly, housebound and in residential care, ranging from 45% to 75%. (60,61) Some older people may have reduced their consumption of red meat as they find it difficult to chew; however, recipes that include appropriate tender cuts of red meat, combined with the correct cooking methods, do result in dishes that many older people find appetising.

SUMMARY

Nutritional health is an integral component of overall health, independence and quality of life in old age. (62) In addition, a diet which is nutritionally inadequate can contribute to, or exacerbate, chronic and acute disease, hasten the development of degenerative diseases, and delay recovery from illness. (63) Individual assessment of older people is fundamental to ensuring adequate nutrition. It is not possible to treat the older population as one group, as food and nutritional needs vary widely. Assessment of nutritional requirements, taking into account individual requirements, and practical advice regarding appropriate food choices is required. Factors for consideration include: income, ethnic group, food preference, social support, access to retail food outlets, cooking facilities, access to community support schemes (e.g. Meals on Wheels), level of disability (both mental and physical), also body weight, body composition, presence of chronic disease and medication use. Older people should be encouraged to eat a range of easily digestible foods that they enjoy with a high level of micronutrients. The use of fortified foods can assist older people to meet their micronutrient needs; however, the diets of older people must contain sufficient amounts of macronutrients, particularly protein. Animal sources of protein are generally well accepted by older people, and if tender cuts of meat are chosen and cooked correctly, even small amounts can assist the elderly to maintain adequate intakes of protein, vitamin B12 and iron. It is a challenge for many older people to maintain their interest in food, as there is a reduction in appetite with increasing age; therefore, it is important to keep older people interested in food through the development of a variety of meals and snacks that are both nutritious and appetising.

ACKNOWLEDGEMENTS

Mary Lucas (research assistant) for her assistance in formatting and proofreading the manuscript, and Jessica Greiger (PhD student) for her help with provision of relevant data and referencing.

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Caryl NOWSON

Deakin University, Melbourne, Victoria, Australia

Table 1 Comparison of Daily Nutrient Reference Values for younger and
older adults

                                           EAR (a)
Nutrient                          31-50 years  >70 years

Energy (MJ) (c) (m/f) (d)          10.2/8.7       8.3/7.4
Protein (g) (m/f)                  52/37         65/46
Iron (mg) (m/f)                     6/8           6/5
Zinc (mg) (m/f)                    12.0/6.5      12.0/6.5
Riboflavin (mg) (m/f)               1.1/0.9       1.3/1.1
Vitamin B6 (mg) (m/f)               1.1/1.1       1.4/1.3
Vitamin B12 (mg) (m/f)              2.0/2.0       2.0/2.0
Calcium (mg) (m & f)              840          1100
Vitamin D ([micro]g) (e) (m & f)    5            15

                                           RDI (b)
Nutrient                          31-50 years  >70 years

Energy (MJ) (c) (m/f) (d)
Protein (g) (m/f)                   64/46        81/57
Iron (mg) (m/f)                      8/18         8/8
Zinc (mg) (m/f)                     14.0/8.0     14.0/8.0
Riboflavin (mg) (m/f)                1.3/1.1      1.6/1.3
Vitamin B6 (mg) (m/f)                1.3/1.3      1.7/1.5
Vitamin B12 (mg) (m/f)               2.4/2.4      2.4/2.4
Calcium (mg) (m & f)              1000         1300
Vitamin D ([micro]g) (e) (m & f)

(a) EAR = estimated average requirement (meets the needs of 50% of the
population).
(b) RDI = recommended dietary intake (meets the needs of 98% of the
population).
(c) Estimated energy requirement; mean for men (m) and women (f) aged
31-50 years, height 1.6 m, weight 56.3 kg, physical activity level 1.6.
(d) m/f = male/female.
(e) Adequate intake (when insufficient information available to devise
an EAR).