Lipid standardization of serum fat-soluble antioxidant concentrations: The YALTA study

Background: Blood lipids can influence fat-soluble antioxidant concentrations and confound their interpretation as indicators of antioxidant intake status and disease risk. Objectives: The objectives were to identify lipoproteins that can confound the interpretation of serum fat-soluble antioxidants, to evaluate the amount of the confounding, and to recommend a method for standardizing blood concentrations of fat-soluble antioxidants. Design: Several methods of lipid standardization of fat-soluble antioxidants were evaluated in a large cohort of young adults with the use of both cross-sectional and longitudinal data analysis. Results: Tocopherol and carotenoid concentrations were associated with plasma total cholesterol and its components, LDL, HDL, and VLDL cholesterol (estimated as plasma total triacylglycerols/5), some of which were independent predictors for all of the fat-soluble antioxidants. Among supplement nonusers, the most amphipathic (polar) of the antioxidants (α-tocopherol, γ-tocopherol, and zeaxanthin plus lutein) and lycopene were associated strongly with these lipid fractions (R² = 0.09, 0.40). Consistent with a causal association in which blood antioxidant concentrations change as blood lipid concentrations change, similar relations were found for changes in blood antioxidant and lipid concentrations over a 7-y period. Concentrations of the remaining carotenoids (β-cryptoxanthin, α-carotene, and β-carotene) had a weaker association with plasma lipoproteins (R² < 0.06). Similar relations were found for supplement users. Conclusions: The simultaneous adjustment of the concentrations of tocopherols, zeaxanthin plus lutein, and lycopene for VLDL, HDL, and LDL cholesterol is recommended. This method is practical and can provide a basis for the standardization of carotenoid and tocopherol concentrations.