Calcium has long been touted as a major factor in bone health and the fight against osteoporosis. But now researchers at Creighton University in the US appear to have shown that calcium may not be the only factor when it comes to healthy bones - in fact, it is much more effective when used with another nutrient, phosphorous.
Dr Robert P. Heaney was the lead author of the study, whose findings were presented at the National Osteoporosis Foundation's Fifth International Symposium earlier this month.
"The best way to help our patients meet their needs is to use a source that provides both calcium and phosphorus, such as dairy products and/or a calcium phosphate supplement," said Dr Heaney. "Women undergoing treatment for osteoporosis today typically are taking calcium supplements in amounts providing 1,000 to 1,500 mg of calcium per day. Data shows that, in addition to providing the extra calcium a patient usually needs to slow bone loss or to support treatment-induced bone gain, this amount of calcium can bind up to 500 mg of phosphorus."
He continued: "Although this would present no serious problem for many people, it could impact women over 60 years of age who have diets that contain less than the National Academy of Sciences recommended daily allowance of 700 mg of phosphorus. For these women, the usual calcium supplement, calcium carbonate, may block most of the absorption of phosphorus. If this happens, the calcium won't do much good because bone mineral consists of both calcium and phosphorus."
Dr Heaney's study of the co-dependence of calcium and phosphorus on growth and bone development could affect the formulation of many multi-vitamin and calcium supplement products available to consumers. The popularity of calcium supplements and calcium-fortified foods and beverages has reached record levels in recent years, since a 1984 conference on osteoporosis raised public awareness of the importance of calcium in bone development and recommended new, higher consumption levels for adults.
Since phosphate makes up more than half the mass of bone mineral, the researchers said that diet must contain sufficient phosphorus if bone is to be built or rebuilt. Phosphorus inadequacy may be more prevalent than commonly believed, at least partly as a result of changes in diet (e.g., strict vegetarianism) and weight reduction programmes.
Phosphorus supplements are not widely used in the US, Dr Heaney said. Calcium phosphates have been widely used in analgesics and other pharmaceutical products for many years because of their excipient properties - they allow medications to be formed into specific shapes and help make them consistent, and may also work as the vehicle for the drug. The researchers hope that their study may lead to the value of calcium phosphates in nutritional and dietary supplements becoming more widely recognised and more widely used.
The research was sponsored by the pharmaceutical company Rhodia, a major producer of calcium supplements.