Vitamin A Conversion Calculator 1. Enter the number in the appropriate yellow space corresponding to the CURRENT units and then press the Enter key on your keyboard. Only one line should be used at a time . Retinol Equivalents Micrograms Micromoles International Units 2. Read the conversion below Retinol Equivalents Micrograms Micromoles International Units 3. Assumptions 1 retinol equivalent = 1 Micrograms Retinol 0.003491 Micromoles Retinol 3.33 International Units Vitamin A Note: The unit of vitamin A activity is the retinol equivalent (RE), based on the activity of 1 microgram (mg) of all-trans retinol. The International Unit (IU), still used in some contexts, is equal to 0.300 mg of all-trans retinol. The Systeme Internationale (SI) uses molar measures of vitamin A (based on the molecular weight of retinol, such that 1 mg of retinol is equal to 0.003491 moles and 1 mmole of retinol is equal to 286.46 mg. Conversion from one system to another is straightforward as long as the only compound present is retinol. However, when carotenoids with pro-vitamin A activity are present, the situation becomes more complex. Different carotenoids have different levels of vitamin A activity depending upon the efficiency of their absorption and the rate of their conversion to vitamin A. Whereas 1 RE is equal to 1 mg of all-trans retinol, the same level of vitamin A activity required 6 mg of beta-carotene and 12 mg of other carotenoids with vitamin A activity. A number of studies published over the last decade have demonstrated convincingly that the conversion factors used traditionally overestimated the contribution of carotenoids to vitamin A activity. The Institute of Medicine (2001) has recently proposed the retinol activity equivalent (RAE), equal to the activity of 1 mg of all-trans retinol but 12 (not 6) mg of betacarotene and 24 (not 12) mg of other pro-vitamin A carotenoids.
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