October 23, 2014

expert reaction to obesity, diabetes and UV light

A study in the journal Diabetes has looked at the effects of vitamin D supplements or exposure to UV light on metabolic phenotypes in mice, such as obesity and type 2 diabetes. The researchers suggest that while vitamin D supplements are often taken to combat deficiency, they do not reproduce the positive effects of exposure to UV radiation in sunlight in terms of these disorders.

Dr Colin Michie, Paediatrician and Chair of the Nutrition Committee, Royal College of Paediatrics and Child Health, said:

“The photobiology of the skin is a complex process. We know that ultraviolet light has significant effects on widely differing processes including inflammation, endorphins, steroid biochemistry and malignancy. It is therefore not surprising, from an evolutionary perspective, that this form of irradiation can influence systemic malaise such as the metabolic syndrome and obesity. The paper by Geledenhuys and colleagues is of considerable value in moving this subject from molecules into organisms. It raises critical questions for us humans – are the effects the same in our children and ourselves, and, if so, can they be applied to prevent obesity, treat metabolic syndrome and save vast amounts of pharmacological treatment? The script further helps answer conundrums that have arisen from studies with vitamin D supplementation.  Perhaps it is just a little sunshine that we require.”

Prof David Ray, Professor of Medicine and Endocrinology, Institute of Human Development, University of Manchester, said:

“This is an important study which shows that lifestyle factors beyond diet can help prevent weight gain, and diabetes. These findings support the idea that a healthy lifestyle should include time outside in the sunshine, not only for exercise, but also to benefit from sunlight on skin. There are also clear implications for high risk groups, such as Muslim women who are covered, who do not get sunlight on their skin, but may in the future benefit from drug intervention.

“Sunlight and vitamin D have been controversial in the past. Excess sunlight causing burns is a risk for melanoma, but we get most of our vitamin D from sunlight, so that in NW England about 1 in 3 are vitamin D deficient, with implications for bone health. There has been much research showing that low vitamin D is found in groups of people with disease, but it is unclear if this is because sick people get out less, and so end up with less vitamin D, or whether vitamin D actually plays a role in disease. Low vitamin D may just be a marker of people at high risk of disease due to other things, such as occupation, poverty etc. A strength of this study is that the authors have specifically looked to see if vitamin D is required for the UV effect, and found that actually it is the nitric oxide that is important.  This is critical, as previous studies have not distinguished cause-effect from a simple association.”

‘Ultraviolet radiation supresses obesity and symptoms of metabolic syndrome independently of vitamin D in mice fed a high-fat diet’ by Geldenhuys et al. published in Diabetes on Thursday 23^rd October 2014. 

Declared interests

None declared