Assessment and clinical implications of functional vitamin B6 deficiency

Vitamins are essential for a healthy and long life. From that point of view, vitamin supplements are used with the desire to improve health and prevent disease. However, in many patient groups, such a fibromyalgia and chronic fatigue syndrome, the benefit of vitamin supplementation is not known and many people might unnecessarily be putting themselves at risk of vitamin toxicity. In this thesis, we show that the available studies towards vitamins in fibromyalgia and chronic fatigue syndrome are of low quality and overall do not justify the high use of micronutrients by these patients. Furthermore, we show that deficiency of vitamin B6, a vitamin that is present in virtually all standard multivitamin pills, occurs frequently in stable outpatient kidney transplant recipients, despite adequate vitamin B6 intake through diet. Importantly, this deficient state confers increased risk of long-term mortality due to cardiovascular causes, not only in kidney transplant recipients but also in women from the general population. We therefore conclude that kidney transplant recipients and women may possibly benefit from vitamin B6 supplementation. However, before concrete recommendations can be made, intervention studies involving vitamin B6 supplementation should provide conclusive evidence.