Vitamin A is essential for vision, immune function, reproduction, and cellular communication. Our research distinguishes between preformed vitamin A (retinol — from animal sources) and provitamin A (beta-carotene — from plants). The critical safety concern: preformed vitamin A is teratogenic at doses >10,000 IU/day during pregnancy and hepatotoxic with chronic high-dose supplementation. Beta-carotene INCREASES lung cancer risk in smokers. This is one supplement where excess is genuinely dangerous.
Additive vitamin A toxicity — hypervitaminosis A risk
High-dose vitamin A may increase bleeding risk
Additive intracranial pressure (pseudotumor cerebri)
Chronic vitamin A is hepatotoxic; additive liver stress
Reduces fat-soluble vitamin absorption including vitamin A
Reduces absorption
Not Prohibited
Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study Group. The effect of vitamin E and beta carotene on lung cancer (ATBC trial).
Omenn GS et al. Effects of a combination of beta carotene and vitamin A on lung cancer (CARET trial).
Rothman KJ et al. Teratogenicity of high vitamin A intake. *N Engl J Med.* 1995.
(1995). PMID: 7570449
Penniston KL, Tanumihardjo SA. The acute and chronic toxic effects of vitamin A.
Reviewed by the Scan Dose Research Team and Clinical Advisory Board | Last updated: April 2026
Not medical advice. Based on published clinical research and systematic reviews.