Circulating vitamin D3 and 25-hydroxyvitamin D in humans: An important tool to define adequate nutritional vitamin D status - PubMed (original) (raw)

Circulating vitamin D3 and 25-hydroxyvitamin D in humans: An important tool to define adequate nutritional vitamin D status

Bruce W Hollis et al. J Steroid Biochem Mol Biol. 2007 Mar.

Abstract

Circulating 25-hydroxyvitamin D [25(OH)D] is generally considered the means by which we define nutritional vitamin D status. There is much debate, however, with respect to what a healthy minimum level of circulation 25(OH)D should be. Recent data using various biomarkers such as intact parathyroid hormone (PTH), intestinal calcium absorption, and skeletal density measurements suggest this minimum level to be 80 nmol (32 ng/mL). Surprisingly, the relationship between circulating vitamin D(3) and its metabolic product-25(OH)D(3) has not been studied. We investigated this relationship in two separate populations: the first, individuals from Hawaii who received significant sun exposure; the second, subjects from a lactation study who received up to 6400IU vitamin D(3)/day for 6 months. Results (1) the relationship between circulating vitamin D(3) and 25(OH)D in both groups was not linear, but appeared saturable and controlled; (2) optimal nutritional vitamin D status appeared to occur when molar ratios of circulating vitamin D(3) and 25(OH)D exceeded 0.3; at this point, the V(max) of the 25-hydroxylase appeared to be achieved. This was achieved when circulating 25(OH)D exceeded 100 nmol. We hypothesize that as humans live today, the 25-hydroxylase operates well below its V(max) because of chronic substrate deficiency, namely vitamin D(3). When humans are sun (or dietary) replete, the vitamin D endocrine system will function in a fashion as do these other steroid synthetic pathways, not limited by substrate. Thus, the relationship between circulating vitamin D and 25(OH)D may represent what "normal" vitamin D status should be.

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Figures

Figure 1

Figure 1. Circulating 25(OH)D as a Function of Vitamin D3 Status in Subjects from a Sun-Rich Environment

Circulating 25(OH)D as a function of circulating vitamin D3 in a sun-exposed population. Best-fit regression analysis yielded the equation y=21.5 + 1.6X − 0.02X2, r2=0.75, n=20.

Figure 2

Figure 2. Circulating 25(OH)D as a Function of Vitamin D3 Status in Supplemented Subjects

Circulating 25(OH)D as a function of circulating vitamin D3 in high dose (6,400 IU vitamin D3/day) subjects. Best-fit regression analysis yielded the equation y = 30.8 + 0.7x − 0.01X2, r2= 0.60, n=82.

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References

    1. Haddad JG, Chyu K. Competitive protein-binding radioassay for 25-hydroxycholecalciferol. J Clin Endocrinal Metab. 1971;33:992–995. - PubMed
    1. Bischoff-Ferrari H, Dietrich T, Orav E, Dawson-Hughes B. Positive association between 25(OH)D levels and bone mineral density: A population-based study of younger and older adults. Amer J Med. 2004;116:634–639. - PubMed
    1. Fuleihan E, Nabulsi M, Tamim H, Maalouf J, Salamoun M, Khalife H, et al. Effect of vitamin D replacement on musculoskeletal parameters in school children: A randomized controlled trial. J Clin Endocrinal Metab. 2006;91:405–412. - PubMed
    1. Javaid M, Crozier S, Harvey N, Gale C, Dennison E, Boucher B, et al. Maternal vitamin D status during pregancy and childhood bone mass at 9 years: A longitudinal study. Lancet. 2006;367:36–43. - PubMed
    1. Heaney R, Dowell M, Hale C, Bendich A. Calcium absorption varies within the reference range for serum 25-hydroxyvitamin D. J Amer College Nutr. 2003;22(2):142–146. - PubMed

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