Supplements of calcium and vitamin D may boost the bone health of girls undergoing puberty, and potentially reduce the risk of osteoporosis later in life, suggests a new study from Down Under.
Australian researchers reporting in Osteoporosis International, showed that a supplement containing 800 mg of calcium and 400 IU of vitamin D3 produced significant increases in the bone density and strength of peripubertal female identical twins, compared with placebo.
The study is published in the journal Osteoporosis International.
Osteoporosis is characterized by low bone mass, which leads to an increase risk of fractures, especially the hips, spine and wrists. An estimated 75 million people suffer from osteoporosis in Europe, the USA and Japan.
Women are four times more likely to develop osteoporosis than men.
Potential reduction of osteoporosis has traditionally been a two-pronged approach by either attempting to boost bone density in high-risk post-menopausal women by improved diet or supplements, or by maximising the build up of bone during the highly important pubescent years.
About 35 per cent of a mature adult's peak bone mass is built-up during puberty.
Researchers from the Australian Catholic University recruited 20 pairs of identical twins and randomly assigned one from each set of twins to receive the vitamin D, calcium combination, and the other to receive a placebo for six months.
The study, reportedly the first to use peripheral quantitative computed tomography (pQCT) to measure bone responses to the combined supplement in peripubertal children, found that the vitamin D and calcium combination was associated with increased bone density and bone strength in the shinbone (tibia) and in the arm (radius).
Indeed, shin and arm bone strength was improved by between 4 and 66 percent, depending on the specific site of the bone tested.
Strong supporting science
The study supports previous findings, including results from an 18-month randomised trial from scientists at the University of Sheffield in the UK (American Journal of Clinical Nutrition, February 2008, Vol 87, Pages 455-462).
In the Sheffield study, a daily 792 mg calcium supplement was associated with increases in bone mineral content and density. However, the effects were then reversed once supplementation was discontinued.
Commenting on the mechanism, the Sheffield scientists proposed that the mineral most likely worked by suppressing bone turnover.
Other reports have linked calcium and vitamin D with protection against colon cancer. Now, study findings suggest that calcium and vitamin D act together to achieve this effect.
Although calcium and vitamin D collaborate in bone growth, it was unclear if they work together to prevent the colon polyps that lead to cancer. In the new study, Dr. Maria V. Grau, from Dartmouth Medical School in Lebanon, New Hampshire, and colleagues assessed the effects of calcium use and vitamin D levels on polyp formation in 803 subjects who've had such polyps before.
At low levels of vitamin D, calcium use had no effect on polyp formation, the researchers note. At higher levels, however, calcium use was associated with a 29 percent reduction in the risk of polyp recurrence.
Conversely, the authors found that vitamin D levels only had an effect on recurrence when subjects used calcium supplements. Among calcium users, the risk of recurrence fell as vitamin D levels increased.
Further studies are needed to uncover the mechanisms underlying the interaction between vitamin D and calcium, the authors state. "Nevertheless, these data clearly suggest the potential for important (preventive) effects from calcium and vitamin D."
The findings were presented in the Journal of the National Cancer Institute.