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S hining the L ight on S unshine: a systematic review of the influence of sun exposure on type 2 diabetes mellitus‐related outcomes
Author(s) -
ShoreLorenti Catherine,
Brennan Sharon L.,
Sanders Kerrie M.,
Neale Rachel E.,
Lucas Robyn M.,
Ebeling Peter R.
Publication year - 2014
Publication title -
clinical endocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.055
H-Index - 147
eISSN - 1365-2265
pISSN - 0300-0664
DOI - 10.1111/cen.12567
Subject(s) - observational study , medicine , confounding , vitamin d and neurology , type 2 diabetes , incidence (geometry) , diabetes mellitus , insulin , type 2 diabetes mellitus , endocrinology , physiology , physics , optics
Summary Prospective observational studies uniformly link vitamin D deficiency with the incidence of type 2 diabetes mellitus ( T 2 DM ), yet trials supplementing participants at risk of T 2 DM with vitamin D to reduce progression to T 2 DM have yielded inconsistent results. Inconsistencies between supplementation trials may be due to insufficient dosing or small sample sizes. Observational studies may also have reported spurious associations due to uncontrolled confounding by lifestyle or genetic factors. Alternatively, observational and intervention studies may not be entirely comparable. Observational studies show an association between higher vitamin D status, which is predominantly derived from sun exposure, and decreased incidence of T 2 DM . Trials intervene with vitamin D supplementation, and therefore may be missing alternate causes of the effect of sun exposure, as seen in observational studies. We propose that sun exposure may be the driving force behind the associations seen in observational studies; sun exposure may have additional benefits beyond increasing serum 25‐hydroxyvitamin D (25 OHD ) levels. We performed an electronic literature search to identify articles that examined associations between sun exposure and T 2 DM and/or glucose metabolism. A best evidence synthesis was then conducted using outcomes from analyses deemed to have high methodological quality. Ten eligible full‐text articles were identified, yielding 19 T 2 DM ‐related outcomes. The best evidence analysis considered 11 outcomes which were grouped into six outcome types: T 2 DM , fasting glucose, glucose tolerance, fasting insulin, insulin secretion and insulin sensitivity. There was moderate evidence to support a role of recreational sun exposure in reducing odds of T 2 DM incidence. High‐level evidence was lacking; evidence presented for other outcomes was of low or insufficient level. This review highlights significant gaps in research pertaining to sun exposure and T 2 DM ‐related outcomes. Further research is encouraged as we aim to identify novel preventative strategies for T2 DM .