The international unit (IU) has been used to measure fat-soluble vitamins—vitamin A, D and E—for decades. The IU is an arbitrary amount based on the amount of a given nutrient needed to produce a biological effect. Different than milligram or microgram, the IU measurement describes something that we cannot see; the potency or biological activity of a product. While IU seemed to be an innovative idea during the time it was introduced, many would agree that this IU system is now outdated.
In the new regulation for the nutrition facts label, FDA is replacing the unit “IU” for vitamin A, vitamin D and vitamin E with the metric unit. The unit for vitamin A will be changed to micrograms of retinol activity equivalents (mcg RAE), milligram of alpha-tocopherol (mg) for vitamin E while Vitamin D will be changed to microgram, while the IU reading for Vitamin D could be displayed in parentheses. This regulation will come into effect on Jan. 1, 2020 for companies with US$10 million or more in annual sales; and Jan 1, 2021 for companies with less than $10 million in annual sales. It is expected that other countries will follow this new regulation as well to standardize the labelling system. This new supplement/ nutrition facts label hopefully will help consumers to make a better decision in terms of choosing the right vitamin A and vitamin E for their daily consumption.
Vitamin A is essential vitamin for healthy vision and cellular communication. There are two main ways to obtain vitamin A in the diet, through:
(1) retinols from animal sources and dairy products;
(2) pro-vitamin A carotenoid from plant.
Both retinols and pro-vitamin A carotenoid are metabolized in the body into the active form of vitamin A, retinoic acid. However, retinols and pro-vitamin A carotenoid differ in their bioactivities. As an example, it takes different amount of IU from retinol, beta-carotene from food, beta-carotene from supplement or alpha-carotene to make 1 microgram of retinoic acid.
Therefore, it is vital for consumers to check the source and forms of vitamin A to ensure they get sufficient vitamin A according to the recommended dietary intake (RDI). The RDI of the vitamin A has also changed from 5,000 IU (equivalent to 1,500 mcg RAE) to 900 mcg RAE for males and 700 mcg RAE for females respectively.
The conversion of unit of vitamin A from IU to the metric unit, mcg RAE, will take into account the differences in vitamin A activity between retinols and pro-vitamin A carotenoid. In the new unit, 1 RAE will equal to 1 mcg retinol, 12 mcg beta-carotene, 24 mcg alpha-carotene or 24 mcg beta-cryptoxanthin. Hence, the change of IU to mcg RAE for vitamin A is welcomed as this will reflect the actual or reality of vitamin A activity of its different forms—retinol and pro-vitamin A carotenoid.
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