Adolescent girls who take calcium supplements may increase their total body bone mineral density (BMD), an effect that is sustained over time during puberty, according to two reports in the American Journal of Clinical Nutrition. These findings may have implications for the prevention of fractures during growth and osteoporosis later in life.

Dr. Sophia Ish-Shalom, at Rambam Medical Center in Haifa, Israel, and colleagues, previously showed that calcium supplementation (1000 mg calcium carbonate per day) for 1 year enhanced bone mineral density in menstruating adolescent girls. In the current study, the researchers followed these girls for 3.5 years after they stopped taking calcium supplements.

Included were 49 girls who had taken the supplements and 47 girls who had taken a placebo. The average subject age at the beginning of the study was 14 years.

Total body BMD accumulation tended to be higher in the calcium-supplemented group. Statistically significant differences were observed in subjects who took at least 75 percent of the prescribed calcium supplements.

Calcium supplementation and time since inclusion in the initial study were significant predictors of increased total body BMD.

“Our research tends to support the idea that calcium supplementation may provide a sustained effect on BMD and positively influence bone accretion during growth,” Ish-Shalom’s group suggests.

In the second study, Dr. Velimir Matkovic at Ohio State University in Columbus and colleagues, randomly assigned girls to calcium supplements 1000 mg per day or placebo. The average age at the start of the trial was about 11 years old.

One hundred twenty-three subjects in the placebo group and 103 in the calcium group completed 4 years of the study; 100 in the placebo group and 79 in the calcium group completed 7 years of the study.

After 4 years, the authors observed “highly significant treatment effects” on total body BMD, but the effects diminished thereafter.

Because calcium requirements may vary from one ethnic group to another, the authors recommend that “each country should develop its own standards that are specific to the people living in the region.”

Matkovic’s group also found that 20 girls in the placebo group and 9 in the calcium group had a bone fracture due to moderate trauma, which occurred an average of 1.2 years after menstruation began, suggesting that growth rate may also be a relevant factor in setting standards for dietary calcium intake.

“The results of this study may be important for the prevention of bone fragility fractures during growth, as well as for the primary prevention of osteoporosis,” they conclude.

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SOURCE: American Journal of Clinical Nutrition, January 2005.

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