The discrepancy between observational and intervention studies suggests that low 25(OH)D is a marker of ill health .
Inflammatory processes involved in disease occurrence and clinical course would reduce 25(OH)D , which would explain why low vitamin D status is reported in a wide range of disorders .
In elderly people , restoration of vitamin D deficits due to ageing and lifestyle changes induced by ill health could explain why low-dose supplementation leads to slight gains in survival
Low serum concentrations of 25-hydroxyvitamin D ( 25[OH]D ) have been associated with many non-skeletal disorders .
However , whether low 25(OH)D is the cause or result of ill health is not known .
C-reactive protein, interleukin 6, and risk of developing type 2 diabetes mellitus.
CONTEXT Inflammation is hypothesized to play a role in development of type 2 diabetes mellitus ( DM ) ; however , clinical data addressing this issue are limited . OBJECTIVE To determine whether elevated levels of the inflammatory markers interleukin 6 ( IL-6 ) and  C-reactive protein ( CRP ) are associated with development of  type 2 DM in healthy middle-aged women . DESIGN Prospect i ve , nested case-control study . SETTING The Women 's Health Study , an ongoing US primary prevention , r and omized clinical trial initiated in 1992 . PARTICIPANTS From a nationwide cohort of 27 628 women free of diagnosed DM , cardiovascular disease , and cancer at baseline , 188 women who developed diagnosed DM over a 4-year follow-up period were defined as cases and matched by age and fasting status with 362 disease-free controls . MAIN OUTCOME MEASURES Incidence of confirmed clinical ly diagnosed type 2 DM by baseline levels of IL-6 and CRP . RESULTS Baseline levels of IL-6 ( P<.001 ) and CRP ( P<.001 ) were significantly higher among cases than among controls . The relative risks of future DM for women in the highest vs lowest quartile of these inflammatory markers were 7.5 for IL-6 ( 95 % confidence interval [ CI ] , 3.7 - 15.4 ) and 15.7 for CRP ( 95 % CI , 6.5 - 37.9 ) . Positive associations persisted after adjustment for body mass index , family history of diabetes , smoking , exercise , use of alcohol , and hormone replacement therapy ; multivariate relative risks for the highest vs lowest quartiles were 2.3 for IL-6 ( 95 % CI , 0.9 - 5.6 ; P for trend = .07 ) and 4.2 for CRP ( 95 % CI , 1.5 - 12.0 ; P for trend = .001 ) . Similar results were observed in analyses limited to women with a baseline hemoglobin A(1c ) of 6.0 % or less and after adjustment for fasting insulin level . CONCLUSIONS Elevated levels of CRP and IL-6 predict the development of type 2 DM . These data support a possible role for inflammation in diabetogenesis
The discrepancy between observational and intervention studies suggests that low 25(OH)D is a marker of ill health .
Inflammatory processes involved in disease occurrence and clinical course would reduce 25(OH)D , which would explain why low vitamin D status is reported in a wide range of disorders .
In elderly people , restoration of vitamin D deficits due to ageing and lifestyle changes induced by ill health could explain why low-dose supplementation leads to slight gains in survival
Low serum concentrations of 25-hydroxyvitamin D ( 25[OH]D ) have been associated with many non-skeletal disorders .
However , whether low 25(OH)D is the cause or result of ill health is not known .