Population-based study of α- and γ-tocopherol in plasma and adipose tissue as biomarkers of intake in Costa Rican adults

Background: gamma -Tocopherol is the most abundant form of vitamin E in the US diet, but alpha -tocopherol concentrations are the highest in plasma and tissues. Although plasma and adipose tissue concentrations of alpha -tocopherol have been used as biomarkers of intake, the relation between gamma -tocopherol intake and concentrations in plasma and adipose tissue is unknown. Objective: Our goal was to investigate in a randomly selected population from Costa Rica whether plasma or adipose tissue concentrations of alpha- and gamma -tocopherol are suitable biomarkers of intake. Design: A total of 361 men ((x) over bar +/- SD age: 55 +/- 11 y) and 121 women (aged 59 +/- 10 y) completed a 135-item food-frequency questionnaire and provided a fasting blood sample and adipose tissue biopsy sample. Results: Dietary gamma -tocopherol correlated with adipose tissue (r=0.37, P<0.001) and plasma (r=0.42, P<0.001) concentrations, regardless of supplement use. Dietary alpha -tocopherol correlated poorly with adipose tissue (r=0.15, P<0.01) and plasma (r=0.16, P<0.001) concentrations, and these correlations were even lower when users of vitamin supplements (n=24) were excluded (adipose tissue: r=0.10, P<0.05; plasma: r=0.09, P<0.05). Compared with subjects who reported palm shortening (36%) as the major type of fat used for cooking, subjects using soybean oil (52%) had higher amounts of both alpha- and gamma -tocopherol in their diets. However, only gamma -tocopherol concentrations were higher in the plasma and adipose tissue of soybean oil users. Conclusions: Plasma and adipose tissue concentrations of gamma -tocopherol are equally good biomarkers of intake. The weak associations between alpha -tocopherol intake and plasma or adipose tissue concentrations suggest that these biomarkers are influenced more by factors other than alpha -tocopherol intake.