Editing Human nutrition (section)

=== Elderly nutrition ===
[[Malnutrition]] in older adults is a significant health concern, linked to increased [[Mortality rate|mortality]], [[morbidity]], and physical decline, which adversely impacts daily activities and overall quality of life. This condition is common among the elderly and can also contribute to the development of [[Geriatrics|geriatric]] syndromes.<ref name="norman-2021">{{Cite journal | last1=Norman | first1=Kristina | last2=Haß | first2=Ulrike | last3=Pirlich | first3=Matthias | date=2021-08-12 | title=Malnutrition in Older Adults—Recent Advances and Remaining Challenges | journal=Nutrients | language=en | volume=13 | issue=8 | pages=2764 | doi=10.3390/nu13082764 | doi-access=free | issn=2072-6643 | pmc=8399049 | pmid=34444924}}</ref> In older adults, malnutrition is typically indicated by unintentional weight loss or a low [[body mass index]], though hidden deficiencies, such as those involving micronutrients, are often harder to detect and frequently go unnoticed, especially in community-dwelling seniors. This is generally higher among the elderly, but has different aspects in [[Developed country|developed]] and [[undeveloped countries]].<ref name="Chwang">{{Cite journal | title=Nutrition and dietics in aged care | last=Chwang | first=Leh-Chii | journal=Nutrition and Dietics | doi=10.1111/j.1747-0080.2012.01617.x | date=September 2012 | issue=3 | volume=69 | pages=203–207}}</ref> In developed countries, the most common cause of malnutrition is [[illness]], as both [[Acute (medicine)|acute]] and [[chronic condition]]s can lead to or worsen nutritional deficits. As age increases the likelihood of disease, older adults are at the highest risk for nutritional challenges or malnutrition. The causes of malnutrition are complex and multifaceted, with aging processes further contributing to its development. The concerns faced with nutritional markers for the elderly are highlighted by the prevalence and determinants of malnutrition in adults over 65, encompassing factors from age-related changes to disease-related risks. The challenges in addressing, understanding, identifying, and treating malnutrition is key, noting that in some cases, targeted supplementation of [[Macronutrients|macro-]] and [[micronutrient]]s may be necessary when diet alone does not meet age-specific nutritional needs.<ref name="norman-2021" />

[[World Health Organization|The World Health Organization]] (WHO) has identified healthy aging as a key priority from 2016 to 2030, developing a policy framework that advocates for action across multiple sectors.<ref name="norman-2021" /> The program aims to help older adults (those aged 65 and over) maintain functional ability, ensuring their well-being and active participation in society. Older adults are the fastest-growing age group, and [[United Nations]] projections indicate that by 2050, their numbers will double those of children under five and exceed the population of adolescents aged 15 to 24. By 2050, global life expectancy, which was 72.6 years in 2019, is expected to increase by approximately five years.<ref name="norman-2021" /> Maintaining good nutritional status and adequate nutrient intake is essential for health, quality of life, and overall well-being in older age, and it plays a crucial role in healthy aging as defined by the WHO.<ref>{{Cite journal | last1=Lee | first1=Jenny Jinyoung | last2=Sultana | first2=Nargis | last3=Nishita | first3=Christy | date=2024-04-02 | title=Participant Assessment of an Alternative Flexible Congregate Nutrition Meal Program for Older Adults | journal=Journal of Nutrition in Gerontology and Geriatrics | language=en | volume=43 | issue=2 | pages=134–150 | doi=10.1080/21551197.2024.2367972 | pmid=38915295 | issn=2155-1197 | doi-access=free}}</ref>

==== Elderly Nutrition: Protein ====
While energy needs decrease with age, the demand for [[Protein (nutrient)|protein]] and certain nutrients actually rises to support normal bodily functions. Deficiencies in specific nutrients are also linked to [[cognitive decline]], a common issue among older adults. Reduced daily food intake in the elderly often leads to insufficient protein consumption, contributing to [[sarcopenia]], a condition marked by the loss of muscle mass. Approximately 30% of those aged 60 and above, and over 50% of individuals aged 80 and older, are affected by this condition. The inability to meet protein needs exacerbates health issues, including chronic muscle wasting and bone health deterioration, leading to functional decline and frailty.<ref name=":0">{{Cite journal | last1=Kaur | first1=Damanpreet | last2=Rasane | first2=Prasad | last3=Singh | first3=Jyoti | last4=Kaur | first4=Sawinder | last5=Kumar | first5=Vikas | last6=Mahato | first6=Dipendra Kumar | last7=Dey | first7=Anirban | last8=Dhawan | first8=Kajal | last9=Kumar | first9=Sudhir | date=2019-09-25 | title=Nutritional Interventions for Elderly and Considerations for the Development of Geriatric Foods | url=http://www.eurekaselect.com/172217/article | journal=Current Aging Science | language=en | volume=12 | issue=1 | pages=15–27 | doi=10.2174/1874609812666190521110548 | pmc=6971894 | pmid=31109282}}</ref> To mitigate this, older adults are advised to evenly distribute protein intake across meals—breakfast, lunch, and dinner. As aging diminishes the body's ability to synthesize muscle protein, consuming adequate [[essential amino acid]]s, especially [[leucine]], is crucial. A leucine intake of at least 3&nbsp;g per meal, achieved through 25-30g of high-quality protein, is necessary for effective muscle [[protein synthesis]].<ref name=":1">{{Cite journal | last1=Putra | first1=Christianto | last2=Konow | first2=Nicolai | last3=Gage | first3=Matthew | last4=York | first4=Catherine | last5=Mangano | first5=Kelsey | date=2021-02-26 | title=Protein Source and Muscle Health in Older Adults: A Literature Review | journal=Nutrients | language=en | volume=13 | issue=3 | pages=743 | doi=10.3390/nu13030743 | doi-access=free | issn=2072-6643 | pmc=7996767 | pmid=33652669}}</ref>

Data from the [[National Health and Nutrition Examination Survey]] III indicates that the average protein intake among the elderly is 0.9g/kg of body weight per day, with half of this intake occurring at dinner. This uneven distribution can lead to sub-optimal protein synthesis and increased use of dietary amino acids for other processes like fat storage. Therefore, evenly distributing 30&nbsp;g of protein throughout the day is recommended to enhance protein turnover and prevent muscle loss. Older adults, particularly those with [[Acute illness|acute]] or [[chronic illness]]es, may require higher protein intake, ranging from 1.2 to 1.5g/kg per day, due to a reduced [[Anabolic reaction|anabolic response]]. Some studies suggest that an intake of 1&nbsp;g/kg per day is sufficient, while others recommend 1.3 to 1.73g/kg per day for better health outcomes. Research shows that muscle mass preservation is more effectively supported by animal protein, which has a higher essential amino acid content, than by plant protein. The timing of protein intake, protein source, and amino acid content are key factors in optimizing protein absorption in the elderly.<ref name=":0" /><ref name=":1" />

==== Elderly Nutrition: Zinc ====
[[Zinc in biology|Zinc]] is a vital micronutrient that plays a crucial role in enzymatic [[catabolism]], immune cell function, [[DNA synthesis]], and various micronutrient metabolisms. In the elderly, low serum zinc levels have been reported, which weakens the immune system, making them more susceptible to infections and increasing their risk of morbidity. Aging impairs [[T cell]] function, particularly due to zinc deficiency, and the reduced synthesis of [[metallothionein]] disrupts zinc balance in the gut and other tissues.<ref name=":3">{{Cite journal | last1=Mocchegiani | first1=Eugenio | last2=Romeo | first2=Javier | last3=Malavolta | first3=Marco | last4=Costarelli | first4=Laura | last5=Giacconi | first5=Robertina | last6=Diaz | first6=Ligia-Esperanza | last7=Marcos | first7=Ascension | date=June 2013 | title=Zinc: dietary intake and impact of supplementation on immune function in elderly | journal=AGE | language=en | volume=35 | issue=3 | pages=839–860 | doi=10.1007/s11357-011-9377-3 | issn=0161-9152 | pmc=3636409 | pmid=22222917}}</ref> This deficiency is primarily due to inadequate dietary zinc intake, compounded by factors such as poor [[mastication]], oral health issues, medication use that interferes with absorption, and psychosocial factors that limit food intake. Additionally, [[Epigenetics|epigenetic]] changes like DNA [[methylation]] may impair zinc transporters, leading to decreased zinc absorption as people age. Structural changes in the gut, including altered villus shape, [[Mitochondrion|mitochondrial]] changes, crypt elongation, [[collagen]] alterations, and increased cell replication time in the crypts, also significantly affect zinc absorption in the elderly.<ref name=":0" /><ref>{{Cite journal | last=Cabrera | first=Ángel Julio Romero | date=January 2015 | title=Zinc, aging, and immunosenescence: an overview | journal=Pathobiology of Aging & Age-related Diseases | language=en | volume=5 | issue=1 | pages=25592 | doi=10.3402/pba.v5.25592 | issn=2001-0001 | pmc=4321209 | pmid=25661703}}</ref>

The recommended daily allowance of zinc is 11&nbsp;mg for older men and 8&nbsp;mg for older women, with an upper tolerable limit of 25–40&nbsp;mg per day, including both dietary and supplemental sources. However, individuals over 60 often consume less than 50% of the recommended zinc intake, which is crucial for proper body function. Data from the Third Health and Nutrition Survey in the United States revealed that only 42.5% of adults over 71 years old met adequate zinc intake levels, with many suffering from zinc deficiency. To reach the upper tolerable limit of 40&nbsp;mg per day, zinc intake from both food and supplements must be considered to help normalize serum zinc levels in deficient elderly individuals. Dietary sources such as [[seafood]], [[poultry]], [[red meat]], [[bean]]s, [[fortified cereals]], [[whole grain]]s, [[Nut (fruit)|nuts]], and [[dairy product]]s are beneficial for maintaining adequate zinc levels, though absorption is higher from animal proteins than plant-based sources.<ref name=":0" /><ref name=":3" />

==== Elderly Nutrition: Vitamin-B Complex ====
The [[Vitamin b complex|Vitamin-B complex]], which includes eight water-soluble vitamins, plays a crucial role in maintaining cellular function and preventing brain atrophy. Among the elderly, deficiencies in vitamins [[Vitamin B12|B12]], [[Vitamin B6|B6]], and [[folate]] are linked to cognitive decline and depressive symptoms.<ref name=":4">{{Cite journal | last1=Ali | first1=Mennatallah A. | last2=Hafez | first2=Hala A. | last3=Kamel | first3=Maher A. | last4=Ghamry | first4=Heba I. | last5=Shukry | first5=Mustafa | last6=Farag | first6=Mohamed A. | date=2022-09-22 | title=Dietary Vitamin B Complex: Orchestration in Human Nutrition throughout Life with Sex Differences | journal=Nutrients | language=en | volume=14 | issue=19 | pages=3940 | doi=10.3390/nu14193940 | doi-access=free | issn=2072-6643 | pmc=9573099 | pmid=36235591}}</ref>

The Recommended Dietary Allowance (RDA) for vitamin B12 is 0.9-2.4 μg/day, while the estimated average requirement in the U.S. and Canada is 0.7-2 μg/day. Elderly individuals with plasma vitamin B12 levels below 148 pmol/L are considered severely deficient, and those with levels between 148 and 221 pmol/L are marginally deficient. A deficiency in these B-vitamins, particularly B6, B12, and folate, is associated with elevated [[homocysteine]] levels, which increase the risk of [[alzheimer's disease]] and [[dementia]]. Increased intake of these vitamins can lower homocysteine levels and reduce the risk of these conditions.<ref name=":4" /> According to the [[National Health and Nutrition Examination Survey]], about 6% of elderly Americans over 70 are severely deficient in vitamin B12, and more than 20% of those over 60 are mildly deficient. This deficiency is often due to insufficient food intake and [[malabsorption]] caused by degenerative digestive conditions, as indicated by elevated plasma [[gastrin]] levels in older adults. The deficiency of vitamin B6 among institutionalized elderly in Europe ranges from below 1% to 75%. B-vitamins are primarily found in animal-based foods, making deficiencies more common among those with limited animal food intake due to cultural, religious, or economic reasons. For vegetarians, fortified foods can be a viable alternative to ensure adequate vitamin B12 levels, especially when reducing laxative use to improve absorption.<ref name=":0" />

==== Elderly Nutrition: Calcium & Vitamin D3 ====
Aging is often marked by a decline in [[bone mineral density]], leading to an increased risk of [[osteoporotic fracture]]s and reduced mobility, especially among elderly women. Women experience greater bone loss, around 2-3% per year, particularly after [[menopause]] due to [[estrogen deficiency]]. This deficiency reduces intestinal calcium absorption, decreases calcium reabsorption by the kidneys, and increases [[parathyroid hormone]] secretion, all contributing to [[bone resorption]]. Additionally, [[Vitamin d3|vitamin D3]] deficiency, common in older adults due to reduced skin synthesis and limited sun exposure, further disrupts [[Calcium in biology|calcium]] [[homeostasis]] by decreasing intestinal absorption of calcium.<ref name=":5">{{Cite journal | last1=Meehan | first1=Meghan | last2=Penckofer | first2=Sue | date=2014-07-25 | title=The Role of Vitamin D in the Aging Adult | url=http://savvysciencepublisher.com/jms/index.php/jag/article/view/245 | journal=Journal of Aging and Gerontology | volume=2 | issue=2 | pages=60–71 | doi=10.12974/2309-6128.2014.02.02.1 | issn=2309-6128 | pmc=4399494 | pmid=25893188}}</ref> As kidney function declines with age, the conversion of vitamin D3 to its active form is impaired, exacerbating the deficiency.

Serum 25(OH)D levels below 50 nmol/L are linked to muscle weakness and reduced physical function, while levels below 25-30 nmol/L increase the risk of falls and fractures. Older adults typically consume less calcium, around 600&nbsp;mg/day, which heightens their susceptibility to fractures. For optimal bone health, a calcium intake of 1000–1200&nbsp;mg/day is recommended, along with 800 IU/day of vitamin D3 for those with adequate sun exposure, and up to 2000 IU/day for those with limited sun exposure or obesity. However, dietary factors like [[phytates]], [[oxalate]]s, [[tannin]]s, and high sodium can impair calcium absorption and retention, underscoring the need to maintain sufficient levels of both calcium and vitamin D3 through diet or supplementation to reduce the risk of [[pathologic fracture]]s.<ref name=":0" /><ref name=":5" />

==== Elderly Nutrition: Iron ====
[[Iron deficiency]] is prevalent among the elderly and is a significant contributor to [[anemia]] in this population. As people age, the body's ability to balance iron storage and supply diminishes, leading to this condition. Multiple factors contribute to iron deficiency in older adults, including reduced food intake, frequent medication use, gastrointestinal malabsorption, and occult bleeding. [[Malabsorption]] can also result in excessive iron accumulation, further complicating the issue. Age-related anemia may also be linked to increased levels of [[hepcidin]], a hormone that reduces iron absorption in the intestine, leading to low iron levels.<ref name=":2">{{Cite journal | last1=Fairweather-Tait | first1=Susan J. | last2=Wawer | first2=Anna A. | last3=Gillings | first3=Rachel | last4=Jennings | first4=Amy | last5=Myint | first5=Phyo K. | date=March 2014 | title=Iron status in the elderly | journal=Mechanisms of Ageing and Development | language=en | volume=136-137 | pages=22–28 | doi=10.1016/j.mad.2013.11.005 | pmc=4157323 | pmid=24275120}}</ref>

The [[recommended daily intake]] of iron for both men and women is 8&nbsp;mg, with an upper limit of 45&nbsp;mg/day. According to the [[World Health Organization]], [[hemoglobin]] levels below 12&nbsp;g/dl in women and 13&nbsp;mg/dl in men indicate anemia.<ref name=":2" /> The [[NHANES]] III survey found that anemia affects 10.2% of women and 11% of men over 65, with prevalence increasing with age. Low iron levels not only decrease quality of life but are also associated with [[Depression (mood)|depression]], [[fatigue]], [[cognitive impairment]], and [[muscle wasting]].

Dietary components significantly influence iron absorption; tannins and [[polyphenol]]s in tea and coffee inhibit it, while [[Vitamin C]] enhances it. However, the interaction between iron and vitamin C can generate [[free radicals]], particularly in cases of [[iron overload]]. In iron deficiency, vitamin C aids absorption. [[Aspirin]] use in the elderly, often for cardiovascular disease, is linked to lower serum [[ferritin]] levels. Iron deficiency can be managed through an iron-rich diet or supplementation. Severe iron deficiency anemia may require oral iron therapy, typically with 300&nbsp;mg of [[ferrous sulfate]] containing 60&nbsp;mg of elemental iron. For those who do not respond to oral treatment, [[intravenous iron infusion]] or [[iron chelation]] for iron overload may be necessary.<ref name=":0" />