REPORTED EFFECTS OF LONG-TERM FREEZER STORAGE ON CONCENTRATIONS OF RETINOL, BETA-CAROTENE, AND ALPHA-TOCOPHEROL IN SERUM OR PLASMA SUMMARIZED

A literature review of the effects of long-term freezer storage on con centrations of antioxidant micronutrients in serum or plasma showed th at a high proportion of the studies that compared the concentrations o f retinol, beta-carotene, or alpha-tocopherol in fresh and stored seru m were deficient because of small numbers of observations, imprecise d escriptions of procedures, and short periods of storage. Data from nes ted case-control studies of the associations of these micronutrients w ith cancer are confounded by differences in the study populations. Nev ertheless, the overall impression is strong that retinol is stable at storage temperatures as warm as -20-degrees-C for at least 15 years, t hat moderate losses of alpha-tocopherol occur at temperatures above -4 0-degrees-C during that period, and that only a small proportion of be ta-carotene persists at storage temperatures above -40-degrees-C. At - 70-degrees-C or colder, all three micronutrients appear to be stable f or at least 15 years.