Wow.
And this is also a great study for showing how much beta-carotene is actually converted to retinol. They write a minimum of 62% is turned into retinol. So a lot will eventually go the retinol route.
"What is clear is that, by our estimates, a minimum of 62% of the absorbed β-carotene was cleaved to vitamin A and by this reasoning the vitamin A value of β-carotene dose was 0.53. [The calculation is as follows: Assuming central cleavage, 1 mol of β-carotene yields 2 mol of vitamin A. If 62% of the absorbed β-carotene were cleaved to vitamin A, 1 mol of β-carotene would yield 1.24 mol of vitamin A. Thus, the vitamin A value of the absorbed dose is 1.24. Yet, the dose was 42.6% absorbed. So, the actual vitamin A value is (1.24) (0.426) or 0.53.]"
1 molecule of beta-carotene turns into 2 molecules of "active vitamin A".
The 0.53 value means that 1mg of ingested beta-carotene will turn into 0.5mg retinol. In other words, one medium carrot (eaten with lots of fat) can be equivalent to 27g beef liver.
Due to the time-delayed conversion, an acute poisoning is not possible, but a chronic poisoning is.