http://my.webmd.com/content/article/59/66818.htm

Here is a discussion on the effect of too much vitamin A leading to brittle bones. Is this a recent finding? Or is the jury still out on this one?

I am not sure whether the finidng in regards to brittle bones is new, but Vitamin A poisoning happened a lot to explorers in past centuries, as they ate too much liver from animals they caught and their dogs when they had to eat them.

Some even died, for example the famous Antarcitc Explorer Douglas Mawson.