The first clinical trial to track calcium's effects on bone density in girls aged 8-13 for as long as seven years has found that calcium supplementation significantly increased bone mass development during a critical childhood growth spurt.
The findings suggest that elevated calcium use by pre-adolescent girls is likely to help prevent fractures and osteoporosis much later in life.
"Because most bone mass is accumulated during this phase of growth, pre-adolescence may represent the time of highest need for calcium in a female's lifetime," said Velimir Matkovic, lead author of the study, based at Ohio State University.
Matkovic pioneered research on the concept of calcium's relationship to peak bone mass in the 1970s, when he documented differing fracture rates among populations that consumed contrasting levels of dairy products over their lifetime.
In the new research, published in the January issues of the American Journal of Clinical Nutrition and the Journal of Nutrition, the seven-year length of the study allowed researchers to determine that calcium supplementation has the most significant effect on girls' bone build-up during the pubertal growth spurt.
The pubertal growth spurt accounts for about 37 per cent of the gain in the entire adult skeletal mass, meaning "inadequate calcium intake during this period compromises the bone mineral accumulation rate," Matkovic said.
The researchers also found that over time, after the onset of menstruation, calcium supplementation's effects on bone density decreased.
The calcium-supplemented group among the 354 girls in the trial showed a faster rate of bone mass development from the beginning of the study. The biggest difference in bone mineral density between the supplemented and non-supplemented groups of girls occurred from between one year before and one year after the onset of menstruation.
By young adulthood, significant effects remained at the metacarpals in the hands, the forearm and the hip.
The average dietary calcium intake among all study participants was 830 milligrams per day. The supplemented group took in an average of an additional 670 milligrams per day, equivalent to the calcium found in about 18 ounces of milk.
The researchers also noted that the calcium requirement for growth is body-size specific; taller individuals need more calcium during growth than shorter individuals.
"The importance of preventing osteoporosis can't be overstated," Matkovic said. "Prevention of this disease will not only improve the population's quality of life, but will also undoubtedly save on the skyrocketing health care costs associated with treatment."