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

Am J Clin Nutr. 1999 Apr;69(4):656-63. doi: 10.1093/ajcn/69.4.656.

Abstract

Background: Vitamin A supplementation is being used successfully to treat some forms of cancer and the degenerative eye disease retinitis pigmentosa. The daily biological need for vitamin A is estimated to be 800 retinol equivalents (RE)/d (2667 IU/d) for adult women and 1000 RE/d (3300 IU/d) for adult men; doses > or = 7500 RE (> or = 25000 IU)/d are considered potentially toxic over the long term.

Objective: We assessed the safety in adults of long-term vitamin A supplementation with doses above the daily biological need but <7500 RE (<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 < or = 12 y (group A) and compared with a similar group (n = 149) that received 23 RE (75 IU)/d (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 (range: 401-3192 RE/d, or 1338-10638 IU/d).

Results: Patients in group A showed an 8% increase in mean serum retinol concentration at 5 y and an 18% increase at 12 y (P < 0.001); no retinol value exceeded the upper normal limit (3.49 micromol/L, or 100 microg/dL). Mean serum retinyl esters were elevated approximately 1.7-fold at 5 y and remained relatively stable thereafter. No clinical symptoms or signs of liver toxicity attributable to vitamin A excess were detected.

Conclusions: Prolonged daily consumption of <7500 RE (<25000 IU) vitamin A/d can be considered safe in this age group.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Chromatography, High Pressure Liquid
  • Dose-Response Relationship, Drug
  • Double-Blind Method
  • Fasting / blood
  • Female
  • Humans
  • Liver / enzymology
  • Male
  • Middle Aged
  • Retinitis Pigmentosa / drug therapy*
  • Triglycerides / blood
  • Vitamin A / administration & dosage*
  • Vitamin A / adverse effects
  • Vitamin A / blood
  • Vitamin E / administration & dosage

Substances

  • Triglycerides
  • Vitamin A
  • Vitamin E