Free haem is toxic, so the parasite quickly converts it into an insoluble crystal known as haemozoin.
Nature(Aug 30, 2014)
Not only that but in some bacteria the “haem co-factor” itself can be toxic.
Scientific American(May 05, 2012)
Experts suspect that haem, the pigment which gives red meat its color, damages cells in the digestive system, which may lead to cancer.
Seattle Times(Feb 25, 2011)