Biochemical and clinical deficiency is uncommon in African immigrants despite a high prevalence of low vitamin D: the Africans in America study.
Osteoporos Int. 2015 May 23. [Epub ahead of print]
Thoreson CK1, Chung ST, Ricks M, Reynolds JC, Remaley AT, Periwal V, Li Y, Sumner AE.
1Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes, Digestive and Kidney Diseases (NIDDK), National Institutes of Health (NIH), Bld 10-CRC, Rm 6-5940, MSC 1612, 9000 Rockville Pike, Bethesda, MD, 20892-1612, USA.
African ancestry is associated with low vitamin D levels but high bone density. Fifty percent of African immigrants had low vitamin D levels, but <10 % had evidence of deficiency. The value of providing vitamin D supplementation to African immigrants without evidence of deficiency needs to be determined.
The Endocrine Society and Institute of Medicine (IOM) have concluded from studies in largely white populations that 25(OH)D is necessary for bone health. However, their definition of vitamin D insufficiency differs. The Endocrine Society recommends a 25(OH)D threshold of <30 ng/mL. The IOM uses a lower threshold of 25(OH)D of <20 ng/mL. As African ancestry is associated with decreased 25(OH)D but increased bone mineral density (BMD), the applicability of these thresholds to Africans is unknown. Therefore, we examined in African immigrants the relationship of 25(OH)D to parathyroid hormone (PTH) and BMD.
One hundred eighty-six African immigrants(69 % male, age 38 ± 10 (mean ± SD), range 20-64 years) living in metropolitan Washington, DC, were enrolled. BMD was determined from whole-body dual-energy X-ray absorptiometry (DXA) scans. Decreased BMD required T-scores ≤-1.0. The threshold for low 25(OH)D was the concentration of 25(OH)D at which PTH became suppressed. This is known as the inflection point. Biochemical deficiency required low 25(OH)D and PTH of >65 pg/mL. Clinical deficiency required low 25(OH)D and T-scores ≤-1.0.
25(OH)D <30 and <20 ng/mL occurred in 83 and 46 % of African immigrants, respectively. PTH inversely correlated with 25(OH)D (r = -0.31, P = 0.002). The inflection point occurred at a 25(OH)D concentration of 20 ng/mL. Biochemical and clinical deficiency occurred in only 8 and 3 % of immigrants, respectively.
As PTH became suppressed at 25(OH)D of 20 ng/mL, the 25(OH)D <20 ng/mL threshold for insufficiency may apply to African immigrants. However, ~50 % of African immigrants have 25(OH)D <20 ng/mL, but only <10 % had evidence of deficiency. The value of providing vitamin D supplementation to the large number of African immigrants with 25(OH)D <20 ng/mL and no detectable evidence of deficiency needs to be determined.
- African-Americans need only 20 ng of vitamin, not 30 ng, based on iPTH – Sept 2012
Unknown - how much vitamin D needed for non-iPTH concerns, such as the following
- Dark-skined mothers: preeclampsia 12X more likely if gestational hypertension – May 2014
- Depression in pregnant blacks strongly associated to vitamin D levels – Nov 2012
- Dark skin births are much riskier due to lack of vitamin D
- Colon cancer more likely in blacks due to differences in Vitamin D genes (wonder if more Vitamin D would help) – May 2014
- Vitamin D deficiency diseases in dark skinned people living far from equator – Meta-analysis Oct 2013
- Dark skinned in Norway: 1000 IU vitamin D not enough to reduce pain – RCT Sept 2014
- Most immigrant women in Sweden had little vitamin D and lots of muscle pain – May 2013