Spinach - What my Chemistry Class Says

Seems like my chemistry class is putting up arguments against my nutrition class. My understanding is that spinach is not a good source of Vitamin A either, when compared to animal sources like eggs, the carotenoids don't get absorbed in anything like the same amount.

Here's a paper in The American Journal of Clinical Nutrition looking at the issue

The challenge to reach nutritional adequacy for vitamin A: β-carotene bioavailability and conversion—evidence in humans

So who do I go with - my nutrition textbook or my chemistry one ?