Adults may need half the amount of daily calcium currently recommended, researchers report based on a review of published studies.
"Our meta-analysis did not support a dose-response relationship between a higher calcium intake beyond 555 milligrams per day and the risk for hip fracture," Professor Heike Bischoff-Ferrari, of University Hospital Zurich, Switzerland, told Reuters Health.
This is in contrast to current guidelines that recommend between 1 200 to 1 500 milligrams of calcium per day among older adults, the researcher noted.
The results are based on combined data from forward-looking studies involving nearly 180 000 women and about 68 600 men, aged 41 years and older.
Moreover, when the investigators combined data from randomised controlled trials involving over 5 600 mostly postmenopausal women aged 58 years and older, they found that calcium supplementation may increase the risk for hip fracture by 64 percent.
Previous studies have not clearly identified the optimal daily calcium intake, the researchers report in a report in the American Journal of Clinical Nutrition.
Other factors involved
They suggest that other dietary deficiencies, involving phosphate and vitamin D, appear to affect calcium absorption and, in turn, influence bone health.
Earlier studies documented that calcium supplements (citrate and carbonate) may reduce the phosphate absorption needed to build calcium into bone, Bischoff-Ferrari said. The combined effect may enhance bone loss, especially among frail older individuals.
"Furthermore, calcium absorption is enhanced significantly with better vitamin D status," Bischoff-Ferrari added. "Vitamin D in a dose of 800 international units per day, with or without calcium, has been shown to reduce both falls and fractures among adherent older individuals."
The investigators say studies are needed to determine the optimal combination of vitamin D and calcium among older individuals. "It may well be that current recommendations are too low for vitamin D, and too high for calcium," Bischoff-Ferrari said.
SOURCE: American Journal of Clinical Nutrition, December 2007. – (Reuters Health)