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Reading an article about Vitamin-A:

Vitamin A Fact Sheet for Health Professionals

The following acronym RAE in:

RDAs for vitamin A are given as mcg of retinol activity equivalents (RAE) to account for the different bioactivities of retinol and provitamin A carotenoids (see Table 1). Because the body converts all dietary sources of vitamin A into retinol, 1 mcg of physiologically available retinol is equivalent to the following amounts from dietary sources: 1 mcg of retinol, 12 mcg of beta-carotene, and 24 mcg of alpha-carotene or beta-cryptoxanthin. From dietary supplements, the body converts 2 mcg of beta-carotene to 1 mcg of retinol.

Currently, vitamin A is listed on food and supplement labels in international units (IUs) even though nutrition scientists rarely use this measure. Conversion rates between mcg RAE and IU are as follows [7]:

1 IU retinol = 0.3 mcg RAE
1 IU beta-carotene from dietary supplements = 0.15 mcg RAE
1 IU beta-carotene from food = 0.05 mcg RAE
1 IU alpha-carotene or beta-cryptoxanthin = 0.025 mcg RAE

Can you please explain a bit the diffence between those measurements? :)

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    Welcome to MedicalSciences.SE, volna! Please take the tour and read the help center. This question is a bit unclear to me, as the quote you posted should be the explanation you seek. Please help us to help you and edit your question to provide more information on what you have read on this subject, what made you are ask this question, and any problems you are having understanding your research. If you need help, you can view our How to Ask page. If you could detail a bit more what exactly is unclear to you, someone with an answer will do a better job. Thanks! Sep 23 '18 at 17:10
  • IU = international unit, mcg RAE = microgram retinol activity equivalents (old unit). This explains it a bit.
    – Narusan
    Sep 23 '18 at 18:08

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