Vitamin D and bone health in the elderly

Abstract

The state of vitamin D nutrition depends on synthesis in the skin under the influence of sunlight as well as on dietary intake. In European countries that do not fortify milk with vitamin D, reduced sun exposure is the major factor leading to a fall in body stores of vitamin D with age and to a high frequency of hypovitaminosis D in the elderly sick. In the US, because vitamin D is added to milk and the use of vitamin D supplements is more common, the dietary intake of vitamin D is relatively more important than in Europe, and the total vitamin D intake and body stores of vitamin D are generally higher. Nevertheless, body stores of vitamin D probably fall with age in the US as they do in Europe, and it is likely that some sick elderly persons in the US, especially among those confined to institutions, become vitamin D deficient. For several reasons, the vitamin D requirement increases with age, and a total supply of 15 to 20 micrograms/day (600 to 800 IU) from all sources is recommended. Special attention should be paid to persons most likely to need supplementation, such as the housebound, persons with malabsorption, and persons with interruption of the enterohepatic circulation. Osteomalacia, the bone disease produced by severe vitamin D deficiency, is less common in the US than in Europe, but subclinical vitamin D deficiency may contribute to the pathogenesis of hip fractures, both through increased liability to fall and through PTH-mediated bone loss. The extent to which vitamin D deficiency contributes to hip fractures in the US is unknown, and is an important area for future research. Excess intake of vitamin D or of its metabolites may result in hypercalcemia and extra-osseous calcification, particularly in arterial walls and in the kidney, leading to chronic renal failure. The dose of vitamin D that causes significant hypercalcemia is highly variable between individuals but is rarely less than 1000 micrograms/day. Smaller doses can cause hypercalciuria and nephrolithiasis and possibly impaired renal function. Vitamin D administration may raise plasma cholesterol but there is no convincing evidence that the risk of myocardial infarction is increased. The recommended total supply for the elderly of 20 micrograms/day is most unlikely to be harmful, except in patients with sarcoidosis or renal calculi.

Factors Associated with Cortical and Trabecular Bone Loss as Quantified by Peripheral Computed Tomography (pQCT) at the Ultradistal Radius in Aging Women

“…Data have indeed provided evidence that local factors may be of prime importance in transducing mechanical signals into a coordinated osteogenic response [34][35][36]. Similarly, serum PTH (1-84) was found to be significantly related to cortical but not to trabecular density, supporting previous reports indicating that cortical bone is more susceptible to bone loss caused by secondary hyperparathyroidism [37,38].…”

“…The differences in both parameters over the age range were equivalent to reductions of −0.41% and −0.65%, respectively, consistent with a continuing loss of skeletal integrity throughout life at the cortical and trabecular level. It has been postulated that enhanced PTH secretion, secondary to compromised vitamin D status or metabolism, may induce or exacerbate bone loss in older individuals [27][28][29]. Moreover, interventional data have confirmed the role of vitamin D deficiency in the pathogenesis of agerelated osteoporosis and indicated the need to maintain serum cholecalciferol levels within the normal range in elderly people [30].…”

Effect of vitamin D supplementation on vitamin D status and bone turnover markers in young adults

“…Laboratory results for baseline and post supplementation measurements for both groups are presented in Table 2. At baseline, one subject was vitamin D deficient according to the cutoff level of o25 nmol/l (Parfitt et al, 1982; Department of Health, 1998), whereas no subjects were deficient post supplementation. A level of 30 nmol/l has also been suggested as the cutoff for vitamin D deficiency (Lips et al, 1988).…”

High prevalence of vitamin D insufficiency in healthy elderly people living at home in Argentina

“…Different categories have been proposed to classify vitamin D status: vitamin D deficiency that leads to osteomalacia, with the ensuing histomorphometric changes (Parfitt et al, 1982), vitamin D insufficiency that has an effect on calcium homeostasis, such as a diminution in calcium absorption and 1,25(OH)2D levels, leading to secondary hyperparathyroidism (Peacock et al, 1985), and vitamin D sufficiency with no effect on calcium homeostasis. The threshold of serum 25OHD that separates vitamin D sufficiency from insufficiency is generally defined by its biological effect, primarily by the increase in serum parathormone.…”