TUESDAY, Nov. 8 (HealthDay News) -- Vitamin D intake is crucial to maintain healthy calcium metabolism and may make intake of more than 800 mg/d of calcium unnecessary, according to a study in the Nov. 9 issue of the Journal of the American Medical Association.
Laufey Steingrimsdottir, Ph.D., of the Public Health Institute of Iceland, and colleagues conducted a study of 2,310 healthy Icelandic adults to ascertain the relative importance of high calcium intake and serum 25-hydroxyvitamin D for calcium homeostasis, which was determined by serum intact parathyroid hormone (PTH) levels. A total of 994 participants completed all parts of the study.
The study population was divided into three groups by age (30-45, 50-65 and 70-85 years) and then divided again into groups according to calcium intake (less than 800 mg/d, 800-1,200 mg/d, and more than 1,200 mg/d) and serum 25-hydroxyvitamin D level (less than 10 ng/mL, 10-18 ng/mL, and more than 18 ng/mL).
Overall, PTH level seemed to level off at vitamin D levels of 18 ng/mL or more, regardless of calcium intake. Increasing vitamin D did not further decrease PTH. A high serum PTH was associated with 800 mg/d calcium versus 1,200 mg/d of calcium only when vitamin D was less than 10 ng/mL.
"As long as vitamin D status is ensured, calcium intake levels of more than 800 mg/d may be unnecessary for maintaining calcium metabolism. Vitamin D supplements are necessary for adequate vitamin D status in northern climates," the authors conclude.
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