Vanguard Neurologist

“Vitamin D insufficiency has now reached epidemic proportions and has been linked to low bone mineral density (BMD), increased risk of fracture and obesity in adults,” write Richard Kremer, MD, PhD, from McGill University Health Center in Montreal, Canada, and colleagues. “However, this relationship has not been well characterized in young adults.”

The goal of this study was to assess the association between serum 25-hydroxyvitamin D [25(OH)D] determined by radioimmunoassay, anthropometric measures, and computed tomography (CT) and dual-energy x-ray absorptiometry (DXA) values of body fat and bone structure at the approximate time of peak bone mass. The study sample consisted of 90 postpubertal women aged 16 to 22 years and living in California.

Insufficiency of 25(OH)D, defined as a serum level of 29 ng/mL or less, was present in approximately 59% of participants, and the remaining 41% had sufficient 25(OH)D levels, defined as a serum level of 30 ng/mL or more. Serum 25(OH)D levels were strongly negatively related to CT measures of visceral and subcutaneous fat and to DXA values of body fat.

Compared with women with insufficient levels of serum 25(OH)D, those with normal serum 25(OH)D levels had significantly lower weight, body mass, and imaging measures of adiposity at all sites. However, circulating 25(OH)D concentrations were not related to measures of bone mineral density at any site. There was an unanticipated positive correlation between 25(OH)D levels and height.

“Our study indicates that vitamin D insufficiency is extremely common in young women living in a sun-rich area of the United States,” the study authors write. “It also supports the hypotheses that either vitamin D insufficiency is a risk factor for increased body fat or increased body fat is a risk factor for vitamin D insufficiency.”

Limitations of this study include insufficient power to analyze Caucasian and Hispanic participants separately and lack of generalizability to young men.

“The positive association between height and vitamin D status is unexplained and intriguing, and warrants further investigation,” the study authors conclude. “Our data, however, do not support a role for vitamin D in regulating bone mass acquisition around the time it reaches its peak.”