PEDIATRICS Vol. 115 No. 3 March 2005, pp. 792-794 (doi:10.1542/10.1542/peds.2004-2199)
COMMENTARY |
Bone Health: It’s More Than Calcium Intake
Department of Pediatrics
University of Wisconsin Medical School
Madison, WI 53715
The National Academy of Sciences has recommended that adequate dietary intake of calcium is necessary in children and adolescents for the development of peak bone mass and prevention of fractures and osteoporosis later in life.1 The current recommended adequate intake for children 9 to 18 years of age is 1300 mg/day, which is higher than that in other developed countries.2 This recommended intake is based largely on the results of calcium-balance studies that show that in healthy children of this age, maximal net calcium balance is achieved with this intake.3,4 At higher levels of intake, additional calcium is mostly excreted. Peak calcium accretion is attained at the ages of 12.5 years in girls and 14.0 years in boys.3 Despite this, the percent of children achieving the recommended adequate calcium intake in the United States declines dramatically after the second year of life, reaching its nadir between 12 and 19 years of age, when documented intakes in this age group approximate only 700 to 1000 mg/day.1,5–7 In fact, only 10% of adolescent girls achieve the recommended adequate dietary intake of calcium. The article by Lanou et al2 in this issue, on careful review of the evidence, concludes that, by using measures of bone health (fracture rate and radiologic measures of bone mineralization and bone strength) rather than calcium-balance studies, an intake of 1300 mg/day is not warranted. Because the largest dietary source of calcium in the United States is dairy products (72%),8 these authors also maintain that increased consumption of dairy products, as currently promoted by industry and federal nutrition guidelines, is not indicated.
Lanou et al also point out that, by using radiologic measures of bone health, physical activity is the most important modifiable factor that determines increased bone growth and development in adolescents.2 This was confirmed recently by a 10-year longitudinal study in adolescents by the Penn State Young Woman’s Health Study.9 In 80 women who were followed from 12 to 22 years of age with an average daily calcium intake of 1058 ± 440 mg/day (range: 480–1958 mg/day), only exercise history (participation in sports), rather than calcium intake, was significantly correlated with bone mineral density and bone strength. It is well known that weight-bearing exercise plays a role in achieving maximal peak bone mass, but data to quantify the effect are limited. It is unclear, however, whether any given level of calcium intake influences the degree of benefit derived from exercise on bone mass or whether exercise alone, independent of calcium intake, improves bone mass. Although one could speculate that less-active people need more calcium in their diets than active ones, the Penn State study found no interaction between calcium intake and physical activity.9 This is in contrast to another recent report from the United Kingdom. In this cross-sectional study of 38 girls and 38 boys between 8 and 11 years of age, there was a synergistic effect on bone density of a calcium intake of 700 to 800 mg/day and vigorous exercise (25–40 minutes per day).10
Getting to the bottom line, I agree with Lanou et al that there is no direct evidence that calcium supplements at any level in childhood or adolescent have any impact on long-term bone health in adults, including osteoporosis. Even when using radiologic measures of bone health rather than calcium-balance studies, it is difficult to show a positive effect of calcium intake alone on bone mineral over the short term, let alone long-term benefits; however, I do agree with the National Academy of Sciences that the immediate goal of pediatric health care providers is still to achieve maximum peak bone mass in our adolescent patients. What is the best way to achieve this goal? A calcium intake of 1300 mg/day will cause no harm that we know of, and the National Academy of Sciences has set an upper limit of 2500 mg/day for this age group. The easiest way to achieve this level of intake is to consume dairy products. In light of our ongoing concerns about pediatric obesity, low-fat dairy products would be preferred. In addition, with dairy products, many other beneficial nutrients will be supplied to our patients including vitamin D, generally not available from other dietary sources. It is interesting to note that longitudinal calcium intake has recently been negatively correlated with percent body fat in children.11,12 Pediatric care providers should continue to promote physical activity and optimal calcium intake in childhood and adolescence, with the anticipation that if these healthy lifestyle practices are instituted early in childhood, they will continue throughout a lifetime.
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FOOTNOTES |
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Accepted Oct 14, 2004.
Address correspondence to Frank R. Greer, MD, Wisconsin Perinatal Center, Meriter Hospital, 202 S Park St, Madison, WI 53715. E-mail: frgreer{at}wisc.edu
Conflict of interest: Dr Greer serves as the representative of the American Academy of Pediatrics on the 3-A-Day of Dairy for Stronger Bones Advisory Panel to the National Dairy Council. Dr Greer receives reimbursement for travel expenses from the National Dairy Council for his service.
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REFERENCES |
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- Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. Washington, DC: National Academy Press; 1997
- Lanou AJ, Berkow SE, Barnard ND. Calcium, dairy products, and bone health in children and young adults: a reevaluation of the evidence.
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[Abstract/Free Full Text] - Baily DA, Martin AD, McKay HA, Whiting S, Mirwald R. Calcium accretion in girls and boys during puberty: a longitudinal analysis. J Bone Miner Res. 2000;15 :2245 –2250[CrossRef][Web of Science][Medline]
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- National Institutes of Health Consensus Conference. NIH consensus developmental panel on optimal calcium intake.
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[Abstract/Free Full Text] - Carruth BR, Skinner JD. The role of dietary calcium and other nutrients in moderating body fat in preschool children. Int J Obes. 2001;25 :559 –566
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PEDIATRICS (ISSN 1098-4275). ©2005 by the American Academy of Pediatrics
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