维生素 A · 单位换算
先选择标签注明的化学形式，再选择换算方向。未选择形式则不给出结果：同一 IU 数值在不同形式下对应的质量不同。
结果
请先选择形式。IU 不是质量单位，未确定形式即不存在可依据的系数。
本页使用的系数
| 形式 | 从 | 到 | 系数 | 来源 | 年份 |
|---|---|---|---|---|---|
| Beta-carotene (vitamin A) | IU | mcg RAE | 0.3 | FDA Guidance for Industry: Converting Units of Measure for Folate, Niacin, and Vitamins A, D, and E on the Nutrition and Supplement Facts Labels | 2019 |
| Beta-carotene (vitamin A) | mcg | mcg RAE | 0.5 | FDA Guidance for Industry: Converting Units of Measure for Folate, Niacin, and Vitamins A, D, and E on the Nutrition and Supplement Facts Labels | 2019 |
| Retinol / retinyl esters, preformed (vitamin A) | IU | mcg RAE | 0.3 | Vitamin A and Carotenoids - Health Professional Fact Sheet (NIH Office of Dietary Supplements) | 未注明年份 |
| Retinol / retinyl esters, preformed (vitamin A) | mcg | mcg RAE | 1 | eCFR — 21 CFR 101.9 Nutrition labeling of food, (c)(8)(iv) footnote 3 | 2016 |
来源原文
Table 3. Conversion factors from vitamin A (IU) to Vitamin A (mcg RAE): Supplemental β-carotene 0.30. [Footnote: 1 IU = 0.6 mcg of β-carotene (Ref. 4), followed by a second step conversion from mcg to vitamin A expressed as mcg RAE (1 mcg RAE = 2 micrograms supplemental β-carotene) (Ref. 5).]
FDA Guidance for Industry: Converting Units of Measure for Folate, Niacin, and Vitamins A, D, and E on the Nutrition and Supplement Facts Labels
Table 2. Conversion factors from pre-formed retinol and provitamin A carotenoids expressed in mcg to vitamin A (mcg RAE): Supplemental β-carotene ÷ 2. [1 mcg RAE = 2 mcg supplemental β-carotene.]
FDA Guidance for Industry: Converting Units of Measure for Folate, Niacin, and Vitamins A, D, and E on the Nutrition and Supplement Facts Labels
The units of measurement for vitamin A are now mcg RAE, but International Units (IUs) were previously used ... To convert IU to mcg RAE, use the following ...: 1 IU retinol = 0.3 mcg RAE. [Exact — this reuses the original fixed biological IU definition (1 IU = 0.3 mcg all-trans-retinol), unchanged when the label unit was renamed to mcg RAE in 2016.]
Vitamin A and Carotenoids - Health Professional Fact Sheet (NIH Office of Dietary Supplements)
RAE = Retinol activity equivalents; 1 microgram RAE = 1 microgram retinol, 2 micrograms supplemental β-carotene, 12 micrograms dietary β-carotene, or 24 micrograms dietary α-carotene, or 24 micrograms dietary β-cryptoxanthin. [Exact — this is the regulatory definition of the mcg RAE unit itself, not an IU conversion. mcg RAE is NOT interchangeable with IU except by first identifying the vitamin A source and applying the separate IU→RAE factors above.]
eCFR — 21 CFR 101.9 Nutrition labeling of food, (c)(8)(iv) footnote 3