Vitamin A (Retinol) & Vitamin D

Caution Absorption
Vitamin A (Retinol) → Vitamin D →
Caution Absorption

Very high doses of preformed vitamin A (retinol) may interfere with vitamin D function.

Mechanism

Retinol and calcitriol share some nuclear receptor pathways. High-dose retinol may antagonize vitamin D receptor activity.

Recommendation

This is primarily a concern with preformed vitamin A (retinol) above 10,000 IU/day, not beta-carotene.

Sources

Tolerable upper intake limits

Reference values for safe daily intake of these supplements.

Vitamin A (Retinol)
3000.000 mcg RAE
adults NIH ODS / IOM

Applies to preformed vitamin A (retinol) only, not beta-carotene.

Vitamin D
100.000 mcg (4000 IU)
adults NIH ODS / IOM

Risk of hypercalcemia at very high doses.

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