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 .
Randomized clinical trials. Perspectives on some recent ideas.
In spite of the controversy over the role of r and omized clinical trials  in medical research , the rationale underlying such trials remains persuasive as compared to recent suggestions for alternative non-r and omized studies such as those relying on the use of historical controls and adjustment technics . Others have suggested that recent statistical innovations for improving clinical trials , including adaptive allocation of treatment to patients and sequential stopping procedures , are underutilized . These innovations , though theoretically interesting , are not easily adapted to large-scale , complex medical trials in which there may be multiple end points and delayed response times . Ethical considerations suggest that r and omized trials are more suitable than uncontrolled experimentation in protecting the interests of patients . R and omized clinical trials remain the most reliable method for evaluating the efficacy of therapies
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 .