Retinol in excess of requirements is stored in the liver, bound to proteins, and is a cumulative poison. When the storage capacity is exceeded, free retinol causes damage to cell membranes. Carotene is not toxic in excess, since there is only a limited capacity to form retinol from carotene. The recommended upper limits of habitual daily intake of retinol are about 12.5 × reference intake for adults, but only 2.5 × reference intake for infants. Retinol is also teratogenic in excess, and for pregnant women the recommended upper limit of daily intake is 3 000–3 300 µg.
Subjects: Medicine and Health.