[harimau777]

The page that I linked is about iron, but when I wrote my message I accidentally said "protein". I corrected my post, thanks for the catch.

[chongli]

Vegetable sources of iron are called non-heme iron, in contrast to meat which is heme iron. Heme iron is readily absorbed and used by the body whereas non-heme iron is not [1]. Note that this applies to humans, not other animals. Cows are far better at absorbing these nutrients from plant sources than we are.

[1] https://www.hsph.harvard.edu/nutritionsource/iron/