Vitamin D insufficiency in young women is associated with increased body fat and decreased height but not with changes in peak bone mass, report researchers.
“Vitamin D insufficiency has now reached epidemic proportions and has been linked to low bone mineral density (BMD), increased risk for fracture, and obesity in adults,” comment Vicente Gilsanz (Childrens Hospital Los Angeles, California, USA) and colleagues.
To investigate this relationship in young adults, Gilsanz and team measured serum 25-hydroxyvitamin D (25-OHD) levels, body mass index (BMI), body fat and BMD in 90 post-pubertal females, aged between 16 and 22 years.
To account for the influence of soft tissues on dual X-ray absorptiometry (DXA) bone measurements, the researchers examined the association between vitamin D, bone health and adiposity by using both DXA and computed tomography (CT).
Thirty-seven (41%) women had normal 25-OHD concentrations (30 ng/ml or more), while 53 (59%) women were considered to be 25-OHD insufficient (29 ng/ml or less). The vitamin D insufficient women were significantly shorter, heavier, and had a greater BMI than the women with normal 25-OHD values.
CT measurements for visceral and subcutaneous fat and DXA values for body fat were significantly lower in women with normal serum 25-OHD concentrations than women with insufficient levels.
In contrast, no relationship was observed between circulating 25-OHD concentrations and measures of BMD at any site.
This result is “intriguing,” remark Gilsanz et al, because “previous investigations in adults have indicated that vitamin D supplementation improved BMD and reduced the risk for osteoporosis and fractures.”
This supports the hypothesis that “the negative effect of vitamin D insufficiency on bone mass may not be present in healthy young adults around the time that bone mass reaches its peak,” they add.
Another unexpected finding was a positive correlation between 25-OHD levels and height. The researchers were unable to explain this association and suggest “further studies are needed to determine the possible role of vitamin D in longitudinal bone growth in the absence of clinical evidence of rickets.”
The results are published in the Journal of Clinical Endocrinology and Metabolism.