Surprising results in a series of studies in juvenile obesity at the Mayo Clinic in Rochester, Minnesota, find that vitamin D supplementation for obese teens shows no benefits for the subjects’ heart health or risk of developing diabetes. It was also found that dosing with vitamin D could actually result in the unintended consequences of increasing cholesterol and fat-storing triglycerides.
Study leader Seema Kumar, M.D. , a pediatric endocrinologist in the Mayo Clinic Children’s Center, has been studying effects of vitamin D supplementation in children for a decade, through four clinical trials and six published studies, and to date, she and her team have observed limited benefit from vitamin D supplements in adolescents. The latest study, entitled “Effect of Vitamin D3 Treatment on Endothelial Function in Obese Adolescents“ (DOI: 10.1111/ijpo.12059), was published online before print on August 14 in in the journal Pediatric Obesity. The Original Research paper is coauthored by Dr. Kumar and A. Javed of the Division of Pediatric Endocrinology, Department of Pediatric and Adolescent Medicine at the Mayo Clinic, I. J. Kullo of the Division of Cardiovascular Diseases at the Mayo Clinic Department of Internal Medicine, and P. Babu Balagopal of the Division of Biomedical Research at the Nemours Children’s Clinic in Jacksonville, Florida. The trial was registered on clinical trials.gov (NCT01746264).
The study’s aim was to determine whether vitamin D3 supplementation would improve endothelial function in obese adolescents, since obesity in children is associated with vitamin D deficiency and endothelial dysfunction.
Nineteen subjects aged 13 to 18 years of age, with 25-hydroxy vitamin D (25[OH]D) levels were chosen for the study.
“After three months of having vitamin D boosted into the normal range with supplements, these teenagers showed no changes in body weight, body mass index, waistline, blood pressure or blood flow,” says Dr. Kumar. “We’re not saying the links between vitamin D deficiency and chronic diseases don’t exist for children; we just haven’t found any yet.”
The Mayo research team concluded that treatment with vitamin D3, 100,000 IU once a month for three months was effective in increasing 25(OH)D levels in obese adolescents but did not impact endothelial function.
According to the Journal of American Medical Association, one in five American adolescents is obese, and more than a third are overweight, with several observational studies also having noted links between vitamin D deficiency and a host of weight-related medical complications, including cardiovascular diseases and insulin resistance. Consequently, caregivers and providers often start high-dose supplementation in an attempt to slow or reverse some of the clinical complications associated with obesity.
“I have been surprised that we haven’t found more health benefit,” says Dr. Kumar in a Mayo Clinic release. “We’re not saying it’s bad to take vitamin D supplements at reasonable doses, and we know most obese teens are vitamin D deficient. We’re just saying the jury is still out on how useful it is for improving overall health in adolescents.”
This was the first of Dr. Kumar’s studies to report increased cholesterol and triglycerides during vitamin D supplementation, a finding she says might be attributed to the smaller number of children who participated in the study and the relatively short timeframe. She says there needs to be larger, placebo-controlled studies to examine the long-term effects of vitamin D supplementation on teens and children.
“Parents and providers often put obese adolescent children on vitamin D regimens sometimes at more than 5-to-10 times the recommended daily intake because some studies have shown a link between vitamin D in the blood and improved vascular function,” says Dr. Kumar, explaining that she opted to study vitamin D in overweight teens because they are a demographic at increased risk for chronic disease, and because of vitamin D’s increasing popularity as a complementary treatment for obesity.
However, Dr. Kumar cautions that it is possible to ingest too much vitamin D, a condition called vitamin D toxicity or hypervitaminosis, the main consequences of which can include a buildup of calcium in the blood (hypercalcemia), which in turn can cause poor appetite, nausea and vomiting. Weakness, frequent urination and kidney problems also may occur, which can result in poor appetite, nausea, vomiting and kidney complications. For more information on hypervitaminosis, click here.
Journal of American Medical Association