Influence of fasting on circulating levels of alpha-tocopherol and beta-carotene. Effect of short-term supplementation.

We investigated the influence of fasting on the levels of alpha-tocopherol in plasma, erythrocytes and platelets, and on plasma beta-carotene. Six apparently healthy adults were subjected to 17-h feed-fasting experiments at various days before, during and after supplementation with alpha-tocopherol (455 mg/day, 41 days) and beta-carotene (25 mg/day, 24 days). Adipose tissue alpha-tocopherol and beta-carotene were measured at regular intervals. Supplementation increased alpha-tocopherol and beta-carotene in all compartments, except for beta-carotene in adipose tissue. Discontinuation caused a rapid return to baseline, except for adipose tissue alpha-tocopherol and plasma beta-carotene. Fasting caused linear increases of free fatty acids, consistent (but small) increases of plasma alpha-tocopherol and inconsistent increases of plasma beta-carotene. There were no fasting-related changes in other compartments. We conclude that fasting is unable to increase alpha-tocopherol and beta-carotene in circulating lipoproteins and cells to a considerable extent, both at baseline levels and after short-term supplementation. Maintenance of high levels may necessitate regular high oral intakes.