Vitamin B6 status, deficiency and its consequences -: an overview

Background: Vitamin B-6 is thought to be a most versatile coenzyme that participates in more than 100 biochemical reactions. It is involved in amino acid and homocysteine metabolism, glucose and lipid metabolism, neurotransmitter production and DNA/RNA synthesis. Vitamin B-6 can also be a modulator of gene expression. Nowadays, clinically evident vitamin B-6 deficiency is not a common disorder, at least in the general population. Nevertheless, a subclinical, undiagnosed deficiency may be present in some subjects, particularly in the elderly. Objective: This review gives a complete overview over the metabolism and interactions of vitamin B-6 Further, we show which complications and deficiency symptoms can occur due to a lack of vitamin B-6 and possibilities for public health and supplemental interventions. Methods: The database Medline (www.nevi.nlm.nih.gov) was searched for terms like "vitamin B-6", "pyridoxal", "cancer", "homocysteine", etc. For a complete understanding, we included studies with early findings from the forties as well as recent results from 2006. These studies were summarised and compared in different chapters. Results and conclusion: In fact, it has been proposed that suboptimal vitamin B-6 status is associated with certain diseases that particularly afflict the elderly population: impaired cognitive function, Alzheimer's disease, cardiovascular disease, and different types of cancer. Some of these problems may be related to the elevated homocysteine concentrations associated to vitamin B-6 deficiency, but there is also evidence for other mechanisms independent of homocysteine by which a suboptimal vitamin B-6 status could increase the risk for these chronic diseases.