Heme iron is connected with an increased rate of colonic adenoma in calcium-deficient mouse models, but this risk disappears when mice are fed adequate calcium.

“studies that have shown that heme iron is connected with increased rate of colonic adenoma which free cancerous growths are done in calcium deficient mouse models nothing in humans and then when they when they feed the mice diets that have adequate amounts of calcium the risk of development of precancerous colon lesions and mics goes away so it's only a calcium deficient mouse model in which you can show that heme iron has any ability to increase the rate of cancerous lesions and it probably has to do with the formation of n nitroso compounds but that's not a very good proxy for a healthy human that calcium deficient mouse model especially when they give the mice adequate calcium and the risk goes away”