A Deep Dive into Common Dietary Hardships Facing Patients of Advanced Age, and the Subsequent Deficiencies That Should Be Addressed in This Cohort
The biological process of aging is defined by various physical, physiological, and cognitive changes in the body.[1] Cellular and biological changes present additional challenges for those of advanced age, often contributing to diminished function. Proper nutrition is a significant determinant of successful aging, with inadequate nutritional intake resulting in the progression of multiple chronic diseases prevalent in the aged population.[2] However, factors like decreased absorption rates, reduced food intake, and alterations to metabolism can make it difficult for seniors to achieve the proper nutrient status essential for preventing disease.
The Challenge: Reduced Food Intake
Many patients of advanced age experience a loss of appetite and a decline in the ability to ingest adequate nutrients. This physiologic and unintentional reduction of food intake is referred to as anorexia, and it significantly affects approximately 25% of the older population.[3] This process is due to a combination of sensory impairment, hormonal changes, and changes within the GI tract itself.
As age advances, gustatory and olfactory function decline. Changes in the olfactory epithelial cells can lead to anosmia, or a reduced sense of smell.3 Along similar lines, the number of taste buds and sensitivity of the papillae on the tongue decrease as we age.3 Because of this, individuals of advanced age often experience a reduced sense of taste. One study revealed that more than 60% of people over 65 years old and 80% of people over 80 years old experience a reduction in taste.[4] The decrease in taste and smell can lead to overall dissatisfaction with food consumed and a reduced desire to eat.[5] To achieve a desirable taste profile, those with impaired senses can desire foods higher in sugar and fat, often at the expense of necessary nutrients.5
Hormonal changes can also contribute to reduced food intake and dissatisfaction with meals. Cholecystokinin (CCK), the hormone that provides a sensation of satiety, increases with age.[6] Higher CCK levels lead to early satiety and difficulty completing meals. Additionally, ghrelin, the hormone that leads to hunger and enhances gastric emptying, decreases with age, further contributing to anorexia and reduced nutrient load.6
The Challenge: Absorption
Consuming less food, and therefore reducing nutrient load, is compounded by the fact that changes in gastrointestinal function may contribute to an even further reduction of nutrient absorption in old age. Aging is associated with slowed gastric motility, decreased gastric secretions, and impaired gallbladder contraction.1 Each of these factors is paramount to proper digestion and assimilation of nutrients. Functional deficiencies can further reduce food intake due to the uncomfortable sensations of indigestion and early satiety.
Hypochlorhydria, or a reduction in stomach acid, is prevalent in the senior population.[7] This contributes to decreased absorption of vital micronutrients, such as iron and vitamin B12. Decreases in gastric acid secretion contribute to dysbiosis, further contributing to gastrointestinal malabsorption and poor assimilation of nutrients.[8]
Saliva amounts, which play a significant role in taste, mastication, digestion, and desire for food, decrease in advanced age.[9] Saliva provides the lubrication needed to begin the mechanical breakdown of food. The production of digestive enzymes begins in saliva to initiate the digestive process as the meal, or even just the thought of the meal, commences. There is also a reduction in digestive enzyme production throughout the GI tract as age advances, making the breakdown and assimilation of nutrients especially challenging.7
Macro- and Micronutrients That Deserve Special Attention in Seniors
Unfortunately, physiological factors contribute to an overall poorer nutritional makeup in seniors, yet they are a population with significant nutrient needs. Many degenerative diseases associated with aging have direct ties to nutrient deficiencies.[10]
Protein
While overall energy expenditure and requirements decline with age, the need for adequate protein does not.[11] Patients of advanced age experience impaired protein turnover and metabolic alterations that negatively impact the ability to produce muscle protein, leading to sarcopenia (a syndrome characterised by progressive and generalised loss of skeletal muscle mass and strength).[12] The reduced daily food intake that many older people have means that many fall below their recommended daily intake of protein, resulting in muscle mass loss or sarcopenia, which contributes to increased incidence of disability and mortality.[13] About 30% of individuals over the age of 60 and more than 50% of individuals over the age of 80 are sarcopenic.[14]
Recent research points to an increased need for protein in the senior population and even suggests that the current RDA dietary recommendation of 0.8 g/kg/day of protein does not adequately fulfill the requirements of the elderly.[15] Older adults experience an impaired anabolic response to protein, which is the basis for their increased demand. Research suggests that total protein intake should be between 1.0 to 1.2 g/kg/day in advanced age. Older individuals with chronic disease or poor health status may have an even higher demand of up to 1.2 to 1.5 g/kg/day.15 A study by Volpi et al. found that the essential amino acids, particularly leucine, were of utmost importance for those at risk of muscle wasting, as leucine has a stimulatory effect on the synthesis of muscle protein. Keeping leucine intake above 3 g/day is ideal for supporting sufficient muscle mass.15 Data suggests that regularly consuming protein three times throughout the day, rather than all in one meal, leads to better protein assimilation.14 There is also evidence that amino acid supplementation can enhance protein absorption in this group when necessary.11 It should be noted that, for individuals who have chronic kidney disease, 0.6 to 0.8 g/kg/day of protein is recommended.[16]
In addition to causing sarcopenia, reduced protein intake can adversely affect bone health, leading to frailty.4 Older people, particularly women, are of significant risk for osteopaenia and osteoporosis, adding more importance to ensuring adequate protein intake for these individuals.
Vitamin D3
While protein deficiencies can contribute to bone loss, vitamin D deficiencies are an even more significant factor for bone health. Unfortunately, the risk for vitamin D deficiency increases as age advances.[17] Vitamin D acts as a hormone essential for calcium absorption and bone mineralisation necessary to support proper bone mineral density.[18] Vitamin D deficiency also increases parathyroid hormone levels, which subsequently promotes bone loss.[19]
Older people have a decreased ability to synthesise vitamin D in the skin. Aging skin leads to a fourfold reduction in the skin’s own vitamin D production during sun exposure compared to younger skin.[20] Additionally, with age, the kidneys become much less efficient at converting 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D, or the active form of cholecalciferol.[21] Low vitamin D levels are associated with muscular weakness and increased susceptibility to falls and fractures, with 80% of elderly hip-fracture patients being deficient in vitamin D.21
Supplemental vitamin D dosages can vary depending on factors like sun exposure, but the literature suggests that an intake of approximately 2,000 IU/day will be sufficient for most adults of advanced age.[22] However, multiple randomized intervention trials have seen a significant reduction in falls and hip fractures after supplementing just 1,000 IU/day of vitamin D compared to placebo.[23]
Vitamin D is also integral to overall immune function. Older adults have an increased incidence of infectious disease and can experience longer recovery times and higher mortality rates from these infections.[24] Seniors experience reduced cell-mediated immune response, a process that is highly dependent upon nutritional status. Vitamin D can modulate the innate and adaptive immune responses and decrease the incidence of infection.[25] Alternatively, vitamin D deficiency is tied to increased susceptibility to infection and more frequent onset of autoimmune disease.[26]
Zinc
Zinc is a cofactor for around 300 enzymes[27] and is involved in many metabolic processes, including enzymatic catabolism, DNA synthesis, signal transduction for immune cells, and more.[28] Seniors may experience zinc deficiencies for multiple reasons, including improper dietary intake.[29] Several common medications in this population can alter the physiology of absorption, contributing to lowered overall zinc levels.[30] Altered villus shape and alterations in intestinal microvilli and enterocytes in the large intestine decrease the ability to absorb zinc.4 One research group hypothesised that zinc transporters were impaired in the elderly due to DNA methylation, further contributing to the possibility of deficiency.[31]
Zinc is commonly known as an immune-supportive micronutrient because of its effect on immune mediators. T cell–mediated functioning is impaired without sufficient zinc, leading to a depressed immune function.29 This is particularly dangerous among the elderly population, making seniors more susceptible to infections and increasing their risk for overall morbidity.
Zinc deficiency can also contribute to further nutrient deficiencies, as it’s involved in nutrient transport and synthesis. For instance, zinc is required to make Retinol-Binding Protein (RBP), the protein responsible for transporting vitamin A to the plasma and mobilising retinol from the liver.[32] Proper zinc status also supports the intestinal absorption of vitamin E and folate from dietary sources.31 Additionally, zinc deficiencies contribute to mood disorders,[33] and a loss of taste, some of the issues contributing to further nutritional struggles through reducing food intake.[34]
Iron
Iron deficiency is widespread among older people. Over 10% of adults older than 65 are categorised as anaemic. These rates increase as age advances, with anaemia rates closer to 30% in men over 85 years old and 17% of women in the same bracket.[35] Iron-deficiency anaemia is associated with depression, fatigue, loss of muscle capacity, and impaired cognition, each of which is a common health issue in the elderly.[36] In older people, anemia can lead to a deterioration of existing chronic conditions, progress frailty status, and reduce physical performance and mobility, increasing the risk for falls.[37] Additionally, iron deficiency can contribute to a decline in cognitive function.[38] Iron deficiency in the elderly is an independent risk factor for increased mortality and morbidity and is associated with more prolonged hospitalisations and a higher risk of disability.[39]
As previously mentioned, a decrease in stomach acid contributes to the malabsorption of iron.[40] Additionally, decreased appetite and, consequently, decreased meat consumption can also contribute to deficient states. As we age, we also have increased difficulty maintaining a balance between iron store and iron supply, further exacerbating iron-deficiency anaemia. Hepcidin, a hormone that decreases iron absorption in the intestine to balance iron levels, increases in old age.[41] This results in reduced iron absorption and more iron accumulation, contributing to anaemia and more reactive oxygen species.35
Iron status is of particular importance within the older community. Even mild iron-deficiency anaemia or “low-to-normal” haemoglobin (Hb) levels can contribute to poorer health outcomes and quality of life in the elderly.[42] Geriatric heart-failure patients with low-to-normal Hb levels experience poorer haemodynamics, a more significant symptom profile, and greater mortality.42 Other serious ailments more common in older patients, such as cancer and infectious diseases, have increased mortality rates when associated with lower Hb levels as well.35
B Vitamins
B vitamin deficiencies, particularly those in vitamin B12, B6, and folate, negatively affect cognition and mood.[43] Deficiencies in these vitamins can lead to elevated homocysteine levels, increasing the risk of developing dementia and Alzheimer’s disease, which are common concerns in the aging population.4 Increasing the levels of these vitamins leads to lower homocysteine levels and can reduce the risk of diseases of impaired cognition in advanced age.[44]
Elevated homocysteine has been linked to impaired cognition, both with and without the presence of dementia.[45] The two hallmark pathologies required for diagnosing Alzheimer’s disease are deposits of β-amyloid peptide and the presence of phosphorylated microtubule-associated protein tau.[46] Homocysteine facilitates these processes, which explains its high correlation with cognitive deficits.43 Elevated homocysteine levels also accelerate cell aging, leading to further decline.
The challenge with these vitamins is that absorption becomes an issue with advanced age. Decreased gastric acid secretion and intrinsic factor make B12 assimilation far more difficult.[47] In addition, the use of laxatives, common in the senior population due to altered digestive function and reduced peristalsis, negatively affects the absorption of all B vitamins in the digestive tract.[48] These vitamins are most commonly found in leafy green vegetables, with B12 readily available in high-quality meat sources. Senior patients may struggle with getting enough of these quintessential nutrients from the diet if they are currently experiencing a reduced overall food intake or a reduction in nutrient-dense foods. With more than 20% of the population over age 60 being deficient in vitamin B12, supplementation may benefit patients in this age group.[49]
Many diseases that we commonly associate with advanced age have ties to nutrition status. Unfortunately, the symptoms of individual nutrient deficiency can often mimic symptoms associated with aging, such as fatigue, weakness, and cognitive decline, which can contribute to oversight by the physician when it comes to nutritional intervention. However, proper attention to the nutrient status of the elderly is of utmost importance for quality of life and morbidity. Prevention and treatment of common conditions among them should focus on nutrition, as adequate nutrient load is required to maintain proper health. It is imperative to consider the challenges that patients in this population may face when it comes to proper nutrition and to aid them in overcoming these challenges through diet. In many cases, nutrient supplementation is needed to improve health outcomes.
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