Optimal nutrition: vitamin E.

Interest in the role of vitamin E in disease prevention has encouraged the search for reliable indices of vitamin E status. Most studies in human subjects make use of static markers, usually alpha-tocopherol concentrations in plasma or serum. Plasma or serum alpha-tocopherol concentrations of < 11.6, 11.6-16.2, and > 16.2 mumol/l are normally regarded as indicating deficient, low and acceptable vitamin E status respectively, although more recently it has been suggested that the optimal plasma alpha-tocopherol concentration for protection against cardiovascular disease and cancer is > 30 mumol/l at common plasma lipid concentrations in combination with plasma vitamin C concentrations of > 50 mumol/l and > 0.4 mumol beta-carotene/l. Assessment of vitamin E status has also been based on alpha-tocopherol concentrations in erythrocytes, lymphocytes, platelets, lipoproteins, adipose tissue, buccal mucosal cells and LDL, and on alpha-tocopherol: gamma-tocopherol in serum or plasma. Erythrocyte susceptibility to haemolysis or lipid oxidation, breath hydrocarbon exhalation, oxidative resistance of LDL, and alpha-tocopheryl quinone concentrations in cerebrospinal fluid have been used as functional markers of vitamin E status. However, many of these tests tend to be non-specific and poorly standardized. The recognition that vitamin E has important roles in platelet, vascular and immune function in addition to its antioxidant properties may lead to the identification of more specific biomarkers of vitamin E status.