Smith, DM; Pickering, RM; Lewith, GT
Objective: To assess the effectiveness of oral vanadium supplementation for glycaemic control in type 2 diabetes by conducting a systematic review of the literature.
Design and Methods: Eligible studies were identified by searching 14 databases using standardized terms. Experts, study authors and manufacturers were also contacted. Hand-searching was not undertaken. Selection criteria for inclusion in the review were controlled human trials of vanadium vs. placebo in adults with type 2 diabetes of minimum 2 months duration, and a minimum of 10 subjects per arm. Data extraction, assessment of study quality and outcome analysis were undertaken by two independent reviewers.
Results: One hundred and fifty one studies were found but none met the inclusion criteria. We proceeded to summarize the state of existing evidence and plan for a future clinical trial by applying revised, less restrictive criteria to our search, for clinical trials of 30–150 mg daily oral vanadium supplementation in diabetic humans. Only five were identified. These demonstrated significant treatment-effects, but due to poor study quality, must be interpreted with caution. Treatment with vanadium often results in gastrointestinal side-effects.
Conclusion: There is no rigorous evidence that oral vanadium supplementation improves glycaemic control in type 2 diabetes. The routine use of vanadium for this purpose cannot be recommended. A large-scale randomized controlled trial is needed to address this clinical question.
The importance of maintaining rigorous glycaemic control to prevent the chronic complications of type 2 diabetes mellitus is well established.1 The global prevalence of diabetes mellitus is estimated at 246 million,2 most of whom have the type 2 form and live in areas of the world where existing treatments are unavailable or too expensive. Any potential new, inexpensive treatments should therefore be thoroughly investigated in the hope of reducing global diabetic morbidity and mortality. One example is the use of dietary micronutrient supplementation.
There is laboratory evidence for micronutrient deficiency states in type 2 diabetes.3 Equally, diabetes-like disorders of metabolism can be observed in micronutrient deficiency states: in animals hyperglycaemia is a feature of complete exclusion of chromium from the diet;4 low zinc levels are associated with hyperglycaemia and lower insulin levels.5 However, while unconventional nutritionists already advocate micronutrient supplementation in diabetes,6–8 conventional mainstream texts make no mention of it9,,10 and major diabetes charities do not promote this approach.11
This study systematically evaluates the evidence for the clinical effectiveness of one micronutrient, the trace element vanadium. It is present in all tissues, but has not been established as being essential for survival, clinical deficiency states are not described, and its role in glucose metabolism is not understood.3 However, it does have insulin-mimetic properties in liver, skeletal muscle and adipose tissue in-vitro, and in in-vivo animal models, via inhibition of the phosphotyrosine phosphatase (PTP) enzyme system,12,,13 thus suggesting it may have a role in glycaemic control.
This systematic review of the available clinical evidence sought to establish whether dietary vanadium supplementation improves glycaemic control in type 2 diabetes mellitus and could be promoted for use in clinical practice. A secondary aim was to identify adverse events associated with vanadium supplementation.