Exercise and high levels of vitamin D intake during this period of life are also critical for building bone mass that will survive into old age, researchers told the International Osteoporosis Foundation (IOF)conference in Rio de Janeiro.
Researchers from the University of Geneva in Switzerland raised the possibility that calcium supplementation in prepubertal girls could hasten the arrival of the first menstrual period. But girls who begin menstruation earlier will build a higher 'peak' bone mass by young adulthood, possibly protecting themselves against osteoporosis later in life.
Osteoporosis is second only to cardiovascular disease as a leading health care problem, according to the World Health Organisation. Worldwide, the lifetime risk for a woman to have an osteoporotic fracture is 30-40 per cent, yet in seven major countries - France, Germany, Italy, the United States, the United Kingdom, Spain and Japan - less than half of women with osteoporosis are diagnosed, according to the IOF.
In the next 50 years, the number of hip fractures for both men and women will more than double. This means the need for prevention is more urgent than ever.
"Peak bone mass, which helps determine osteoporosis risk, is influenced by genetic, hormonal, and environmental factors," Geneva researcher Dr Thierry Chevalley told those attending the recent conference in Brazil. "Nutrition, especially calcium and protein, and physical activity, are important determinants of osteoporosis risk."
For almost a decade, Chevalley and his colleagues have been following bone development in a group of 144 Swiss girls who were given either calcium supplements or a placebo for a year at the age of eight. The goal of the research is to understand whether bone mass gained as a result of this supplementation will raise the 'peak' bone mass that is reached in young adulthood.
Chevalley's team have already found a significant some significant results (conference abstract OC27), namely that the earlier girls underwent menarche, their first menstrual period, the more bone mass they had accumulated by age 16.5.
"This is consistent with earlier data showing that late menarche and low calcium intake during childhood are risk factors for developing osteoporosis," he said.
The researchers also found that the 67 girls remaining in the study who had received calcium supplementation at age eight had experienced earlier menarche than the 58 girls remaining in the placebo group. Menarche occurred, on average, six months earlier in the calcium-supplemented group.
Chevalley noted that it is premature to conclude that the early calcium supplementation and menarche will provide these girls with higher peak bone mass in adulthood.
"We need to follow this cohort until they attain their full peak bone mass," he said. "But the current findings should encourage further research about the interaction between nutrition and endocrine factors on bone mass acquisition from puberty to the end of the growth period."
In the same session, Dr Marjo Lehtonen-Veromaa of the University of Turku in Finland reported that girls who engage regularly in athletics build more bone mass than nonathletic girls (conference abstract OC25).
The researchers also found that that reduced vitamin D levels were associated with lower levels of bone mineral density in portions of the spine.
There is increasing evidence of major vitamin D deficiency among Western populations, thought to be a partial result of increased protection of the skin from the sun, the body's main source of production.
Studies have previously demonstrated however that supplementation with the vitamin, given alone or in combination with calcium, can reverse this deficiency to prevent bone loss and improve bone density in the elderly.