Calcium supplements may have usefulness limit, suggests study
young women after a certain threshold level of intake has been
achieved, according to a new study from Creighton University.
In the United States, the recommended daily intake of calcium for women aged between 18 and 50 years is 1000mg. Calcium, together with vitamin D which is understood to help absorption, is crucial for maintaining strong bones and helping to prevent the brittle bone disease osteoporosis in later life.
Between the ages of 9 to 18 years, crucial years for building bone density, girls are advised to consume 1,300 mg per day. After the age of 50, when osteoporosis is most prolific, 1,200mg per day is recommended.
The World Health Organisation regards osteoporosis as an important health concern, since one in three women and one in seven men will experience a fracture due to osteoporosis at some point after the age of 50. In Europe, osteoporosis causes around 1.1 million fractures each year.
The Creighton researchers sought to test the hypothesis that increasing calcium intake in post-adolescent women increases skeletal consolidation.
They recruited 152 healthy young women aged between 20 and 25 years, who had a body mass index of between 19.5 and 25.5. Food diaries kept for seven days ascertained that all the participants had a low dietary intake of calcium, of between 424 and 786 mg/d. They were randomly assigned to two groups: one took 500mg of calcium carbonate supplements three times a day, and the other took a placebo. Both groups also took a daily multivitamin.
Their bone density was measured every six months. All of the 121 participants who remained in the study after 12 months, regardless of whether they received the calcium or the placebo, displayed a "modest but significant" increase in bone mineral content for total body, total hip and lumbar spine, and in lumbar spine bone mineral density. No change in total hip bone mineral density with observed.
The researchers wrote in the October issue of the Journal of Nutrition: "Calcium supplementation did not have any measurable effect on bone mass accrual."
However they noted that both groups upped their usual dietary intake of calcium over the course of the study by around 15 percent. The researchers said that the combined effect of this and the multivitamins meant even the control group ended up with a daily intake of 800mg of calcium per day, which they hold may be near the threshold at which additional calcium stops having an effect on bone accrual.
