BoneKEy-Osteovision | Perspective
Adolescence: How do we increase intestinal calcium absorption to allow for bone mineral mass accumulation?
Steven A Abrams
Gordon J Strewler
An increase in calcium absorptive efficiency (fractional absorption of dietary calcium) during adolescence is associated with a rapid increase in total body bone mineral mass (BMM) accumulation. This increase occurs across a range of calcium intakes. It appears to be principally mediated by hormonal changes of puberty including increases in insulin-like growth factor-1 (IGF-1), luteinizing hormone (LH) and estrogen. Calcium supplementation during adolescence has led to short-term increases in measures of BMM, but has not had a consistent long-term benefit. This is likely due to the efficient nature of catch-up of mineralization throughout adolescence and early adulthood as long as calcium intake is not severely deficient and other dietary factors are adequate. Vitamin D is needed for active (transcellular) calcium absorption of calcium. However, in contrast to adults, no close relationship between serum 25-hydroxyvitamin D (25-OHD) concentration and calcium absorption in non-vitamin D-deficient adolescents has been demonstrated. No data are available to identify an optimal 25-OHD concentration in adolescents, although avoidance of very low levels is necessary. The routine supplementation of adolescents with high dose vitamin D (e.g., more than about 400 IU/d) is not justified based on currently available data unless specific risk factors for low vitamin D status or malabsorption of vitamin D exist. Other interventions that may enhance the absorption of calcium require further evaluation but may be of importance. For example, prebiotics have been demonstrated to enhance calcium absorption and BMM acquisition, but longer-term studies are needed. For most adolescents, a combination of avoiding a very low calcium intake (< 600-800 mg/d), and maintaining a diet with adequate amounts of other essential bone nutrients will lead to adequate calcium absorption and BMM accumulation during adolescence. Revision of dietary guidelines for calcium and vitamin D to create a full range of recommendations is urgently needed.
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