Vitamin D Status in Youth: Implications for Impaired Glucose Metabolism

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Vitamin D Status in Youth: Links with Adiposity, Insulin Sensitivity,

Ethnicity, Season: Implications for Impaired Glucose Metabolism

http://www.vitasearch.com/CP/weeklyupdates/

Reference: " Hypovitaminosis D in obese children and adolescents:

relationship with adiposity, insulin sensitivity, ethnicity, and

season, " Alemzadeh R, Kichler J, et al, Metabolism, 2008; 57(2):

183-191. (Address: Ramin Alemzadeh, Section of Pediatric Endocrinology

and Metabolism, Medical College of Wisconsin, Milwaukee, WI 53226, USA.

E-mail: ralemzad@... ).

Summary: In a study involving 127 pediatric subjects (mean age: 13

years; mean BMI: 36.4 kg/m(2); 61.2% female; 49 Caucasian, 39 Hispanic,

39 African-American), vitamin D status was found to be influenced by

vitamin D intake, season, ethnicity/race, and adiposity. Hypovitaminosis

D (serum 25(OH)D < 75 nmol/L) was found in 74% of subjects, vitamin D

insufficiency (serum 25(OH)D between 50 and 77.9 nmol/L) was found in

41.7% of subjects, and vitamin D deficiency (serum 25(OH)D less than 50

nmol/L) was found in 32.3% of subjects. Prevalence of both

hypovitaminosis D and vitamin D deficiency were more significant among

Hispanics (76.9%, 43.6%) and African-Americans (87.2%, 48.7%), than

Caucasians (59.1%, 10.2%). Prevalence of vitamin D insufficiency was

48.9% in Caucasians, 33.3% in Hispanics, and 38.5% in African-Americans.

Hypovitaminosis D and vitamin D deficiency were more prevalent in

fall/winter, as compared to spring/summer, while vitamin D insufficiency

was not significantly d ifferent between the seasons. Hypovitaminosis D,

vitamin D deficiency, and vitamin D insufficiency all corresponded to

vitamin D intake. Subjects with hypovitaminosis D and vitamin D

deficiency were found to have higher body mass index, higher fat mass,

higher iPTH, and lower QUICKI (quantitative insulin sensitivity check

index), as compared to subjects with vitamin D sufficiency (serum

25(OH)D of 75 nmol/L or higher). Fat mass was negatively associated with

25(OH)D and positively associated with iPTH. Serum 25(OH)D was

positively associated with QUICKI, negatively associated with hemoglobin

A1C, and negatively associated with iPTH - all regardless of season and

ethnic/racial background. The authors conclude, " …Obese children and

adolescents with low vitamin D status may be at increased risk of

developing impaired glucose metabolism independent of body adiposity.

Additional studies are needed to evaluate the underlying mechanisms. "

--

ne Holden, MS, RD

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