Vitamin D supplements are often prescribed to slow or prevent the development of obesity-related medical complications such as insulin resistance.
The study, published in Pediatric Obesity, is part of a series conducted by researchers from the Mayo Clinic investigating obesity in childhood.
According to the Centers for Disease Control and Prevention (CDC), obesity has more than doubled among children and quadrupled among adolescents over the past 30 years. JAMA states that 1 in 5 American adolescents is currently obese.
A number of observational studies have indicated that vitamin D deficiency may be associated with obesity-related medical complications, such as cardiovascular disease and insulin resistance. Many health care providers consequently recommend high-dose supplementation to slow or prevent such complications from developing.
These courses of vitamins can sometimes be more than five to ten times the recommended daily intake.
Dr. Seema Kumar, a pediatric endocrinologist in the Mayo Clinic Children's Center, is yet to discover any significant benefit from vitamin D supplements in adolescents, however, after conducting four clinical trials and publishing six studies on the subject in the past 10 years.
"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," states Dr. Kumar.
The most common and efficient source of vitamin D is sunlight, with the richest food sources being fish oil and fatty fish. If an individual is unable to obtain their recommended amounts of the vitamin from natural sources, they are advised to use vitamin D supplements.
Vitamin D supplementation linked to rises in cholesterol and triglycerides
For her team's most recent study, they examined the effect of vitamin D supplementation in 19 obese adolescents aged 13-18 with vitamin D deficiency, assessing what influence - if any - it had on their overall health.
After 3 months of boosting the teens' vitamin D levels into the normal range with supplements, the researchers observed no changes in body weight, body mass index (BMI), waistline, blood pressure or blood flow, Dr. Kumar explains. She says that she was surprised not to have uncovered any health benefit.
Fast facts about vitamin D
- Vitamin is also known as the sunshine vitamin
- Despite its name, vitamin D is considered to be a pro-hormone and not actually a vitamin
- Some experts believe vitamin D could protect against diseases such as cancer and multiple sclerosis.
Ingesting too much vitamin D can lead to a condition known as vitamin D toxicity or hypervitaminosis, potentially resulting in nausea, vomiting and kidney complications. However, the new study also found increased cholesterol and triglycerides - a fat found in the blood that can increase heart disease risk - among the participants.
Dr. Kumar suggests that this finding could be due to the relatively small number of children participating in the study and its short timeframe. To address these limitations, she calls for larger, placebo-controlled studies to investigate the long-term effects of vitamin D supplementation.
"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," Dr. Kumar concludes. "We're just saying the jury is still out on how useful it is for improving overall health in adolescents."
Recently, Medical News Today reported on a study suggesting that high-dose vitamin D supplements do not improve bone health for postmenopausal women - a group that is particularly susceptible to conditions such as osteoporosis.
Vitamin D insufficiency is estimated to affect around 75% of postmenopausal women in the US. The effect of this deficiency on skeletal health is exacerbated by the falling estrogen levels that are also a factor in osteoporosis development.