Here's an example of how one needs to be careful about interpreting studies.
Vitamin D Status and Its Relationship to Body Fat, Final Height, and Peak Bone Mass in Young Women
Context: Vitamin D insufficiency has now reached epidemic proportions and has been linked to low bone mineral density, increased risk of fracture, and obesity in adults. However, this relationship has not been well characterized in young adults.
Objective: The objective of the study was to examine the relationship between serum 25-hydroxyvitamin D (25OHD), anthropometric measures, body fat (BF), and bone structure at the time of peak bone mass.
Design: This was a cross-sectional study.
Outcome Measures and Subjects: Anthropometric measures, serum 25OHD radioimmunoassay values, and computed tomography and dual-energy x-ray absorptiometry values of BF and bone structure in 90 postpubertal females, aged 16–22 yr, residing in California were measured.
Results: Approximately 59% of subjects were 25OHD insufficient (29 ng/ml), and 41% were sufficient (30 ng/ml). Strong negative relationships were present between serum 25OHD and computed tomography measures of visceral and sc fat and dual-energy x-ray absorptiometry values of BF. In addition, weight, body mass, and imaging measures of adiposity at all sites were significantly lower in women with normal serum 25OHD concentrations than women with insufficient levels. In contrast, no relationship was observed between circulating 25OHD concentrations and measures of bone mineral density at any site. Unexpectedly, there was a positive correlation between 25OHD levels and height.
Conclusions: We found that vitamin D insufficiency is associated with increased BF and decreased height but not changes in peak bone mass.
While it's tempting to jump on such news — there's already plenty of well-established reasons to get vitamin D levels up anyway — studies like this don't do much for me.
Note where the study was done: [sunny] California, which, I might add, has been breaking temperature records lately — high 70s in mid-January in San Jose. I'm in the mountains right now, 4,500 feet, and it's a beautiful bright & sunny 55 outside. And, when was the study done, summer, winter, spring or fall? Doesn't say.
So, is it the higher D levels causing lower body fat and increased height, or is it just more likely that tall slender girls (16-22) go to the beach and other places to bare their skin and model their bodies more often than short fat girls?