Adequacy of vitamin D replacement in severe deficiency is dependent on body mass index.
BACKGROUND
Obesity is associated with hypovitaminosis D. Whether body mass index (BMI) determines the replacement dose of vitamin D to achieve sufficiency is unclear.


OBJECTIVE
To determine the relationship between BMI and serum 25-OH vitamin D concentrations and whether the increase in serum 25-OH vitamin D concentrations with vitamin D replacement is dependent on BMI.


METHODS
Retrospective review of anthropometric data and serum 25-OH vitamin D concentrations in 95 patients attending an outpatient clinic in a tertiary hospital. In a second component of the study, 17 hospital inpatients with severe vitamin D deficiency (serum 25-OH D concentrations<6 ng/mL [15 nmol/L]) were supplemented with 10,000 units vitamin D(3)/day orally for 1 week. Biochemistry and anthropometric measurements were compared before and after vitamin D replacement.


RESULTS
Serum 25-OH vitamin D concentrations correlated negatively with BMI in the 95 outpatients (r(2) = 0.11, P <.01). In the longitudinal study, BMI correlated positively with serum intact parathyroid hormone (r(2) = 0.84, P <.01) and negatively with 1.25-(OH)(2) vitamin D (r(2) = 0.19, P=.06) at baseline. Serum 25-OH D concentrations achieved following 1 week of vitamin D(3) replacement correlated negatively with BMI (r(2) = 0.63, P <.01).


CONCLUSIONS
Efficacy of vitamin D supplementation is dependent on BMI. Overweight and obese patients with hypovitaminosis D might require higher doses of vitamin D to achieve vitamin D repletion compared with individuals with normal body weight.
Department of Endocrinology, St Vincent's Hospital, 384 Victoria Street, Sydney, New South Wales, Australia 2010. p.lee@garvan.org.au
Paul
P
Lee
Jerry R
JR
Greenfield
Markus J
MJ
Seibel
John A
JA
Eisman
Jacqueline R
JR
Center
D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D004305:Dose-Response Relationship, Drug; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications / Q000378:metabolism; D011863:Radioimmunoassay; D012189:Retrospective Studies; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D016896:Treatment Outcome; D014807:Vitamin D / Q000008:administration & dosage*; D014808:Vitamin D Deficiency / Q000097:blood / Q000188:drug therapy* / Q000209:etiology; D014815:Vitamins / Q000008:administration & dosage*
D014815:Vitamins; D014807:Vitamin D