Micronutrient concentrations in paired skin and plasma of patients with actinic keratoses: effect of prolonged retinol supplementation

Much of our knowledge about the relationship between micronutrients and cancer comes from studies in which plasma (serum) micronutrient levels have been correlated with cancer incidence; however, the relationship between the concentrations of micronutrients in the plasma and in the target tissues has not been established. Ninety-three subjects (62 males and 31 females ages 42-86, median age 69) with actinic keratoses were recruited for investigation of this relationship. The subjects were randomly assigned and received placebo or retinol (25,000 IU/day) intervention for 48 to 65 months as part of a skin cancer chemoprevention trial. Shortly before the end of the trial, three fasting plasma samples and one skin biopsy were obtained from each subject. The concentrations of lutein, zeaxanthin, beta-cryptoxanthin, lycopene, alpha-carotene, beta-carotene, cis-beta-carotene, retinol, retinyl palmitate, alpha-tocopherol and gamma-tocopherol in the plasma and skin were simultaneously measured using HPLC. The profiles of the eleven micronutrients in the plasma and skin were similar. Lycopene, beta-carotene and alpha-tocopherol were the predominant micronutrients in both plasma and skin, but the ratio of retinyl palmitate to retinol was much greater in the skin than plasma. The three fasting plasma concentrations from the same subject during a one-month period were very consistent; however, the between-person variations were very large. The retinol supplementation caused a significant increase in the plasma concentrations of retinol, retinyl palmitate, lutein and alpha-tocopherol, especially retinyl palmitate as well as the skin concentrations of retinol and retinyl palmitate.