Lee Swanson Research Update

Serum Vitamin D Is Essential For Calcium Metabolism

March 2006

vitamin D

According to the results of a recent study, serum vitamin D status is more important than calcium intake for calcium metabolism, which is necessary for maintaining bone health. Insufficient levels of serum vitamin D may result in higher blood levels of parathyroid hormone (PTH), which, in turn, may remove calcium from bones. Thus, it may be necessary for patients to consume more than 800 mg per day of the mineral to maintain bone health, the researchers say.

For this study, 2,320 healthy adults in Iceland were divided into three age groups: 30-45; 50-65; and 70-85. The subjects responded to a semiquantitative food-frequency questionnaire that assessed their vitamin D and calcium intakes. A total of 944 subjects completed the questionnaire.

The subjects were then divided again into subgroups based on calcium consumption and serum vitamin D (measured as serum 25-hydroxyvitamin D) levels. The calcium consumption groups were: less than 800 mg per day; 800-1,200 mg per day; or more than 1,200 mg per day. The serum vitamin D groups were: less than 10 ng/mL; 10-18 ng/mL; or more than 18 ng/mL.

Serum PTH was lowest in the group that had more than 18 ng/mL of serum 25-hydroxyvitamin D and highest in the group with less than 18 ng/mL of the vitamin. In the first group, consumption of less than 800 mg per day of calcium was associated with higher serum PTH versus intake of more than 1,200 mg per day of the mineral.

Serum 25-hydroxyvitamin D sufficiency was able to produce ideal PTH levels whereas even high calcium intake failed to produce the same effect when vitamin D status was low.

Journal of the American Medical Association 294(18):2336-2341, 2005

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