Recently, a study about vitamin D in obese adolescents made worldwide news.
There were at least 109 more articles in the press warning teenagers about the potential harmful effects of vitamin D.
What is it that causes a press feeding frenzy? If you look at the study in question, it is an open label trial of 19 obese adolescents using 100,000 IU/month for 3 months:
The results from this study showed a marginally significant increase in cholesterol and triglycerides. However, it did show a clearly significant decrease in parathyroid hormone (PTH). High PTH has repeatedly been associated with cardiovascular disease.
This was not a randomized controlled trial (RCT); it was an open label, non-blinded, non-controlled, non-randomized trial. It was not a trial of 200 obese adolescents; it was 19 obese adolescents. It did not use daily vitamin D in adequate doses; it used bolus or stoss dosing. The study did not exclude vitamin D sufficient participants, instead both vitamin D sufficient and deficient individuals were treated.
What do other studies show? In particular, what do RCTs show?
Where was the press when a RCT of 4,000 IU/day for 6 months in obese adolescents showed vitamin D significantly improved insulin sensitivity?
Belenchia AM, Tosh AK, Hillman LS, Peterson CA. Correcting vitamin D insufficiency improves insulin sensitivity in obese adolescents: a randomized controlled trial. Am J Clin Nutr. 2013 Apr;97(4):774-81.
Where was the press when a RCT of 2,000 IU/day for 12 weeks in obese adolescents showed no effect on triglycerides or cholesterol?
Nader NS, Aguirre Castaneda R, Wallace J, Singh R, Weaver A, Kumar S. Effect of vitamin D3 supplementation on serum 25(OH)D, lipids and markers of insulin resistance in obese adolescents: a prospective, randomized, placebo-controlled pilot trial. Horm Res Paediatr. 2014;82(2):107-12.
Where was the press when a RCT of 4,000 IU/day for 6 months in postmenopausal women showed vitamin D significantly lowers serum triglycerides?
Muñoz-Aguirre P, Flores M, Macias N, Quezada AD, Denova-Gutiérrez E, Salmerón J. The effect of vitamin D supplementation on serum lipids in postmenopausal women with diabetes: A randomized controlled trial. Clin Nutr. 2014 Oct 13. pii: S0261-5614(14)00254-4.
Where was the press when a RCT of 50,000 IU every 3 weeks for 6 weeks in gestational diabetes showed vitamin D significantly lowered LDL and triglycerides?
Asemi Z, Hashemi T, Karamali M, Samimi M, Esmaillzadeh A. Effects of vitamin D supplementation on glucose metabolism, lipid concentrations, inflammation, and oxidative stress in gestational diabetes: a double-blind randomized controlled clinical trial. Am J Clin Nutr. 2013 Dec;98(6):1425-32.
These 109 press articles about this study represented a typical press feeding frenzy that emphasized the danger of vitamin D. It is important for readers to critically evaluate these studies before blindly accepting the headlines.