Large scale trials are needed to ‘definitively’ show that vitamin D can offer benefits across a wide range of health states other than bone disorders, according to experts at the Endocrine Society.
The new scientific statement, published by the global society of experts, examines the state of current into the associations between the sunshine vitamin and non-skeletal disorders such as improved immune function, high blood pressure (hypertension), stroke, skin conditions and maternal and baby health.
The authors, led by Dr Clifford Rosen of Tufts University School of Medicine in the USA said the statement represents the first comprehensive evaluation of both the basic and clinical evidence related to the non-skeletal effects of vitamin D.
“The role of vitamin D supplementation in the prevention and treatment of chronic non-skeletal diseases remains to be determined,” said Rosen, who also chaired the Endocrine Society committee of experts that authored the statement.
“We need large randomized controlled trials and dose-response data to test the effects of vitamin D on chronic disease outcomes including autoimmunity, obesity, diabetes, hypertension and heart disease.”
Lack of data?
Significant controversy has emerged over the last decade concerning the effects of vitamin D on skeletal and non-skeletal tissues.
The demonstration that vitamin D receptors are expressed in virtually all cells in the body, in combination with a growing body of observational data supporting a relationship of serum 25-hydroxyvitamin D to chronic metabolic, cardiovascular, and neoplastic diseases, has led to widespread use of vitamin D supplementation for the prevention and treatment of numerous disorders. However the scientific data to back up such uses still remains scarce, said the statement.
Although observational studies do support ‘a strong case’ for the association between vitamin D and musculoskeletal, cardiovascular, neoplastic, and metabolic disorders, Rosen and his colleagues argue that there remains “a paucity of large-scale and long-term randomised clinical trials.”
“Thus, at this time, more studies are needed to definitively conclude that vitamin D can offer preventive and therapeutic benefits across a wide range of physiological states and chronic non-skeletal disorders.”
The scientific statement outlines the evidence to suggest the effects of vitamin D on epidermal, neuromuscular, maternal/fetal and neoplastic (abnormal growth) tissues.
Rosen and his team critically evaluated the literature for each organ system – using the available evidence from observational studies and randomised trials to define the strength of associations between vitamin D and tissue-specific outcomes.
The authors concluded:
- Topical and oral vitamin D may be useful in treating skin disorders such as psoriasis – though large-scale randomised placebo-controlled clinical trials are needed to demonstrate the efficacy of treatment with vitamin D on skin disorders or the prevention of skin cancer.
- Although the ‘obesity epidemic’ has been associated with a rising levels of vitamin D deficiency, a cause-and-effect relationship has not been established. Strong evidence does not exist to support the idea that vitamin D supplementation reduces the risk of type 2 diabetes or metabolic syndrome, they said.
- Vitamin D supplementation is likely to reduce the risk of falls, particularly in individuals who have low baseline levels (<20 ng/ml) and are supplemented with calcium as well.
- Evidence to suggest vitamin D reduces cancer incidence is inconclusive with regard to causality. They note that observational evidence is strongest for colorectal cancer – data is weak or inconsistent for breast, prostate and total cancer.
- There is a possibility that vitamin D supplementation may lower cardiovascular disease risk. However the experts noted limitations in applying observational data to clinical practice. The lack of evidence from trials does not support recommending vitamin D supplementation for lowering cardiovascular disease risk at this time, they said.
- Clinical trials are needed to test whether vitamin D supplementation during pregnancy will prevent type 1 diabetes in offspring.
Source: Endocrine Reviews
Published online ahead of print, doi: 10.1210/er.2012-1000
“The Nonskeletal Effects of Vitamin D: An Endocrine Society Scientific Statement”
Authors: C.J. Rosen, J.S. Adams, D.D. Bikle, D.M. Black, et al