Conversion factors

Vitamin A

To convert Vitamin A from International Units (IU) to Retinal Equivalents (RE), use the following equation:

1 RE = 3.33 IU (animal sources)

1 RE = 10.00 IU (plant sources)

1 RE = 5.00 IU (average-combination foods)

Vitamin A (RAE)

1 mcg of RAE

= 1 mcg of Retinol

= 2 mcg of Beta Carotene (supplement)

= 12 mcg of Beta Carotene (dietary)

= 24 mcg of other Vitamin A precursor carotenoids

1 IU retinol

= 0.3 mcg of retinol

= 0.3 mcg of RAE

1 IU Beta Carotene supplement

= 0.5 IU retinol

= 0.15 mcg RAE

1 IU Beta Carotene dietary

= 0.165 IU retinol

= 0.05 mcg of RAE

1 IU other Vitamin A precursor carotenoids

=0.025 mcg of RAE.

The above information is taken from Rolfes, S. Pinna, K. Whitney, E. Understanding Normal and Clinical Nutrition. 7th ed. 2006.

Beta-carotene

To convert Beta-Carotene from RE to micrograms, use the following equation:

1 RE = 6 micrograms Beta-Carotene

Vitamin D

To convert Vitamin D from IU to micrograms, use the following equation:

1 IU = 0.025 micrograms

Vitamin E

To convert Vitamin E from IU to milligrams ATE, use the following equation:

1.49 (IU) = 1 milligrams of ATE

To convert to mg of Alpha Tcocopherol

= IU of the (RRR-alpha-tocopherol compound) X 0.67

= IU of the (All rac-alpha-tocopherol compound) X 0.45

In 2000, the Dietary Reference Intake Recommended Dietary Allowance (RDA) for Vitamin E was changed from alpha-tocopherol equivalents (ATE mg) to alpha-tocopherol (mg). Most foods that have a Vitamin E value in our knowledge base do not distinguish between the different tocopherols. Until further updated information can be provided by our food sources to change the Vitamin E (ATE mg) values to alpha-tocopherol values, the alpha-tocopherol values might be incomplete.

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