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[Show abstract][Hide abstract] ABSTRACT: Vitamin D deficiency and insufficiency are widespread among the population, especially in risk groups such as young children,
pregnant women, older persons, in particular the homebound and institutionalized, and nonwestern immigrants.1–3 Consequences are mineralization defects, resulting in rickets or osteomalacia, and secondary hyperparathyroidism resulting
in osteoporosis and fractures. Many studies have been done in older persons, but data from the general adult population are
lacking. Vitamin D deficiency and insufficiency can be prevented and the potential gain is high. This paper starts with the
pathophysiological background and the data coming from molecular biology, in particular the knock-out models. Subsequently,
mineralization disorders, as well as risk factors, are discussed. This is followed by the relationship between vitamin D deficiency,
osteoporosis, and fractures. The pathophysiology and the prevention of bone loss and fractures will be discussed. Subsequently
the implications for public health, vitamin D requirement, and the use of supplements will be discussed.
[Show abstract][Hide abstract] ABSTRACT: During growth, bone strength, defined as the ability to resist fracture, develops through the adaptation of skeletal mass
and geometry in response to mechanical loads. Bones have a tremendous potential to respond to mechanical loading by changing
shape, and this adaptive ability is much greater during growth than after growth ceases. Throughout childhood and adolescence,
the skeleton is adapting to changes in mechanical loads to become strong enough to support body weight and current physical
activity. Furthermore, at the completion of growth, the bones must be of sufficient strength to meet the lifetime load-bearing
demands of adulthood. Bone mass, size, and strength are regulated by daily mechanical loads, but the relative response to
loads is dependent upon other factors: genetics, lifestyle choices, and health, hormonal and nutritional status. This chapter
focuses on the role of mechanical loading (physical activity) and calcium nutrition in childhood skeletal development.
[Show abstract][Hide abstract] ABSTRACT: The purpose of this study is to evaluate the effects of calcium supplementation at different levels on bone mineral accretion
and body composition in Chinese adolescents with low habitual calcium intakes. A double-blind randomized controlled trial
(RCT) of four doses of calcium supplementation given for 24 months to 257 (135 boys and 122 girls) healthy adolescents aged
12-15 years. The subjects were randomly assigned to four groups, each group receiving chewable calcium carbonate tablets providing
elemental calcium at 63, 354, 660, or 966 mg/d, respectively. Bone mineral content (BMC) and bone mineral density (BMD) of
the total body, lumbar spine and body composition were measured with dual-energy X-ray absorptionmetry. Information on dietary
intakes and physical activity were collected with questionnaires. Subjects were re-classified as three groups by actual total
calcium intakes while average total calcium intakes in each group were 386, 629 and 984 mg/d. After supplementation, BMC of
total body in Group two (2464g) and Group three (2437g) were significant higher than that in Group one (2321g) in males. Similar
significant differences in lean body mass and body weight (P<0.05) were also found in males. However, there were no significant
differences among groups in females. Gender, puberty development, physical activity and calcium intakes played a significant
role in BMC retention at total body in adolescents (Rc2=0.429). In conclusion, calcium supplementation more than 250 mg/d
lasting for two years improves growth of BMC, lean body mass and weight in Chinese male adolescents with low habitual calcium
intakes. Gender, tanner stage, physical activity and calcium intakes are the most important factors on BMC retention.