HOUSTON – Fifty-four percent of 219 obese adolescents being evaluated for bariatric surgery were deficient in vitamin D, including 9% who were severely deficient, a retrospective analysis of preoperative laboratory measures found.
Eighty-two percent of the adolescents had insufficient levels of 25-hydroxyvitamin D (25OHD) in their blood, Dr. Marisa Censani and her associates reported at the annual meeting of the Endocrine Society.
Dr. Marisa Censani
The findings are so striking that all morbidly obese adolescents should be screened for vitamin D deficiency, and those who are deficient should be treated to replete vitamin D levels, suggested Dr. Censani of Columbia University, New York.
It’s particularly important to screen adolescents before bariatric surgery procedures, some of which have been associated with bone loss, which results from weight loss and decreased calcium and vitamin D absorption. Preoperative vitamin D deficiency could put adolescent patients at greater risk because they have not reached their peak bone mass, she said.
Previous studies have shown that obese adults undergoing bariatric surgery commonly are vitamin D deficient before surgery, but these are some of the first data in preoperative adolescent patients.
Of all adolescents undergoing bariatric surgery at her institution from March 2006 to June 2011, 219 had records on serum 25OHD and parathyroid hormone levels. The cohort was 65% female, 43% white, 35% Hispanic, and 15% African American, with the rest being other races/ethnicities. Patients had a mean age of 16 years (ranging from 13-18 years) and a mean body mass index of 48 kg/m2.
The mean serum 25OHD level was 21 ng/mL, which was considered insufficient. The study defined adequate levels of serum 25OHD as at least 30 ng/mL, insufficient levels as 20-29 ng/mL, deficient levels as less than 20 ng/mL, and severely deficient levels as less than 10 ng/mL.
Only 18% of patients had sufficient 25OHD levels. Twenty-nine percent had insufficient levels, 45% were vitamin D deficient, and 9% were severely deficient.
Patients with the highest BMIs were most likely to have deficient levels of 25OHD. Every kilogram increase in BMI correlated with a 0.2-ng decrease in 25OHD levels, Dr. Censani said.
Vitamin D deficiency was most common in African Americans, 82% of whom were deficient and none of whom had levels in the normal range. Fifty-nine percent of Hispanics and 37% of whites had vitamin D deficiency. Race was the strongest predictor of 25OHD levels.
Roughly 80% of African American patients were deficient in vitamin D and the rest had insufficient levels. In Hispanics, nearly 60% were deficient in vitamin D, close to 25% had insufficient levels, and about 25% had adequate levels. In whites, deficient or insufficient levels each were seen in nearly 40% of patients, with adequate levels in more than 20%.
Clear secondary hyperparathyroidism was seen in 5% of patients, though serum parathyroid levels varied inversely with 25OHD. African American race, BMI, and parathyroid levels explained 21% of the variance in 25OHD levels between patients.
To be eligible for bariatric surgery, adolescents had to have reached Tanner stage IV or V and had to have a BMI greater than 50, or above 35 kg/m2 if they had comorbidities.
A physician in the audience challenged Dr. Censani’s recommendation that all obese adolescents be screened and possibly treated for vitamin D deficiency, saying there is no evidence yet of clinical benefit from that approach. Dr. Censani agreed that more research is needed to support this strategy.
The current study was limited by the lack of a community-based, nonobese control group and lack of data on dietary calcium and vitamin D intake, sun exposure, or bone mineral density. The study’s large size and relatively good ethnic diversity are strengths, she said.
The U.S. adolescent obesity rate has more than tripled in the past 30 years, with 16% of children and adolescents now overweight, 4% obese, and 4% morbidly obese, studies suggest.
Dr. Censani reported having no financial disclosures. The National Institutes of Health funded the study.