With adequate vitamin D extra calcium unnecessary

New research says that in order to maintain calcium metabolism, taking as much as 800 milligrams of calcium daily is probably unnecessary provided that vitamin D levels are normal.

It is well known that vitamin D is essential for healthy teeth and bones, and it helps the body absorb and use calcium, but until now the ideal daily intake of vitamin D has been unclear.

In a new study senior author Dr. Gunnar Sigurdsson, from Landspitali-University Hospital in Reykjavik, Iceland, and colleagues assessed calcium intake and serum vitamin D levels in connection to the 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.

A lack of vitamin D or calcium is usually associated with an increase in PTH, but how important each nutrient is to this process has not been previously questioned.

In their study, Sigurdsson and colleagues noticed that when vitamin D levels were low maintaining calcium intake above 800 mg/d seems to help normalize calcium metabolism, according to the PTH level.

But when there were higher vitamin D levels, there appeared to be no benefit for achieving calcium intake above 800 mg/d.

The authors say the study suggests that vitamin D sufficiency may be more important than high calcium intake in maintaining desired values of serum PTH and Vitamin D may have a calcium-sparing effect.

They say 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.

The study is published in the Journal of the American Medical Association November 9, 2005.