This chestnut will appeal to the vegetarians. But we should all be aware. It turns out that when your mom told you that you are what you eat, it was more literally true than she probably believed.
Generally, what you eat gets broken down to rather small molecular bits, then built back up into the stuff that you are made of. Despite the fact that both cows and humans have hemoglobin, we don’t just use theirs. When we eat beef, we break down all the cow protein (including hemoglobin) and then build our hemoglobin from the bits.
There are some exceptions, it seems. As covered in a short news piece by Science, the article published in PNAS details the results of a trio of researchers who dosed themselves with pig-gland extract in order to show that a a sialic acid called Neu5Gc (made by pigs but not people) ends up in human tissue.
Since this molecule tends to attract the attention of the immune system, that’s probably a bad thing.
The Big Upshot for today is this: in biology (and in medicine) there are always exceptions.