Start Young to Build Strong Bones

Healthnotes Newswire (April 28, 2005)- By supplementing with calcium at an early age, girls may be able to prevent bone loss later in life that can lead to osteoporosis, according to the Journal of Clinical Endocrinology and Metabolism (2004; 89:4916-22).

Osteoporosis, or thinning of the bones, may cause significant disability in older people. As bone mass is lost, the skeleton becomes increasingly fragile and susceptible to fractures after minimal trauma. The wrist, hip, and spine are common sites for osteoporotic fractures to occur. White and Asian women, and people who smoke, abuse alcohol, are underweight, have low calcium and vitamin D intake, or have a family history of osteoporosis are at an increased risk for developing the disease.

Strategies for osteoporosis prevention focus on maximizing and maintaining bone mass. Bone mass tends to peak around age 30, followed by a decline in bone density that accelerates after menopause.

About 50% of the total adult bone mass is gained during childhood and adolescence. Providing the body with the nutrients necessary for optimal skeletal formation is especially important during these periods of rapid growth. As calcium is one of the major minerals comprising bone tissue, it has been studied for its effects on bone growth in children.

Bone density in children appears to increase in response to calcium supplementation; however, the effect of calcium supplementation on girls at different stages of puberty is less clear. To investigate this relationship, 51 pairs of twin girls (average age ten years) completed a two-year study. One member of each twin pair was assigned to receive 1,200 mg of calcium (as calcium carbonate) per day and the other twin received a placebo. At the beginning of the study and after 6, 12, 18, and 24 months, bone density measurements at the wrist, lower spine, and hip were taken, and total body bone mineral content was assessed. Total calcium intake from diet and supplements was also estimated. Members of each twin pair were then directly compared.

Members of the twin pair who received supplemental calcium had an average total daily intake of 1,600 mg of calcium, while those receiving the placebo consumed an average of 700 mg per day. The average total daily calcium intake was lower than expected in the calcium-supplemented group because the participants did not take their supplement every day. After 12 months, the calcium-supplemented twins had gained significantly more bone mass at the hip and lower spine, and had significantly higher total body bone mineral content than did the twins taking the placebo. Total body bone mineral content continued to increase until 24 months among the twins taking calcium; however, bone densities at individual sites did not differ significantly between the girls at this time. The authors suggest that skeletal growth may have accelerated at this point, so that the amount of supplemental calcium was not sufficient to meet the increased need. There was no difference in bone density at the wrist within the twin pairs.

The results of this study suggest that supplementing with calcium during late childhood/early adolescence may increase measures of bone density, possibly preventing the later development of osteoporosis. Other recent studies have also suggested that calcium supplementation in girls who are near the onset of puberty might have a lasting benefit on bone density.