I'd check any source very carefully that says retinol is
non-toxic in overdose. There are many cases in Northern
Canada of poisoning from northern mammal liver, especially
seal and polar bear.
I believe it's only plant carotene that is non-toxic because
we stop converting it to Vitamin A when we have enough.
Cod liver oil has to be balanced in a diet by foods low
in Vitamin A to get balanced nutrition.