As far as I can tell, the body synthesises its own Vitamin A easily. Though Wikipedia isn't always accurate, but it's backed up through a quick Google:
Quote:
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Retinol (the animal form of vitamin A) is ingested in a precursor form; animal sources (milk and eggs) contain retinyl esters, whereas plants (carrots, spinach) contain pro-vitamin A carotenoids.
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Retinol - Wikipedia, the free encyclopedia
It goes on to list various foods rich in the precursors, which include liver, eggs, and a whole bunch of vegetables.
EDIT: Not to mention, the animals you eat to get Vitamin had to synthesise vitamin A for themselves anyway, which is why I find arguments along those lines unconvincing -- if they can do it, then we can too. Plus, I've not heard of any vegetarians losing night vision because of a shortage of Vitamin A, which is one of the first things that would happen if you had a deficiency.