is it healthier to eat no meat?

[FlatAssembler]

Why wouldn't free iron (found in lentil, spinach, white meat, fish...) be good for you?

Because free iron is unbound. It can damage organs, facilitate the spreading of cancer cells, cause bad bacteria to flourish and (at very high levels) damage DNA.

Boru

Then why it is that nearly all studies about that show that the heme iron increases the risk of various cancers (most strongly colon cancer), rather than the free iron?