Population ageing reflects an inevitable and irreversible demographic transition. Ageing is characterized by progressive deterioration in several biological functions along with the natural age-related changes in viability and increased vulnerability1. In general, the term ‘elderly’ or ‘old age’ or ‘senior citizens’ apply to people with ages nearing or surpassing the average lifespan of human beings, which may vary with geography and population groups. Thus, there is no universal cut-off for old age, and it may not convey the same meaning across societies. The measures and indicators commonly used to relate the sizes of different age groups are based on people’s chronological age, stereotypically defining older persons as those aged 60 or 65 yr or over2. According to the World Health Organization (WHO), the number of persons aged 60 yr and above globally was over 1.0 billion in 2019 and this is expected to rise to 1.4 billion by 2030 and 2.1 billion by 20503. According to the United Nations (UN), globally, the number of persons aged 65 yr and above was 703 million in 2019, and by 2050, it is expected to reach 1.5 billion2. The life expectancy at birth during 2015-2020 was 72.3 yr and it is projected to increase by an additional 4.5 yr by 2045-20502.
According to the ‘National Policy on Older Persons’ adopted by the Government of India in January 1999, ‘senior citizens’ or ‘elderly’ are those aged 60 yr and above4. The population in India has nearly tripled in the last 50 yr, and the number of the elderly has increased over four-fold during the same time frame5. In 2019, of the estimated 1.366 billion population of India, the number of aged population (>65 yr) was 87 million, and by 2050, it is expected to reach 225 million2. However, increased longevity is associated with non-communicable diseases (NCDs) and the average annual per capita out-of-pocket health spending in India is almost four times as high for older adults as that of younger adults6.
Ensuring the quality of life, especially in relation to age-related changes and age-associated ailments, among the growing geriatric population is a challenge. Some of these could be minimized, mitigated and/or prevented through appropriate dietary guidelines and nutrient recommendations. For such recommendations to be developed and disseminated, context-specific nutritional requirements must be derived. The existing nutritional requirements, mainly for Indian children and adults, are computed using factorial approach and may not be fully relevant to the elderly. This problem is compounded by the dearth of information on the dietary intakes, nutritional status and physiology of the elderly in India. Against this background, this paper elucidates the nutritional linkages to ageing and argues that there is an imminent need to derive context-specific nutritional requirements for the elderly in India.
Ageing and Nutrition
Ageing is an unavoidable biological process controlled by environmental and genetic factors. Biological ageing is multifactorial and accompanied by a variety of physiological, psychological, economic and social changes, which have a direct bearing on nutritional status and thus the health of the elderly7,8.
Physiological changes associated with ageing include changes in body composition where the proportions of lean body mass (LBM, predominantly the muscle mass and bone mass) as well as bone mineral density decrease, while the proportion of fat mass, particularly visceral fat, increases. The loss of muscle mass and strength (sarcopenia) and bone mass (osteopenia) is a normal age-associated phenomenon. Longitudinal studies demonstrated that resting energy expenditure declines by about 2-4 per cent per decade from 30 to 80 yr with an accelerated decline between 40 and 50 yr9. As a result, the basal metabolic rate (BMR) declines by 10-20 per cent in the elderly as compared to younger adults10, which has a direct bearing on the nutritional requirements. In addition, older people often develop disorders of the gastrointestinal tract, which ultimately limit the digestion, absorption and/or bioavailability of multiple nutrients including vitamins and minerals11. Delayed gastric emptying and decline of olfactory, gustatory and visual food perception in the elderly result in decreased appetite (anorexia of ageing), leading to reduced energy intake, decreased food choices and low diversity in meal composition7. There are several molecular and cellular hallmarks associated with ageing, linked to decline in physical activity and inflammation both of which can be interceded by nutrition. Ageing is also associated with increased risk of NCDs12; this could be a ramification of unavoidable physiological changes and could be accelerated by unhealthy diet, physical inactivity and sedentary life (Figure). Suboptimal nutritional status, particularly deficiency of micronutrients, is a contributing factor to the prevalence and severity of NCDs such as cardiovascular diseases (CVD), cognitive, musculoskeletal, metabolic and ophthalmic diseases13 (Table I)14-28.
Determining nutritional requirements for the elderly: Factors to consider
Nutrition is an important determinant of health among the elderly. The total calorie needs tend to decrease with age because of reduced physical activity and a lower resting metabolic rate (RMR), while the needs for some micronutrients increase with age. Prominent determinants that influence lifespan include environmental factors, and among these, the most important are dietary diversity and physical activity29. Therefore, some of the following factors need careful consideration while determining the nutritional requirements for the elderly.
With ageing, energy requirement gradually decreases because of the changes in LBM, BMR and a reduction in physical activity. In 2010, the Longitudinal Ageing Study in India (pilot) reported that 69 per cent of 1500 older adult respondents in four States had no physical exercise and it further decreased with age and significantly more so among females30. Reduction in physical activity of an individual leads to a reduction in the total energy expenditure and this is one of the important factors contributing to reduced energy requirements among the elderly. Several lines of evidence demonstrate that even in apparently healthy older adults, there is dysregulation of energy intake, thus increasing the risk of energy imbalance31. In the elderly population, especially those with very low energy requirements, the likelihood of their diets not meeting the micronutrient requirements is very high.
During ageing, the body becomes resistant to the normal growth signals shifting the balance towards catabolism and muscle loss, leading to sarcopenia. Inadequate protein intake in the long run can not only accelerate the loss of muscle mass and functional inability but also impair the immune function and wound healing32, while resulting in significant clinical consequences such as frailty, increased risk of falls with associated injuries and fractures leading to death. Therefore, the main anabolic stimulus for skeletal muscle other than exercise is protein intake; hence, protein requirement increases with age33. The European Society for Clinical Nutrition and Metabolism recommends 1.0-1.2 g/kg body weight/day for healthy older people and 1.2-1.5 g/kg/day for older people who are malnourished or with chronic illness34. As energy requirements generally decline with ageing, the dietary protein-to-energy (PE) ratio would become higher among the elderly. Thus, it is the PE ratio that is more important than the protein intake per se. In addition, due to reduced appetite or inability to masticate protein-containing foods such as meat, greater quantity of essential amino acids, particularly branched-chain amino acids such as leucine, isoleucine and valine, is required33.
Adequate carbohydrates, especially complex carbohydrates, need to be provided to protect the protein from being used as an energy source. As per the recommendations, 55-65 per cent of energy should be provided by carbohydrates35. Dietary fat is the source of essential fatty acids and is also required for absorption of fat-soluble vitamins. Monounsaturated and polyunsaturated fats, particularly omega-3-rich fats, should be substituted for saturated fats (SFAs) as these fats help protect the heart and the brain. Therefore, except in cases of overweight or obesity, it is not required to restrict fat intake to <30 per cent of energy for those who are sedentary and 35 per cent of energy for those who are active35. An upper limit of 10 per cent from the energy of SFAs, desirable intakes of n6 PUFA is 4-10 per cent of energy and a ratio of n6/n3 PUFA between 5:1 to 10:1 are recommended35.
Several studies have alluded to the beneficial effects of fibre on physiologic activities (gut transit time, crypt formation and intestinal thickness, bioavailability of minerals and vitamins, protein digestion, cholesterol and other lipid metabolism, glycaemic and insulinaemic responses and immune response) in the elderly36. Since older people have a greater proportion of fat mass to lean muscle mass and the water content of fat mass is lesser than the muscle mass, the elderly are more likely to become dehydrated. Impaired thirst and physical limitations tend to reduce water intake. Therefore, the elderly should be encouraged to consume water frequently. Daily fluid needs for the healthy older adults are approximately 30 ml/kg body weight, with a minimum of 1.5 l/day or 1 to 1.5 ml/kilocalorie consumed37. Adequate fibre, along with adequate fluid, not only helps maintain normal bowel function but also reduces the risk of intestinal inflammation.
With the reduction in energy requirements and the lower intake of food along with the impaired absorption, metabolism and utilization, deficiency of certain micronutrients is more likely to occur in the elderly. Epidemiological evidence suggests that there is a clear association between subclinical micronutrient deficiencies and acceleration of the natural ageing process as well as several chronic age-related diseases (Table I). Conversely, adequate micronutrients can play an important role in healthy ageing and each of them needs a different approach and consideration for defining the requirements. For instance, vitamin A (VA) improves vision; contributes to proper functioning of the digestive system, urinary tract and immune function and protects skin in the elderly. Its requirements are factorially computed considering the catabolic loss, liver stores, liver-to-body weight ratio, total body store versus liver stores, efficiency of storage and the dietary beta-carotene conversion to VA35,38. Since many of these factors are expected to alter during normal ageing process, there is a need to systematically review these for determining VA requirements in the elderly.
Vitamin D (VD) deficiency is today considered as a worldwide epidemic, more so in the elderly, as a result of decreased sunlight exposure (particularly in institutionalized older adults), decreased intrinsic synthesis of VD metabolites, increased parathyroid hormone as well as age-related changes in body composition, lower dietary intake and decreased VD receptor activity39. Furthermore, the kidney’s ability to convert 25-hydroxy VD into 1, 25-dihydroxy VD is reduced, and the absorption of VD from the gut is also decreased. Low VD levels are related to the risks of fractures, falls, reduced muscle strength, low physical performance, impaired cognitive function and depression in older adults 40,41.
The association between poor thiamine (B1) status and neurodegenerative diseases, cognitive impairment and depression25 is well established. In the elderly, riboflavin (B2) supplementation is effective in lowering high amounts of homocysteine (Hcys) in the blood42. Vitamin B6 occurs as pyridoxine, pyridoxal-5’-phosphate (PLP) and pyridoxamine. Pyridoxamine is a potent inhibitor of advanced glycation end products (AGEs) by sequestering the glucose and reactive products of glucose and lipid degradation. The AGEs are the main culprits in many age-related disorders43. Low PLP levels may decrease the production of glutathione and impair the antioxidant defence system. Pyridoxine is required for the metabolism of several neurotransmitters, including dopamine, serotonin and histamine, essential in brain health. Vitamin B9 (folate), along with vitamins B12 and B2, plays an important role in the metabolism of Hcys. In older adults, hyperhomocysteinaemia is an independent risk factor for CVD44. Supplementation of folate can bring down the elevated Hcys levels. In the elderly, the consumption of foods rich in B12 (animal foods) can decrease with age due to poor dentition and dysphagia. Malabsorption of food-bound cobalamin is the prime cause of low B12 status in the elderly. This could stem from a variety of reasons including decrease in gastric acid secretion, lack of intrinsic factor, bacterial overgrowth or defects in the cobalamin uptake system45.
In the elderly, zinc (Zn) also plays a pivotal role in immune response as well as in neurological functions. A reduced capacity to absorb Zn, increased likelihood of disease states that alter Zn utilization and increased use of drugs that lead to higher Zn excretion may contribute to an increased risk of mild Zn deficiency in older adults. Deficiency of Zn may cause dermatitis, diarrhoea, impaired wound healing, decreased appetite and impaired taste and is also associated with Alzheimer’s disease15 and age-related macular degeneration14. Malnourished elderly are at an increased risk of iron (Fe) deficiency due to inadequate dietary intake, chronic gastrointestinal blood loss, low absorption (due to atrophic gastritis) and bioavailability46,47. However, only about 15-50 per cent anaemia among the elderly is associated with iron deficiency, while the other causes of anaemia remain unknown46,48. This could be due to age-dependent decline in blood haemoglobin levels among healthy adults as results of reduced lean mass and tissue functions49. Excess intake of Fe increases the risk of type 2 diabetes as it induces insulin resistance and modifies the glucose transport in adipocytes50. These observations together suggest that iron metabolism during ageing is distinct compared to adulthood.
Calcium (Ca) is central in many physiological processes, and requirements for Ca increase with age as there is decreased intestinal absorption of Ca and VD, decreased circulation of gonadal hormones, increased excretion of urinary Ca and decreased physical activity. However, Ca absorption is dependent on VD intake as it facilitates the intestinal absorption of Ca. Calcium deficiency is linked to the development of osteopenia, osteoporosis and fractures51. Reduced glomerular filtration rate is yet another important factor associated with ageing that can eventually affect the renal conservation of Ca and result in secondary hyperparathyroidism, which is a potential cause for significant bone loss. Absorption of Ca decreases with age and the fractional Ca absorption declines by about 0.21 per cent per year after 40 yr of age52.
The sensitivity of BP to sodium chloride intake increases with age and also accounts for reduced renal and cardiovascular functions in older adults53. Potassium (K) not only aids in the acid-base balance, but also contributes to generation of transmembrane electrochemical potentials required for the nerve fibres and muscle cells. While the relationship between K intake and BP is known54, high intake of K from foods, especially when it is associated with bicarbonate precursors, is linked to decreased bone loss55.
Current recommendations and the need for deriving India-specific nutritional requirements for the elderly
The ICMR Expert Group on Nutrient Requirements35 has revised the nutrient requirements and recommended dietary allowances (RDA) for Indians by employing the latest state-of-the-art methodological framework in harmony with the dietary reference intake recommendations of international organizations like FAO/WHO/UNU (Food and Agriculture Organization/World Health Organization/United Nations University). The latest ICMR-2020 recommendations include three important dietary reference values (specific to age, gender and physiological groups): estimated average requirements (EAR), RDA and tolerable upper intake level (TUL). While the EAR is an average requirement of population, RDA is sufficient to meet the requirements of nearly all (97.5%) healthy individuals in a particular life stage and gender group. The TUL is derived from toxicological framework; the intake beyond this level increases the risk of toxicity. In addition, ICMR-EAR-RDA (2020) also suggested assessing the population dietary inadequacy against the requirement distribution38,56. A factorial approach, where the losses and additional requirements for growth and their associated variance are summed to generate the physiological requirement distribution per kilogram body weight, was adopted during formulation of the aforementioned recommendations with a few exemptions. For example, in the case of energy, the actual energy expenditure was considered, whereas functional attributes were considered for some vitamins (B-vitamins). These requirements were then adjusted for bioavailability, age, gender and physiological group-specific reference body weight to derive the dietary requirements.
However, as outlined in the preceding section, age-related physiological and sensory changes could potentially compound the requirements in the elderly, and thus, more evidence-based nutrient requirement recommendations need to be derived and adopted. For example, the ICMR (2020) recommendations for energy and VD for the elderly are lower and higher, respectively35 (Table II). These are based on the postulates that the energy requirement will decrease by 100 and 70 Kcal per decade for men and women, respectively, while increased VD was recommended considering the higher need of VD to prevent age-associated osteopenia and high prevalence of VD deficiency among the elderly population in India. Similarly, such an exercise is required for deriving the dietary requirements of other nutrients for the elderly in India.
Alternatively, the other available nutritional requirements for the elderly which are internationally adopted are the Institute of Medicine (IOM; now The National Academy of Medicine) guidelines. The IOM came out with the report on dietary reference intakes in 200657 and another one in 201158 for people >50 yr of age. These reference intakes were formulated keeping in view the growing public concerns over diet quality of the elderly, and a careful assessment of data on how dietary needs change with ageing, and which nutrients, in particular, are important for the ageing populations, and the challenges faced in consumption of high-quality diets. However, adequate caution should be exercised in adopting these recommendations as these are not context-specific and the age >50 yr does not actually represent the elderly category. Similarly, the European Food Safety Authority (EFSA) has also made recommendations for different age and physiological groups59. Although EFSA’s recommendations are more recent, they do not provide any specific recommendations for the elderly.
The elderly population in India has increased over four-fold in the last 50 years5. Ensuing health span (i.e. maintaining health and functional capacity) rather than mere lifespan of the elderly needs attention from the point of optimal nutrition. An important step in achieving this is through practicable dietary guidelines based on scientifically developed context-specific nutritional requirements. As we set out the way forward, the following factors need consideration (Box & Table III).
Financial support & sponsorship: Author (GBR) was supported by grants from the Indian Council of Medical Research (F.N.5/9/1447/2021-Nutr) and the Department of Biotechnology ((BT/PR36689/PFN/20/1524/2020), New Delhi.
Conflicts of Interest: None.
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