Obese need 2.5 IU of vitamin D per kg to increase 1 ng (about 3.4 X more) – RCT Sept 2013

25-hydroxyvitamin D Response to Graded Vitamin D3 Supplementation Among Obese Adults

The Journal of Clinical Endocrinology & Metabolism September 13, 2013 jc.2012-4103
Andjela Drincic, M.Da,
Eileen Fuller, M.D b,
Robert P. Heaney, M.Db and
Laura A.G. Armas, M.D, M.Sb
A University of Nebraska Medical Center;
B Osteoporosis Research Center, Creighton University
Address all correspondence and requests for reprints to: Andjela Drincic, M.D. 984120 Nebraska Medical Center, Omaha, NE 68198–4120, E-mail: andjela.drincic at unmc.edu or phone: 402 559 8176 or Fax: 402 559 9003.

Context: Guidelines have suggested that obese adults need two to three times more vitamin D than lean adults to treat vitamin D deficiency, but few studies have evaluated the vitamin D dose response in obese subjects.

Objective: The purpose of this study was to characterize the pharmacokinetics of 25(OH)D response to 3 different doses of vitamin D3 (cholecalciferol) in a group of obese subjects and to quantify the 25(OH)D dose response relationship.

Design, Setting, Intervention, Patients: This was a randomized, single blind study of 3 doses of oral vitamin D3 (1,000 IU, 5,000 IU, or 10,000 IU) given daily to 67 obese subjects for 21 weeks during the winter months.

Main Outcome Measures: Serum 25(OH)D levels were measured at baseline and after vitamin D replacement, and 25(OH)D pharmacokinetic parameters were determined, fitting the 25(OH)D concentrations to an exponential model.

Results: Mean measured increments in 25(OH)D at week 21 were: 12.4- (SD 9.7) ng/ml in the 1,000 IU/d group, 27.8 (SD10.2) ng/mL in the 5,000 IU/d group, and 48.1(SD 19.6) ng/ml in the 10,000 IU/d group. Steady state increments computed from the model were 20.6 (SD 17.1) ng/ml, 35.2 (SD 14.6) ng/ml, and 51.3 (SD 22.0) ng/ml, respectively. There were no hypercalcuria or hypercalcemia events during the study.

Conclusion: Our data show that in obese people the 25(OH)D response to vitamin D3 is directly related to dose and body size with ∾ 2.5 IU/kg required for every unit increment in 25(OH)D (ng/ml).

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Rule of thumb for adult normall is independent of weight = 100 IU for 1 ng increase
This study found a rule of obese thumb of 2.5 IU/kg (independent of vitamin D level)
Thus, 300 lb (136 kg) person would require 340 IU per ng
   300 lb person wanting to increase blood level by 30ng would need to add 10,200 IU (340X30)
    And should start with a loading dose if he wanted to get to that blood level in < 3 months

See also VitaminDWiki

• Endocrine Society Guideline should be raised to 2 ng per 100 IU of vitamin D – March 2013
• Obese need 2X to 3X more vitamin D - Nov 2014
• Search VitaminDWiki for Heaney and Obese 404 results Sept 2013
• Interview of Dr. Robert Heaney, MD – March 2013
• Vitamin D Insufficiency is less than 32 or 40 ng – Heaney 2012
• Defining normal level of vitamin D (need 4000-5000 IU) - Heaney Spring 2013 from his blog
• Vitamin D should be 48 ng to 90 ng – Heaney Sept 2011
• Obese need 2X as much vitamin D to get the same response – June 2012
• 50,000 IU vitamin D weekly increased levels by 52 ng normally, but only 28 ng if obese – Oct 2013
• Dose response equation square root of IU
• All items in category Predict Vitamin D 82 items
• Overview Vitamin D Dose-Response which has the following graph, which show that linear response ratio which varies with the dose size