|MadSci Network: Biochemistry|
Good question Rob, but there isn't an easy answer.
The original international standard for Vit. E (dl-alpha tocopheryl acetate) had one mg equivalent to one IU of Vit. E. This is no longer available.
There are several other compounds or components of Vit. E which are measureable but there is variation of how many IU are equivalent to how many mg.
Vitamin A is no easier... 1 retinol equivalent is equal to 1 microgram of retinol, or 6 micrograms of Beta-carotene or 12 micrograms of other provitamin A cartenoids or 3.33 IU vitamin activity from retinol or 10 IU Vitamin A activity from beta-carotene. This information came from the National Research Council's Recommended Dietary Allowances. Probably, the best bet is accept what is on the label, if you're buying Vit E supplements and it states 400IUs accept this and not worry about how many mg there are. Good luck and I hope I haven't confused you more.
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