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


METHODS
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.
Sibulesky
L
L
Foster Biomedical Research Laboratory, Brandeis University, Waltham, MA, USA.
Hayes
K C
KC
Pronczuk
A
A
Weigel-DiFranco
C
C
Rosner
B
B
Berson
E L
EL
D000293:Adolescent; D000328:Adult; D002851:Chromatography, High Pressure Liquid; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005215:Fasting / Q000097:blood; D005260:Female; D006801:Humans; D008099:Liver / Q000201:enzymology; D008297:Male; D008875:Middle Aged; D012174:Retinitis Pigmentosa / Q000188:drug therapy*; D014280:Triglycerides / Q000097:blood; D014801:Vitamin A / Q000008:administration & dosage* / Q000009:adverse effects / Q000097:blood; D014810:Vitamin E / Q000008:administration & dosage
D014280:Triglycerides; D014801:Vitamin A; D014810:Vitamin E