Vitamin D Recommendations and Assumptions

This is part of our ongoing The Best Kept Secrets to Healthy Aging spotlight. Each day, we will be posting some of the great information that’s packed into our book, The Best Kept Secrets to Healthy Aging.

Today’s topic:
Vitamin D Recommendations and Assumptions

Many scientists now think that one way to ensure that someone’s vitamin D health is optimized is to recommend that the person consume enough vitamin D to prevent more than a trickle of parathyroid hormone (PTH) from being released by the parathyroid glands. PTH is selected as the biomarker for vitamin D adequacy because the parathyroid glands secrete PTH when they sense that the concentration of calcium in the blood is getting too low to be able to support brain and heart muscle function. PTH is the hormone that 1) triggers renal conversion of 25(OH)D3 to 1,25(OH)2D3 in order to increase the efficiency of absorption of dietary calcium (usually only 20% to 40% of ingested calcium is absorbed so there’s plenty of room for improvement) and 2) itself causes bone tissue within existing bones to dissolve in order to add to the circulating supply of calcium. If vitamin D keeps the plasma calcium level high enough, the parathyroid glands sense that there is no need for them to secrete PTH – and less bone is destroyed in order to release its calcium. However, other biomarkers like PTH exist, and scientists are discovering that other biomarkers, such as the amount required so that breast milk has enough Vitamin D for the infant, require even high vitamin D blood levels to be satisfied, 7,000 IU/day in the case of breast feeding women.

Findings published recently in the Journal of Nutrition have shown conclusively that the density of skeletal bone begins to decline just when vitamin D intake becomes too low to prevent an increase in PTH secretion.11 On the other hand, recent findings published in the Journal of Bone and Mineral Metabolism demonstrate that the first measurable indicator of early vitamin D deficiency in adult human’s blood is an increase in PTH secretion.12 As confirmed by the results of studies published recently in the Journal of the American Medical Association and the Journal of Clinical Endocrinology and Metabolism, minimizing parathyroid secretion of PTH by optimizing vitamin D intake achieves a true healthful balance between the diet, vitamin D, calcium and the skeleton.13,14

Next  Best Kept Secrets to Healthy Aging topic:
So How Much Vitamin D Do I Need?

11. Hollis BW. Circulating 25-hydroxyvitamin D levels indicative of vitamin D sufficiency: Implications for establishing a new effective dietary intake recommendation for vitamin D. J Nutr 2005;135:317- 322.
12. Hashemipour S, Larijani B, Adibi H, Sedaghat M, Pajouhi M, Bastan- Hagh MH, Soltani A, Javadi E, Shafaei AR, Baradar-Jalili R, Hossein- Nezhad A. The status of biochemical parameters in varying degrees of vitamin D deficiency. J Bone Miner Metab 2006;24:213-218.
13. Steingrimsdottir L, Gunnarsson O, Indridason OS, Franzson L, Sigurdsson G. Relationship between serum parathyroid hormone levels, vitamin D sufficiency, and calcium intake. JAMA 2005;294:2336-2341.

14. Snijder MB, van Schoor NM, Pluijm SM, van Dam RM, Visser M, Lips P. Vitamin D status in relation to one-year risk of recurrent falling in older men and women. J Clin Endocrinol Metab 2006;91:2980-2985.

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