Editing Human nutrition (section)

==== 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" />