The results, presented yesterday at the 53rd annual Orthopaedic Research Society meeting in San Diego, were obtained from a randomized, double-blind study with 5,201 female U.S. Navy recruits during eight weeks of basic training.
"What really surprised us is that calcium/vitamin D supplements made a significant difference in such a short period of time. Frankly, we were not sure we would see any statistically significant results in only eight weeks," said lead researcher Joan Lappe from Creighton University in Omaha.
The combination of vitamin D and calcium has long been recommended to reduce the risk of bone fracture for older people, particularly those at risk of or suffering from osteoporosis, which is estimated to affect about 75m people in Europe, USA and Japan.
The action of the nutrients is complimentary, with calcium supporting bone formation and repair, while vitamin D helps the body absorb calcium.
The new study, funded by the U.S. Department of Defense, appears to suggest that daily supplements of the vitamin and mineral may also provide benefits for those engaged in athletic training.
Stress factures are said to be one of the most common and debilitating overuse injuries seen in U.S. military recruits with 21 per cent of female recruits reported to suffer from this form of injury. Male recruits suffer less.The research of Professor Lappe, presented to attendees in San Diego, divided the recruits into two groups - one group received a daily supplement of 2,000 Mg of calcium and 800 IU of vitamin D, and the other group received a placebo.
At the end of the eight weeks of basic training, 170 women in the placebo group experienced stress fractures; 25 per cent more women than in the calcium/vitamin D supplemented group. NutraIngredients.com has not seen the full data.
"It appears that supplementation with calcium and vitamin D provides a health-promoting, easy and inexpensive intervention that does not interfere with training goals," said Lappe.
Further studies are needed to confirm these findings, but the results appear to fit with numerous other studies linking the nutrients to improved bone health.
The current EU recommended daily intake of calcium is 800mg, with an upper safe limit of 2500mg. Vitamin D has a RDI of 400 IU, although campaigners are calling for an increase to 1000 IU, half the upper safe limit recommended by the EU and US.
In the US, the DRI (dietary reference intake) for calcium is 1000mg for adults aged 19 to 50, and 1200mg from 51 to 70. For vitamin D it is five micrograms per day, rising to 10 after the age of 50.