Vitamin D and Type 2 Diabetes

Are We Ready for a Prevention Trial?

  1. Robert Scragg
  1. From the School of Population Health, University of Auckland, Auckland, New Zealand
  1. Corresponding author: Robert Scragg, r.scragg{at}

Diabetes rates are increasing around the world, mainly driven by increasing levels of obesity (1). The dilemma for diabetes prevention is that the main risk factor—obesity—is a product of our modern lifestyle (the so-called obesogenic environment) (2). Immediate prospects for changing the environment to reverse rising obesity levels are not promising, and there is a need to consider other options for preventing diabetes.

One of these options—vitamin D—is addressed in the article by Forouhi et al. (3) in the current issue of Diabetes. The sun is the primary source of vitamin D, which is synthesized endogenously in skin to produce cholecalficerol (vitamin D3), although a small proportion (<20%) of vitamin D comes through diet from a limited range of foods (in the form of ergocalciferol [vitamin D2] and vitamin D3) (4). The main marker of vitamin D status is the metabolite 25-hydroxyvitamin D [25(OH)D], which is synthesized in the liver. The epidemiology of vitamin D status is inverse to that of diabetes, since blood levels of 25(OH)D decline with age and are lower in populations with increased skin pigmentation, such as African Americans and South Asians, and in people with obesity, while diabetes increases with age and obesity and is higher in these ethnic groups (5).

Animal studies published nearly 30 …

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