Safety of < 7500RE (< 25000IU) vitamin A daily in adults with retinitis pigmentosa

Background: Vitamin A supplementation is being used successfully to treat s ome forms of cancer and the degenerative eye disease retinitis pigmentosa. The daily biological need for vitamin A is estimated to be 800 retinol equi valents (RE)fd (2667 IU/d) for adult women and 1000 RE/d (3300 IU/d) for ad ult men; doses greater than or equal to 7500 RE (greater than or equal to 2 5000 IU)/d are considered potentially toxic over the long term. Objective: We assessed the safety in adults of long-term vitamin A suppleme ntation with doses above the daily biological need but less than 7500 RE (l ess than 25000 IU)/d. Design: Adults aged 18-54 y with retinitis pigmentosa but in generally good health (n = 146) were supplemented with 4500 RE (15000 IU) vitamin A/d for less than or equal to 12 y (group A) and compared with a similar group (n = 149) that received 23 RE (75 IU)ld (trace group). Mean total consumption of vitamin A in group A was 5583 RE (18609 IU)/d (range: 4911-7296 RE/d, or 16369-24318 IU/d) and that in the trace group was 1053 RE (3511 IU)/d (ran ge: 401-3192 RE/d, or 1338-10638 IU/d). Results: Patients in group A showed an 8% increase in mean serum retinol co ncentration at 5 y and an 18% increase at 12 y (P less than 0.001); no reti nol value exceeded the upper normal limit (3.49 mu mol/L, or 100 mu g/dL). Mean serum retinyl esters were elevated approximate to 1.7-fold at 5 y and remained relatively stable there after. No clinical symptoms or signs of li ver toxicity attributable to vitamin A excess were detected. Conclusions: Prolonged daily consumption of less than 7500 RE (less than 25 000 IU) vitamin A/d can be considered safe in this age group.