Vitamin E Inadequacy in Humans: Causes and Consequences

It is estimated that >90% of Americans do not consume sufficient dietary vitamin E, as alpha-tocopherol, to meet estimated average requirements. What are the adverse consequences of inadequate dietary alpha-tocopherol intakes? This review discusses health aspects where inadequate vitamin E status is detrimental and additional vitamin E has reversed the symptoms. In general, plasma alpha-tocopherol concentrations <12 mu mol/L are associated with increased infection, anemia, stunting of growth, and poor outcomes during pregnancy for both the infant and the mother. When low dietary amounts of alpha-tocopherol are consumed, tissue alpha-tocopherol needs exceed amounts available, leading to increased damage to target tissues. Seemingly, adequacy of human vitamin E status cannot be assessed from circulating alpha-tocopherol concentrations, but inadequacy can be determined from low values. Circulating alpha-tocopherol concentrations are very difficult to interpret because, as a person ages, plasma lipid concentrations also increase and these elevations in lipids increase the plasma carriers for alpha-tocopherol, leading to higher circulating alpha-tocopherol concentrations. However, abnormal lipoprotein metabolism does not necessarily increase alpha-tocopherol delivery to tissues. Additional biomarkers of inadequate vitamin E status are needed. Urinary excretion of the vitamin E metabolite alpha-carboxy-ethyl-hydroxychromanol may fulfill this biomarker role, but it has not been widely studied with regard to vitamin E status in humans or with regard to health benefits. This review evaluated the information available on the adverse consequences of inadequate alpha-tocopherol status and provides suggestions for avenues for research.