Extra calcium unnecessary with adequate vitamin D (Reuters)

NEW YORK (Reuters Health) - For maintaining calcium metabolism, intake of calcium levels above 800 milligrams daily is probably unnecessary provided that vitamin D status is adequate, according to a report in the Journal of the American Medical Association this week.

Vitamin D is essential to healthy teeth and bones, and it helps the body absorb and use calcium, but the ideal intake of vitamin D has been unclear, senior author Dr. Gunnar Sigurdsson, from Landspitali-University Hospital in Reykjavik, Iceland, and colleagues note.

The researchers assessed calcium intake and serum vitamin D levels with respect to optimal parathyroid hormone (PTH) levels in 944 healthy Icelandic adults. PTH is a major hormone maintaining normal serum concentrations of calcium and phosphate and is itself regulated through levels of calcium. An insufficiency of vitamin D or calcium is generally associated with an increase in PTH, but the relative importance of each nutrient to this process has not been addressed.

In their study, Sigurdsson and colleagues noticed that in the presence of low vitamin D levels, maintaining calcium intake above 800 mg/d seems to help normalize calcium metabolism, as determined by the PTH level.

By contrast, in the presence of higher vitamin D levels, there appears to be no benefit for achieving calcium intake above 800 mg/d.

"Our study suggests that vitamin D sufficiency may be more important than high calcium intake in maintaining desired values of serum PTH," the authors conclude. "Vitamin D may have a calcium-sparing effect and as long as vitamin D status is ensured, calcium intake levels of more than 800 mg/d may be unnecessary for maintaining calcium metabolism."

The report also indicates that vitamin D supplements are needed to achieve an adequate status for people living in northern climates.

SOURCE: Journal of the American Medical Association November 9, 2005.